From fb1469d84f409becbd8b24cedaa5b936622052f6 Mon Sep 17 00:00:00 2001
From: Ryan Wyllie <ryan@moodle.com>
Date: Thu, 20 Oct 2016 06:01:57 +0000
Subject: [PATCH 1/3] MDL-56139 message: ajax poll for new messages in message
 area

---
 lang/en/cache.php                             |   1 +
 lib/amd/build/backoff_timer.min.js            |   1 +
 lib/amd/src/backoff_timer.js                  | 206 ++++++++++++++++++
 lib/db/caches.php                             |   9 +
 lib/messagelib.php                            |  10 +
 .../amd/build/message_area_messages.min.js    |   2 +-
 message/amd/src/message_area_messages.js      | 145 +++++++++++-
 message/classes/api.php                       |  25 ++-
 message/classes/helper.php                    |  31 ++-
 .../message_last_created_cache_source.php     |  89 ++++++++
 .../classes/output/messagearea/message.php    |   1 +
 message/externallib.php                       |  32 ++-
 message/tests/api_test.php                    | 125 +++++++++++
 message/tests/externallib_test.php            |  40 ++++
 version.php                                   |   4 +-
 15 files changed, 697 insertions(+), 24 deletions(-)
 create mode 100644 lib/amd/build/backoff_timer.min.js
 create mode 100644 lib/amd/src/backoff_timer.js
 create mode 100644 message/classes/message_last_created_cache_source.php

diff --git a/lang/en/cache.php b/lang/en/cache.php
index 99e33102e7d33..ae490cbaadb1e 100644
--- a/lang/en/cache.php
+++ b/lang/en/cache.php
@@ -52,6 +52,7 @@
 $string['cachedef_groupdata'] = 'Course group information';
 $string['cachedef_htmlpurifier'] = 'HTML Purifier - cleaned content';
 $string['cachedef_langmenu'] = 'List of available languages';
+$string['cachedef_message_last_created'] = 'Time created for most recent message between users';
 $string['cachedef_locking'] = 'Locking';
 $string['cachedef_message_processors_enabled'] = "Message processors enabled status";
 $string['cachedef_navigation_expandcourse'] = 'Navigation expandable courses';
diff --git a/lib/amd/build/backoff_timer.min.js b/lib/amd/build/backoff_timer.min.js
new file mode 100644
index 0000000000000..b1d81162ea102
--- /dev/null
+++ b/lib/amd/build/backoff_timer.min.js
@@ -0,0 +1 @@
+define(function(){var a=1e3,b=function(b,c){if(!b)return a;if(c.length){var d=c[c.length-1];return b+d}return a},c=function(a){this.reset(),this.setCallback(a),this.setBackOffFunction(b)};return c.prototype.setCallback=function(a){return this.callback=a,this},c.prototype.getCallback=function(){return this.callback},c.prototype.setBackOffFunction=function(a){return this.backOffFunction=a,this},c.prototype.getBackOffFunction=function(){return this.backOffFunction},c.prototype.generateNextTime=function(){var a=this.getBackOffFunction().call(this.getBackOffFunction(),this.time,this.previousTimes);return this.previousTimes.push(this.time),this.time=a,a},c.prototype.reset=function(){return this.time=null,this.previousTimes=[],this.stop(),this},c.prototype.stop=function(){return this.timeout&&(window.clearTimeout(this.timeout),this.timeout=null),this},c.prototype.start=function(){if(!this.timeout){var a=this.generateNextTime();this.timeout=window.setTimeout(function(){this.getCallback().call(),this.stop(),this.start()}.bind(this),a)}return this},c.prototype.restart=function(){return this.reset().start()},c});
\ No newline at end of file
diff --git a/lib/amd/src/backoff_timer.js b/lib/amd/src/backoff_timer.js
new file mode 100644
index 0000000000000..992a322d70660
--- /dev/null
+++ b/lib/amd/src/backoff_timer.js
@@ -0,0 +1,206 @@
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * A timer that will execute a callback with decreasing frequency. Useful for
+ * doing polling on the server without overwhelming it with requests.
+ *
+ * @module     core/backoff_timer
+ * @class      backoff_timer
+ * @package    core
+ * @copyright  2016 Ryan Wyllie <ryan@moodle.com>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+define(function() {
+
+    // Default to one second.
+    var DEFAULT_TIME = 1000;
+
+    /**
+     * The default back off function for the timer. It uses the Fibonacci
+     * sequence to determine what the next timeout value should be.
+     *
+     * @param {(int|null)} time The current timeout value or null if none set
+     * @param {array} previousTimes An array containing all previous timeout values
+     * @return {int} The new timeout value
+     */
+    var fibonacciBackOff = function(time, previousTimes) {
+        if (!time) {
+            return DEFAULT_TIME;
+        }
+
+        if (previousTimes.length) {
+            var lastTime = previousTimes[previousTimes.length - 1];
+            return time + lastTime;
+        } else {
+            return DEFAULT_TIME;
+        }
+    };
+
+    /**
+     * Constructor for the back off timer.
+     *
+     * @param {function} callback The function to execute after each tick
+     */
+    var Timer = function(callback) {
+        this.reset();
+        this.setCallback(callback);
+        // Set the default backoff function to be the Fibonacci sequence.
+        this.setBackOffFunction(fibonacciBackOff);
+    };
+
+    /**
+     * Set the callback function to be executed after each tick of the
+     * timer.
+     *
+     * @method setCallback
+     * @param {function} callback The callback function
+     * @return {object} this
+     */
+    Timer.prototype.setCallback = function(callback) {
+        this.callback = callback;
+
+        return this;
+    };
+
+    /**
+     * Get the callback function for this timer.
+     *
+     * @method getCallback
+     * @return {function}
+     */
+    Timer.prototype.getCallback = function() {
+        return this.callback;
+    };
+
+    /**
+     * Set the function to be used when calculating the back off time
+     * for each tick of the timer.
+     *
+     * The back off function will be given two parameters: the current
+     * time and an array containing all previous times.
+     *
+     * @method setBackOffFunction
+     * @param {function} backOffFunction The function to calculate back off times
+     * @return {object} this
+     */
+    Timer.prototype.setBackOffFunction = function(backOffFunction) {
+        this.backOffFunction = backOffFunction;
+
+        return this;
+    };
+
+    /**
+     * Get the current back off function.
+     *
+     * @method getBackOffFunction
+     * @return {function}
+     */
+    Timer.prototype.getBackOffFunction = function() {
+        return this.backOffFunction;
+    };
+
+    /**
+     * Generate the next timeout in the back off time sequence
+     * for the timer.
+     *
+     * The back off function is called to calculate the next value.
+     * It is given the current value and an array of all previous values.
+     *
+     * @method generateNextTime
+     * @return {int} The new timeout value (in milliseconds)
+     */
+    Timer.prototype.generateNextTime = function() {
+        var newTime = this.getBackOffFunction().call(
+            this.getBackOffFunction(),
+            this.time,
+            this.previousTimes
+        );
+        this.previousTimes.push(this.time);
+        this.time = newTime;
+
+        return newTime;
+    };
+
+    /**
+     * Stop the current timer and clear the previous time values
+     *
+     * @method reset
+     * @return {object} this
+     */
+    Timer.prototype.reset = function() {
+        this.time = null;
+        this.previousTimes = [];
+        this.stop();
+
+        return this;
+    };
+
+    /**
+     * Clear the current timeout, if one is set.
+     *
+     * @method stop
+     * @return {object} this
+     */
+    Timer.prototype.stop = function() {
+        if (this.timeout) {
+            window.clearTimeout(this.timeout);
+            this.timeout = null;
+        }
+
+        return this;
+    };
+
+    /**
+     * Start the current timer by generating the new timeout value and
+     * starting the ticks.
+     *
+     * This function recurses after each tick with a new timeout value
+     * generated each time.
+     *
+     * The callback function is called after each tick.
+     *
+     * @method start
+     * @return {object} this
+     */
+    Timer.prototype.start = function() {
+        // If we haven't already started.
+        if (!this.timeout) {
+            var time = this.generateNextTime();
+            this.timeout = window.setTimeout(function() {
+                this.getCallback().call();
+                // Clear the existing timer.
+                this.stop();
+                // Start the next timer.
+                this.start();
+            }.bind(this), time);
+        }
+
+        return this;
+    };
+
+    /**
+     * Reset the timer and start it again from the initial timeout
+     * values
+     *
+     * @method restart
+     * @return {object} this
+     */
+    Timer.prototype.restart = function() {
+        return this.reset().start();
+    };
+
+    return Timer;
+});
diff --git a/lib/db/caches.php b/lib/db/caches.php
index b709f06f0615d..49e509a818654 100644
--- a/lib/db/caches.php
+++ b/lib/db/caches.php
@@ -301,4 +301,13 @@
         'staticacceleration' => true,
         'staticaccelerationsize' => 3
     ),
+
+    // Cache for storing the user's last received message time.
+    'message_last_created' => array(
+        'mode' => cache_store::MODE_APPLICATION,
+        'simplekeys' => true, // The id of the sender and recipient is used.
+        'simplevalues' => true,
+        'datasource' => 'message_last_created_cache_source',
+        'datasourcefile' => 'message/classes/message_last_created_cache_source.php'
+    ),
 );
diff --git a/lib/messagelib.php b/lib/messagelib.php
index 34e7c38ae927a..9bfad534db6f4 100644
--- a/lib/messagelib.php
+++ b/lib/messagelib.php
@@ -234,6 +234,16 @@ function message_send($eventdata) {
         }
     }
 
+    // Only cache messages, not notifications.
+    if (empty($savemessage->notification)) {
+        // Cache the timecreated value of the last message between these two users.
+        $cache = cache::make('core', 'message_last_created');
+        $ids = [$savemessage->useridfrom, $savemessage->useridto];
+        sort($ids);
+        $key = implode('_', $ids);
+        $cache->set($key, $savemessage->timecreated);
+    }
+
     // Store unread message just in case we get a fatal error any time later.
     $savemessage->id = $DB->insert_record('message', $savemessage);
     $eventdata->savedmessageid = $savemessage->id;
diff --git a/message/amd/build/message_area_messages.min.js b/message/amd/build/message_area_messages.min.js
index 79d87c85fd429..4ba61b0677a40 100644
--- a/message/amd/build/message_area_messages.min.js
+++ b/message/amd/build/message_area_messages.min.js
@@ -1 +1 @@
-define(["jquery","core/ajax","core/templates","core/notification","core/custom_interaction_events","core/auto_rows","core_message/message_area_actions","core/modal_factory","core/modal_events","core/str","core_message/message_area_events"],function(a,b,c,d,e,f,g,h,i,j,k){function l(a){this.messageArea=a,this._init()}var m=500,n=50,o={BLOCKTIME:"[data-region='blocktime']",CANCELDELETEMESSAGES:"[data-action='cancel-delete-messages']",CONTACT:"[data-region='contact']",CONVERSATIONS:"[data-region='contacts'][data-region-content='conversations']",DELETEALLMESSAGES:"[data-action='delete-all-messages']",DELETEMESSAGES:"[data-action='delete-messages']",LOADINGICON:".loading-icon",MESSAGE:"[data-region='message']",MESSAGERESPONSE:"[data-region='response']",MESSAGES:"[data-region='messages']",MESSAGESAREA:"[data-region='messages-area']",MESSAGINGAREA:"[data-region='messaging-area']",SENDMESSAGE:"[data-action='send-message']",SENDMESSAGETEXT:"[data-region='send-message-txt']",SHOWCONTACTS:"[data-action='show-contacts']",STARTDELETEMESSAGES:"[data-action='start-delete-messages']"};return l.prototype._isSendingMessage=!1,l.prototype._isLoadingMessages=!1,l.prototype._numMessagesDisplayed=0,l.prototype._numMessagesToRetrieve=20,l.prototype._confirmationModal=null,l.prototype.messageArea=null,l.prototype._init=function(){e.define(this.messageArea.node,[e.events.activate,e.events.up,e.events.down,e.events.enter]),a(window).height()<=670&&(m=400),f.init(this.messageArea.node),this.messageArea.onCustomEvent(k.CONVERSATIONSELECTED,this._viewMessages.bind(this)),this.messageArea.onCustomEvent(k.SENDMESSAGE,this._viewMessages.bind(this)),this.messageArea.onCustomEvent(k.CHOOSEMESSAGESTODELETE,this._chooseMessagesToDelete.bind(this)),this.messageArea.onCustomEvent(k.CANCELDELETEMESSAGES,this._hideDeleteAction.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,o.SENDMESSAGE,this._sendMessage.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,o.STARTDELETEMESSAGES,this._startDeleting.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,o.DELETEMESSAGES,this._deleteMessages.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,o.DELETEALLMESSAGES,this._deleteAllMessages.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,o.CANCELDELETEMESSAGES,this._triggerCancelMessagesToDelete.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,o.MESSAGE,this._toggleMessage.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,o.SHOWCONTACTS,this._hideMessagingArea.bind(this)),this.messageArea.onDelegateEvent(e.events.up,o.MESSAGE,this._selectPreviousMessage.bind(this)),this.messageArea.onDelegateEvent(e.events.down,o.MESSAGE,this._selectNextMessage.bind(this)),this.messageArea.onDelegateEvent("focus",o.SENDMESSAGETEXT,this._setMessaging.bind(this)),this.messageArea.onDelegateEvent("blur",o.SENDMESSAGETEXT,this._clearMessaging.bind(this)),this.messageArea.onDelegateEvent(e.events.enter,o.SENDMESSAGETEXT,this._sendMessageHandler.bind(this)),a(document).on(f.events.ROW_CHANGE,this._adjustMessagesAreaHeight.bind(this));var b=this.messageArea.find(o.MESSAGES);b.length&&this._addScrollEventListener(b.find(o.MESSAGE).length)},l.prototype._viewMessages=function(e,f){this._numMessagesDisplayed=0;var g=b.call([{methodname:"core_message_mark_all_messages_as_read",args:{useridto:this.messageArea.getCurrentUserId(),useridfrom:f}}]),h=0;return c.render("core/loading",{}).then(function(a,b){return c.replaceNodeContents(this.messageArea.find(o.MESSAGESAREA),a,b),g[0]}.bind(this)).then(function(){var b=this.messageArea.find(o.CONVERSATIONS+" "+o.CONTACT+"[data-userid='"+f+"']");return b.hasClass("unread")&&(b.removeClass("unread"),a(document).trigger("messagearea:conversationselected",f)),this._getMessages(f)}.bind(this)).then(function(a){return h=a.messages.length,c.render("core_message/message_area_messages_area",a)}).then(function(a,b){c.replaceNodeContents(this.messageArea.find(o.MESSAGESAREA),a,b),this._addScrollEventListener(h)}.bind(this)).fail(d.exception)},l.prototype._loadMessages=function(){if(this._isLoadingMessages)return!1;this._isLoadingMessages=!0;var b=0;return c.render("core/loading",{}).then(function(a,b){return c.prependNodeContents(this.messageArea.find(o.MESSAGES),"<div style='text-align:center'>"+a+"</div>",b),this._getMessages(this._getUserId())}.bind(this)).then(function(a){return b=a.messages.length,c.render("core_message/message_area_messages",a)}).then(function(d,e){if(this.messageArea.find(o.MESSAGES+" "+o.LOADINGICON).remove(),b>0){var f=this.messageArea.node.find(o.BLOCKTIME+":first"),g=a(d).find(o.BLOCKTIME+":first").addBack();f.html()==g.html()&&f.remove();var h=this.messageArea.find(o.MESSAGES)[0].scrollHeight;c.prependNodeContents(this.messageArea.find(o.MESSAGES),d,e);var i=this.messageArea.find(o.MESSAGES)[0].scrollHeight;this.messageArea.find(o.MESSAGES).scrollTop(i-h),this._numMessagesDisplayed+=b}this._isLoadingMessages=!1}.bind(this)).fail(d.exception)},l.prototype._getMessages=function(a){var c=b.call([{methodname:"core_message_data_for_messagearea_messages",args:{currentuserid:this.messageArea.getCurrentUserId(),otheruserid:a,limitfrom:this._numMessagesDisplayed,limitnum:this._numMessagesToRetrieve,newest:!0}}]);return c[0]},l.prototype._sendMessage=function(){var a=this.messageArea.find(o.SENDMESSAGETEXT),c=a.val();if(""===c.trim())return!1;if(this._isSendingMessage)return!1;this._isSendingMessage=!0;var e=b.call([{methodname:"core_message_send_instant_messages",args:{messages:[{touserid:this._getUserId(),text:c}]}}]);return a.prop("disabled",!0),e[0].then(function(a){if(a.length<0)throw new Error("Invalid response");if(a[0].errormessage)throw new Error(a[0].errormessage);return this.messageArea.trigger(k.MESSAGESENT,[this._getUserId(),c]),this._addMessageToDom()}.bind(this)).then(function(){this._isSendingMessage=!1}.bind(this)).always(function(){a.prop("disabled",!1)}).fail(d.exception)},l.prototype._chooseMessagesToDelete=function(){this.messageArea.find(o.MESSAGESAREA).addClass("editing"),this.messageArea.find(o.MESSAGE).attr("role","checkbox").attr("aria-checked","false")},l.prototype._deleteMessages=function(){var c=this.messageArea.getCurrentUserId(),e=this.messageArea.find(o.MESSAGE+"[aria-checked='true']"),f=[],g=[];e.each(function(b,d){var e=a(d),h=e.data("messageid"),i=e.data("messageread")?1:0;g.push(e),f.push({methodname:"core_message_delete_message",args:{messageid:h,userid:c,read:i}})}),f.length>0?b.call(f)[f.length-1].then(function(){var b=null,c=this.messageArea.find(o.MESSAGE),d=c.last(),e=g[g.length-1];a.each(g,function(a,b){b.remove()}),d.data("id")===e.data("id")&&(b=this.messageArea.find(o.MESSAGE).last()),a.each(g,function(a,b){var c=b.data("blocktime");0===this.messageArea.find(o.MESSAGE+"[data-blocktime='"+c+"']").length&&this.messageArea.find(o.BLOCKTIME+"[data-blocktime='"+c+"']").remove()}.bind(this)),0===this.messageArea.find(o.MESSAGE).length&&this.messageArea.find(o.CONVERSATIONS+" "+o.CONTACT+"[data-userid='"+this._getUserId()+"']").remove(),this.messageArea.trigger(k.MESSAGESDELETED,[this._getUserId(),b])}.bind(this),d.exception):this.messageArea.trigger(k.MESSAGESDELETED,this._getUserId()),this._hideDeleteAction()},l.prototype._addScrollEventListener=function(a){this._scrollBottom(),this._numMessagesDisplayed=a,e.define(this.messageArea.find(o.MESSAGES),[e.events.scrollTop]),this.messageArea.onCustomEvent(e.events.scrollTop,this._loadMessages.bind(this))},l.prototype._deleteAllMessages=function(){this._confirmationModal?this._confirmationModal.show():j.get_strings([{key:"confirm"},{key:"deleteallconfirm",component:"message"}]).done(function(a){h.create({title:a[0],type:h.types.CONFIRM,body:a[1]},this.messageArea.find(o.DELETEALLMESSAGES)).done(function(a){this._confirmationModal=a,a.getRoot().on(i.yes,function(){var a=this._getUserId(),c={methodname:"core_message_delete_conversation",args:{userid:this.messageArea.getCurrentUserId(),otheruserid:a}};b.call([c])[0].then(function(){this.messageArea.find(o.MESSAGESAREA).empty(),this.messageArea.trigger(k.CONVERSATIONDELETED,a),this._hideDeleteAction()}.bind(this),d.exception)}.bind(this)),a.show()}.bind(this))}.bind(this))},l.prototype._hideDeleteAction=function(){this.messageArea.find(o.MESSAGE).removeAttr("role").removeAttr("aria-checked"),this.messageArea.find(o.MESSAGESAREA).removeClass("editing")},l.prototype._triggerCancelMessagesToDelete=function(){this.messageArea.trigger(k.CANCELDELETEMESSAGES)},l.prototype._addMessageToDom=function(){var a=b.call([{methodname:"core_message_data_for_messagearea_get_most_recent_message",args:{currentuserid:this.messageArea.getCurrentUserId(),otheruserid:this._getUserId()}}]);return a[0].then(function(a){return c.render("core_message/message_area_message",a)}).then(function(a,b){c.appendNodeContents(this.messageArea.find(o.MESSAGES),a,b),this.messageArea.find(o.SENDMESSAGETEXT).val("").trigger("input"),this._scrollBottom()}.bind(this)).fail(d.exception)},l.prototype._getUserId=function(){return this.messageArea.find(o.MESSAGES).data("userid")},l.prototype._scrollBottom=function(){var a=this.messageArea.find(o.MESSAGES);0!==a.length&&a.scrollTop(a[0].scrollHeight)},l.prototype._selectPreviousMessage=function(b,c){var d=a(b.target).closest(o.MESSAGE);do d=d.prev();while(d.length&&!d.is(o.MESSAGE));d.focus(),c.originalEvent.preventDefault(),c.originalEvent.stopPropagation()},l.prototype._selectNextMessage=function(b,c){var d=a(b.target).closest(o.MESSAGE);do d=d.next();while(d.length&&!d.is(o.MESSAGE));d.focus(),c.originalEvent.preventDefault(),c.originalEvent.stopPropagation()},l.prototype._setMessaging=function(b){a(b.target).closest(o.MESSAGERESPONSE).addClass("messaging")},l.prototype._clearMessaging=function(b){a(b.target).closest(o.MESSAGERESPONSE).removeClass("messaging")},l.prototype._startDeleting=function(a){var b=new g(this.messageArea);b.chooseMessagesToDelete(),a.preventDefault()},l.prototype._isEditing=function(){return this.messageArea.find(o.MESSAGESAREA).hasClass("editing")},l.prototype._toggleMessage=function(b){if(this._isEditing()){var c=a(b.target).closest(o.MESSAGE);"true"===c.attr("aria-checked")?c.attr("aria-checked","false"):c.attr("aria-checked","true")}},l.prototype._adjustMessagesAreaHeight=function(){var a=this.messageArea.find(o.MESSAGES),b=this.messageArea.find(o.MESSAGERESPONSE),c=b.outerHeight(),d=c-n,e=m-d;a.outerHeight(e)},l.prototype._sendMessageHandler=function(a,b){b.originalEvent.preventDefault(),this._sendMessage()},l.prototype._hideMessagingArea=function(){this.messageArea.find(o.MESSAGINGAREA).removeClass("show-messages").addClass("hide-messages")},l});
\ No newline at end of file
+define(["jquery","core/ajax","core/templates","core/notification","core/custom_interaction_events","core/auto_rows","core_message/message_area_actions","core/modal_factory","core/modal_events","core/str","core_message/message_area_events","core/backoff_timer"],function(a,b,c,d,e,f,g,h,i,j,k,l){function m(a){this.messageArea=a,this._init()}var n=500,o=50,p={BLOCKTIME:"[data-region='blocktime']",CANCELDELETEMESSAGES:"[data-action='cancel-delete-messages']",CONTACT:"[data-region='contact']",CONVERSATIONS:"[data-region='contacts'][data-region-content='conversations']",DELETEALLMESSAGES:"[data-action='delete-all-messages']",DELETEMESSAGES:"[data-action='delete-messages']",LOADINGICON:".loading-icon",MESSAGE:"[data-region='message']",MESSAGERESPONSE:"[data-region='response']",MESSAGES:"[data-region='messages']",MESSAGESAREA:"[data-region='messages-area']",MESSAGINGAREA:"[data-region='messaging-area']",SENDMESSAGE:"[data-action='send-message']",SENDMESSAGETEXT:"[data-region='send-message-txt']",SHOWCONTACTS:"[data-action='show-contacts']",STARTDELETEMESSAGES:"[data-action='start-delete-messages']"};return m.prototype._isSendingMessage=!1,m.prototype._isLoadingMessages=!1,m.prototype._numMessagesDisplayed=0,m.prototype._numMessagesToRetrieve=20,m.prototype._confirmationModal=null,m.prototype._earliestMessageTimestamp=0,m.prototype._timer=null,m.prototype.messageArea=null,m.prototype._init=function(){e.define(this.messageArea.node,[e.events.activate,e.events.up,e.events.down,e.events.enter]),a(window).height()<=670&&(n=400),f.init(this.messageArea.node),this.messageArea.onCustomEvent(k.CONVERSATIONSELECTED,this._viewMessages.bind(this)),this.messageArea.onCustomEvent(k.SENDMESSAGE,this._viewMessages.bind(this)),this.messageArea.onCustomEvent(k.CHOOSEMESSAGESTODELETE,this._chooseMessagesToDelete.bind(this)),this.messageArea.onCustomEvent(k.CANCELDELETEMESSAGES,this._hideDeleteAction.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.SENDMESSAGE,this._sendMessage.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.STARTDELETEMESSAGES,this._startDeleting.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.DELETEMESSAGES,this._deleteMessages.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.DELETEALLMESSAGES,this._deleteAllMessages.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.CANCELDELETEMESSAGES,this._triggerCancelMessagesToDelete.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.MESSAGE,this._toggleMessage.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.SHOWCONTACTS,this._hideMessagingArea.bind(this)),this.messageArea.onDelegateEvent(e.events.up,p.MESSAGE,this._selectPreviousMessage.bind(this)),this.messageArea.onDelegateEvent(e.events.down,p.MESSAGE,this._selectNextMessage.bind(this)),this.messageArea.onDelegateEvent("focus",p.SENDMESSAGETEXT,this._setMessaging.bind(this)),this.messageArea.onDelegateEvent("blur",p.SENDMESSAGETEXT,this._clearMessaging.bind(this)),this.messageArea.onDelegateEvent(e.events.enter,p.SENDMESSAGETEXT,this._sendMessageHandler.bind(this)),a(document).on(f.events.ROW_CHANGE,this._adjustMessagesAreaHeight.bind(this));var b=this.messageArea.find(p.MESSAGES);b.length&&this._addScrollEventListener(b.find(p.MESSAGE).length),this._timer=new l(function(){this._loadNewMessages()}.bind(this)),this._timer.start()},m.prototype._viewMessages=function(e,f){this._numMessagesDisplayed=0,this._timer.stop(),this._earliestMessageTimestamp=0;var g=b.call([{methodname:"core_message_mark_all_messages_as_read",args:{useridto:this.messageArea.getCurrentUserId(),useridfrom:f}}]),h=0;return c.render("core/loading",{}).then(function(a,b){return c.replaceNodeContents(this.messageArea.find(p.MESSAGESAREA),a,b),g[0]}.bind(this)).then(function(){var b=this.messageArea.find(p.CONVERSATIONS+" "+p.CONTACT+"[data-userid='"+f+"']");return b.hasClass("unread")&&(b.removeClass("unread"),a(document).trigger("messagearea:conversationselected",f)),this._getMessages(f)}.bind(this)).then(function(a){return h=a.messages.length,c.render("core_message/message_area_messages_area",a)}).then(function(a,b){c.replaceNodeContents(this.messageArea.find(p.MESSAGESAREA),a,b),this._addScrollEventListener(h),this._timer.restart()}.bind(this)).fail(d.exception)},m.prototype._loadMessages=function(){if(this._isLoadingMessages)return!1;this._isLoadingMessages=!0;var b=0;return c.render("core/loading",{}).then(function(a,b){return c.prependNodeContents(this.messageArea.find(p.MESSAGES),"<div style='text-align:center'>"+a+"</div>",b),this._getMessages(this._getUserId())}.bind(this)).then(function(a){return b=a.messages.length,c.render("core_message/message_area_messages",a)}).then(function(d,e){if(this.messageArea.find(p.MESSAGES+" "+p.LOADINGICON).remove(),b>0){var f=this.messageArea.node.find(p.BLOCKTIME+":first"),g=a(d).find(p.BLOCKTIME+":first").addBack();f.html()==g.html()&&f.remove();var h=this.messageArea.find(p.MESSAGES)[0].scrollHeight;c.prependNodeContents(this.messageArea.find(p.MESSAGES),d,e);var i=this.messageArea.find(p.MESSAGES)[0].scrollHeight;this.messageArea.find(p.MESSAGES).scrollTop(i-h),this._numMessagesDisplayed+=b}this._isLoadingMessages=!1}.bind(this)).fail(d.exception)},m.prototype._loadNewMessages=function(){if(this._isLoadingMessages)return!1;if(!this._getUserId())return!1;this._isLoadingMessages=!0;var b=!1,e=this.messageArea.find(p.MESSAGES);if(0!==e.length){var f=e.scrollTop(),g=e.innerHeight(),h=e[0].scrollHeight;f+g>=h&&(b=!0)}var i=0;return this._getMessages(this._getUserId(),!0).then(function(a){var b=this.messageArea.find(p.MESSAGES);return a.messages=a.messages.filter(function(a){var c=""+a.id+a.isread,d=b.find(p.MESSAGE+'[data-id="'+c+'"]');return!d.length}),i=a.messages.length,c.render("core_message/message_area_messages",a)}.bind(this)).then(function(d,e){i>0&&(d=a(d),d.find(p.BLOCKTIME).remove(),c.appendNodeContents(this.messageArea.find(p.MESSAGES),d,e),b&&this._scrollBottom(),this._numMessagesDisplayed+=i,this._timer.restart())}.bind(this)).always(function(){this._isLoadingMessages=!1}.bind(this)).fail(d.exception)},m.prototype._getMessages=function(a,c){var e={currentuserid:this.messageArea.getCurrentUserId(),otheruserid:a,limitfrom:this._numMessagesDisplayed,limitnum:this._numMessagesToRetrieve,newest:!0};c&&(e.createdfrom=this._earliestMessageTimestamp,e.limitfrom=0,e.limitnum=0);var f=b.call([{methodname:"core_message_data_for_messagearea_messages",args:e}]);return f[0].then(function(a){var b=a.messages;if(b&&b.length){var c=b[b.length-1];this._earliestMessageTimestamp?c.timecreated<this._earliestMessageTimestamp&&(this._earliestMessageTimestamp=c.timecreated+1):this._earliestMessageTimestamp=c.timecreated+1}return a}.bind(this)).fail(function(){this._timer.stop()}.bind(this)).fail(d.exception)},m.prototype._sendMessage=function(){var a=this.messageArea.find(p.SENDMESSAGETEXT),c=a.val();if(""===c.trim())return!1;if(this._isSendingMessage)return!1;this._isSendingMessage=!0;var e=b.call([{methodname:"core_message_send_instant_messages",args:{messages:[{touserid:this._getUserId(),text:c}]}}]);return a.prop("disabled",!0),e[0].then(function(a){if(a.length<0)throw new Error("Invalid response");if(a[0].errormessage)throw new Error(a[0].errormessage);return this.messageArea.trigger(k.MESSAGESENT,[this._getUserId(),c]),this._addMessageToDom()}.bind(this)).then(function(){this._isSendingMessage=!1}.bind(this)).always(function(){a.prop("disabled",!1)}).fail(d.exception)},m.prototype._chooseMessagesToDelete=function(){this.messageArea.find(p.MESSAGESAREA).addClass("editing"),this.messageArea.find(p.MESSAGE).attr("role","checkbox").attr("aria-checked","false")},m.prototype._deleteMessages=function(){var c=this.messageArea.getCurrentUserId(),e=this.messageArea.find(p.MESSAGE+"[aria-checked='true']"),f=[],g=[];e.each(function(b,d){var e=a(d),h=e.data("messageid"),i=e.data("messageread")?1:0;g.push(e),f.push({methodname:"core_message_delete_message",args:{messageid:h,userid:c,read:i}})}),f.length>0?b.call(f)[f.length-1].then(function(){var b=null,c=this.messageArea.find(p.MESSAGE),d=c.last(),e=g[g.length-1];a.each(g,function(a,b){b.remove()}),d.data("id")===e.data("id")&&(b=this.messageArea.find(p.MESSAGE).last()),a.each(g,function(a,b){var c=b.data("blocktime");0===this.messageArea.find(p.MESSAGE+"[data-blocktime='"+c+"']").length&&this.messageArea.find(p.BLOCKTIME+"[data-blocktime='"+c+"']").remove()}.bind(this)),0===this.messageArea.find(p.MESSAGE).length&&this.messageArea.find(p.CONVERSATIONS+" "+p.CONTACT+"[data-userid='"+this._getUserId()+"']").remove(),this.messageArea.trigger(k.MESSAGESDELETED,[this._getUserId(),b])}.bind(this),d.exception):this.messageArea.trigger(k.MESSAGESDELETED,this._getUserId()),this._hideDeleteAction()},m.prototype._addScrollEventListener=function(a){this._scrollBottom(),this._numMessagesDisplayed=a,e.define(this.messageArea.find(p.MESSAGES),[e.events.scrollTop]),this.messageArea.onCustomEvent(e.events.scrollTop,this._loadMessages.bind(this))},m.prototype._deleteAllMessages=function(){this._confirmationModal?this._confirmationModal.show():j.get_strings([{key:"confirm"},{key:"deleteallconfirm",component:"message"}]).done(function(a){h.create({title:a[0],type:h.types.CONFIRM,body:a[1]},this.messageArea.find(p.DELETEALLMESSAGES)).done(function(a){this._confirmationModal=a,a.getRoot().on(i.yes,function(){var a=this._getUserId(),c={methodname:"core_message_delete_conversation",args:{userid:this.messageArea.getCurrentUserId(),otheruserid:a}};b.call([c])[0].then(function(){this.messageArea.find(p.MESSAGESAREA).empty(),this.messageArea.trigger(k.CONVERSATIONDELETED,a),this._hideDeleteAction()}.bind(this),d.exception)}.bind(this)),a.show()}.bind(this))}.bind(this))},m.prototype._hideDeleteAction=function(){this.messageArea.find(p.MESSAGE).removeAttr("role").removeAttr("aria-checked"),this.messageArea.find(p.MESSAGESAREA).removeClass("editing")},m.prototype._triggerCancelMessagesToDelete=function(){this.messageArea.trigger(k.CANCELDELETEMESSAGES)},m.prototype._addMessageToDom=function(){var a=b.call([{methodname:"core_message_data_for_messagearea_get_most_recent_message",args:{currentuserid:this.messageArea.getCurrentUserId(),otheruserid:this._getUserId()}}]);return a[0].then(function(a){return c.render("core_message/message_area_message",a)}).then(function(a,b){c.appendNodeContents(this.messageArea.find(p.MESSAGES),a,b),this.messageArea.find(p.SENDMESSAGETEXT).val("").trigger("input"),this._scrollBottom()}.bind(this)).fail(d.exception)},m.prototype._getUserId=function(){return this.messageArea.find(p.MESSAGES).data("userid")},m.prototype._scrollBottom=function(){var a=this.messageArea.find(p.MESSAGES);0!==a.length&&a.scrollTop(a[0].scrollHeight)},m.prototype._selectPreviousMessage=function(b,c){var d=a(b.target).closest(p.MESSAGE);do d=d.prev();while(d.length&&!d.is(p.MESSAGE));d.focus(),c.originalEvent.preventDefault(),c.originalEvent.stopPropagation()},m.prototype._selectNextMessage=function(b,c){var d=a(b.target).closest(p.MESSAGE);do d=d.next();while(d.length&&!d.is(p.MESSAGE));d.focus(),c.originalEvent.preventDefault(),c.originalEvent.stopPropagation()},m.prototype._setMessaging=function(b){a(b.target).closest(p.MESSAGERESPONSE).addClass("messaging")},m.prototype._clearMessaging=function(b){a(b.target).closest(p.MESSAGERESPONSE).removeClass("messaging")},m.prototype._startDeleting=function(a){var b=new g(this.messageArea);b.chooseMessagesToDelete(),a.preventDefault()},m.prototype._isEditing=function(){return this.messageArea.find(p.MESSAGESAREA).hasClass("editing")},m.prototype._toggleMessage=function(b){if(this._isEditing()){var c=a(b.target).closest(p.MESSAGE);"true"===c.attr("aria-checked")?c.attr("aria-checked","false"):c.attr("aria-checked","true")}},m.prototype._adjustMessagesAreaHeight=function(){var a=this.messageArea.find(p.MESSAGES),b=this.messageArea.find(p.MESSAGERESPONSE),c=b.outerHeight(),d=c-o,e=n-d;a.outerHeight(e)},m.prototype._sendMessageHandler=function(a,b){b.originalEvent.preventDefault(),this._sendMessage()},m.prototype._hideMessagingArea=function(){this.messageArea.find(p.MESSAGINGAREA).removeClass("show-messages").addClass("hide-messages")},m});
\ No newline at end of file
diff --git a/message/amd/src/message_area_messages.js b/message/amd/src/message_area_messages.js
index 51394caaf3186..a24ef0b0990e2 100644
--- a/message/amd/src/message_area_messages.js
+++ b/message/amd/src/message_area_messages.js
@@ -23,8 +23,9 @@
  */
 define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/custom_interaction_events',
         'core/auto_rows', 'core_message/message_area_actions', 'core/modal_factory', 'core/modal_events',
-        'core/str', 'core_message/message_area_events'],
-    function($, Ajax, Templates, Notification, CustomEvents, AutoRows, Actions, ModalFactory, ModalEvents, Str, Events) {
+        'core/str', 'core_message/message_area_events', 'core/backoff_timer'],
+    function($, Ajax, Templates, Notification, CustomEvents, AutoRows, Actions, ModalFactory,
+             ModalEvents, Str, Events, BackOffTimer) {
 
         /** @type {int} The message area default height. */
         var MESSAGES_AREA_DEFAULT_HEIGHT = 500;
@@ -77,6 +78,12 @@ define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/cust
         /** @type {Modal} the confirmation modal */
         Messages.prototype._confirmationModal = null;
 
+        /** @type {int} the timestamp for the earliest visible message */
+        Messages.prototype._earliestMessageTimestamp = 0;
+
+        /** @type {BackOffTime} the backoff timer */
+        Messages.prototype._timer = null;
+
         /** @type {Messagearea} The messaging area object. */
         Messages.prototype.messageArea = null;
 
@@ -137,6 +144,14 @@ define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/cust
             if (messages.length) {
                 this._addScrollEventListener(messages.find(SELECTORS.MESSAGE).length);
             }
+
+            // Create a timer to poll the server for new messages.
+            this._timer = new BackOffTimer(function() {
+                this._loadNewMessages();
+            }.bind(this));
+
+            // Start the timer.
+            this._timer.start();
         };
 
         /**
@@ -150,6 +165,10 @@ define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/cust
         Messages.prototype._viewMessages = function(event, userid) {
             // We are viewing another user, or re-loading the panel, so set number of messages displayed to 0.
             this._numMessagesDisplayed = 0;
+            // Stop the existing timer so we can set up the new user's messages.
+            this._timer.stop();
+            // Reset the earliest timestamp when we change the messages view.
+            this._earliestMessageTimestamp = 0;
 
             // Mark all the messages as read.
             var markMessagesAsRead = Ajax.call([{
@@ -183,6 +202,8 @@ define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/cust
             }).then(function(html, js) {
                 Templates.replaceNodeContents(this.messageArea.find(SELECTORS.MESSAGESAREA), html, js);
                 this._addScrollEventListener(numberreceived);
+                // Restart the poll timer.
+                this._timer.restart();
             }.bind(this)).fail(Notification.exception);
         };
 
@@ -240,28 +261,130 @@ define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/cust
             }.bind(this)).fail(Notification.exception);
         };
 
+        /**
+         * Loads and renders messages newer than the most recently seen messages.
+         *
+         * @return {Promise|boolean} The promise resolved when the messages have been loaded.
+         * @private
+         */
+        Messages.prototype._loadNewMessages = function() {
+            if (this._isLoadingMessages) {
+                return false;
+            }
+
+            // If we have no user id yet then bail early.
+            if (!this._getUserId()) {
+                return false;
+            }
+
+            this._isLoadingMessages = true;
+
+            // Only scroll the message window if the user hasn't scrolled up.
+            var shouldScrollBottom = false;
+            var messages = this.messageArea.find(SELECTORS.MESSAGES);
+            if (messages.length !== 0) {
+                var scrollTop = messages.scrollTop();
+                var innerHeight = messages.innerHeight();
+                var scrollHeight = messages[0].scrollHeight;
+
+                if (scrollTop + innerHeight >= scrollHeight) {
+                    shouldScrollBottom = true;
+                }
+            }
+
+            // Keep track of the number of messages received.
+            var numberreceived = 0;
+            return this._getMessages(this._getUserId(), true).then(function(data) {
+                // Filter out any messages already rendered.
+                var messagesArea = this.messageArea.find(SELECTORS.MESSAGES);
+                data.messages = data.messages.filter(function(message) {
+                    var id = "" + message.id + message.isread;
+                    var result = messagesArea.find(SELECTORS.MESSAGE + '[data-id="' + id + '"]');
+                    return !result.length;
+                });
+
+                numberreceived = data.messages.length;
+                // We have the data - lets render the template with it.
+                return Templates.render('core_message/message_area_messages', data);
+            }.bind(this)).then(function(html, js) {
+                // Check if we got something to do.
+                if (numberreceived > 0) {
+                    html = $(html);
+                    // Remove the new block time as it's present above.
+                    html.find(SELECTORS.BLOCKTIME).remove();
+                    // Show the new content.
+                    Templates.appendNodeContents(this.messageArea.find(SELECTORS.MESSAGES), html, js);
+                    // Scroll the new message into view.
+                    if (shouldScrollBottom) {
+                        this._scrollBottom();
+                    }
+                    // Increment the number of messages displayed.
+                    this._numMessagesDisplayed += numberreceived;
+                    // Reset the poll timer because the user may be active.
+                    this._timer.restart();
+                }
+            }.bind(this)).always(function() {
+                // Mark that we are no longer busy loading data.
+                this._isLoadingMessages = false;
+            }.bind(this)).fail(Notification.exception);
+        };
+
         /**
          * Handles returning a list of messages to display.
          *
          * @param {int} userid
+         * @param {bool} fromTimestamp Load messages from the earliest known timestamp
          * @return {Promise} The promise resolved when the contact area has been rendered
          * @private
          */
-        Messages.prototype._getMessages = function(userid) {
+        Messages.prototype._getMessages = function(userid, fromTimestamp) {
+            var args = {
+                currentuserid: this.messageArea.getCurrentUserId(),
+                otheruserid: userid,
+                limitfrom: this._numMessagesDisplayed,
+                limitnum: this._numMessagesToRetrieve,
+                newest: true
+            };
+
+            // If we're trying to load new messages since the message UI was
+            // rendered. Used for ajax polling while user is on the message UI.
+            if (fromTimestamp) {
+                args.createdfrom = this._earliestMessageTimestamp;
+                // Remove limit and offset. We want all new messages.
+                args.limitfrom = 0;
+                args.limitnum = 0;
+            }
+
             // Call the web service to get our data.
             var promises = Ajax.call([{
                 methodname: 'core_message_data_for_messagearea_messages',
-                args: {
-                    currentuserid: this.messageArea.getCurrentUserId(),
-                    otheruserid: userid,
-                    limitfrom: this._numMessagesDisplayed,
-                    limitnum: this._numMessagesToRetrieve,
-                    newest: true
-                }
+                args: args,
             }]);
 
             // Do stuff when we get data back.
-            return promises[0];
+            return promises[0].then(function(data) {
+                var messages = data.messages;
+
+                // Did we get any new messages?
+                if (messages && messages.length) {
+                    var earliestMessage = messages[messages.length - 1];
+
+                    // If we haven't set the timestamp yet then just use the earliest message.
+                    if (!this._earliestMessageTimestamp) {
+                        // Next request should be for the second after the most recent message we've seen.
+                        this._earliestMessageTimestamp = earliestMessage.timecreated + 1;
+                    // Update our record of the earliest known message for future requests.
+                    } else if (earliestMessage.timecreated < this._earliestMessageTimestamp) {
+                        // Next request should be for the second after the most recent message we've seen.
+                        this._earliestMessageTimestamp = earliestMessage.timecreated + 1;
+                    }
+                }
+
+                return data;
+            }.bind(this)).fail(function() {
+                // Stop the timer if we received an error so that we don't keep spamming the server.
+                this._timer.stop();
+            }.bind(this)).fail(Notification.exception);
         };
 
         /**
diff --git a/message/classes/api.php b/message/classes/api.php
index eabe7d7379b0c..2d6150f03862f 100644
--- a/message/classes/api.php
+++ b/message/classes/api.php
@@ -291,11 +291,32 @@ public static function get_contacts($userid, $limitfrom = 0, $limitnum = 0) {
      * @param int $limitfrom
      * @param int $limitnum
      * @param string $sort
+     * @param int $createdfrom the timestamp from which the messages were created
+     * @param int $createdto the time up until which the message was created
      * @return array
      */
-    public static function get_messages($userid, $otheruserid, $limitfrom = 0, $limitnum = 0, $sort = 'timecreated ASC') {
+    public static function get_messages($userid, $otheruserid, $limitfrom = 0, $limitnum = 0,
+        $sort = 'timecreated ASC', $createdfrom = 0, $createdto = 0) {
+
+        if (!empty($createdfrom)) {
+            // Check the cache to see if we even need to do a DB query.
+            $cache = \cache::make('core', 'message_last_created');
+            $ids = [$otheruserid, $userid];
+            sort($ids);
+            $key = implode('_', $ids);
+            $lastcreated = $cache->get($key);
+
+            // The last known message time is earlier than the one being requested so we can
+            // just return an empty result set rather than having to query the DB.
+            if ($lastcreated && $lastcreated < $createdfrom) {
+                return [];
+            }
+        }
+
         $arrmessages = array();
-        if ($messages = helper::get_messages($userid, $otheruserid, 0, $limitfrom, $limitnum, $sort)) {
+        if ($messages = helper::get_messages($userid, $otheruserid, 0, $limitfrom, $limitnum,
+                                             $sort, $createdfrom, $createdto)) {
+
             $arrmessages = helper::create_messages($userid, $messages);
         }
 
diff --git a/message/classes/helper.php b/message/classes/helper.php
index 4fe71226aa9ab..3a4c70d730d10 100644
--- a/message/classes/helper.php
+++ b/message/classes/helper.php
@@ -43,10 +43,12 @@ class helper {
      * @param int $limitfrom
      * @param int $limitnum
      * @param string $sort
+     * @param int $createdfrom the time from which the message was created
+     * @param int $createdto the time up until which the message was created
      * @return array of messages
      */
     public static function get_messages($userid, $otheruserid, $timedeleted = 0, $limitfrom = 0, $limitnum = 0,
-                                        $sort = 'timecreated ASC') {
+                                        $sort = 'timecreated ASC', $createdfrom = 0, $createdto = 0) {
         global $DB;
 
         $messageid = $DB->sql_concat("'message_'", 'id');
@@ -58,6 +60,7 @@ public static function get_messages($userid, $otheruserid, $timedeleted = 0, $li
                  WHERE ((useridto = ? AND useridfrom = ? AND timeusertodeleted = ?)
                     OR (useridto = ? AND useridfrom = ? AND timeuserfromdeleted = ?))
                    AND notification = 0
+                   %where%
              UNION ALL
                 SELECT {$messagereadid} AS fakeid, id, useridfrom, useridto, subject, fullmessage, fullmessagehtml, fullmessageformat,
                        smallmessage, notification, timecreated, timeread
@@ -65,11 +68,29 @@ public static function get_messages($userid, $otheruserid, $timedeleted = 0, $li
                  WHERE ((useridto = ? AND useridfrom = ? AND timeusertodeleted = ?)
                     OR (useridto = ? AND useridfrom = ? AND timeuserfromdeleted = ?))
                    AND notification = 0
+                   %where%
               ORDER BY $sort";
-        $params = array($userid, $otheruserid, $timedeleted,
-                        $otheruserid, $userid, $timedeleted,
-                        $userid, $otheruserid, $timedeleted,
-                        $otheruserid, $userid, $timedeleted);
+        $params1 = array($userid, $otheruserid, $timedeleted,
+                         $otheruserid, $userid, $timedeleted);
+
+        $params2 = array($userid, $otheruserid, $timedeleted,
+                         $otheruserid, $userid, $timedeleted);
+        $where = array();
+
+        if (!empty($createdfrom)) {
+            $where[] = 'AND timecreated >= ?';
+            $params1[] = $createdfrom;
+            $params2[] = $createdfrom;
+        }
+
+        if (!empty($createdto)) {
+            $where[] = 'AND timecreated <= ?';
+            $params1[] = $createdto;
+            $params2[] = $createdto;
+        }
+
+        $sql = str_replace('%where%', implode(' ', $where), $sql);
+        $params = array_merge($params1, $params2);
 
         return $DB->get_records_sql($sql, $params, $limitfrom, $limitnum);
     }
diff --git a/message/classes/message_last_created_cache_source.php b/message/classes/message_last_created_cache_source.php
new file mode 100644
index 0000000000000..ea0cd05df1b12
--- /dev/null
+++ b/message/classes/message_last_created_cache_source.php
@@ -0,0 +1,89 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Cache data source for the last created message between users.
+ *
+ * @package    core_message
+ * @category   cache
+ * @copyright  2016 Ryan Wyllie <ryan@moodle.com>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Cache data source for the last created message between users.
+ *
+ * @package    core_message
+ * @category   cache
+ * @copyright  2016 Ryan Wyllie <ryan@moodle.com>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class message_last_created_cache_source implements \cache_data_source {
+
+    /** @var message_last_created_cache_source the singleton instance of this class. */
+    protected static $instance = null;
+
+    /**
+     * Returns an instance of the data source class that the cache can use for loading data using the other methods
+     * specified by the cache_data_source interface.
+     *
+     * @param cache_definition $definition
+     * @return object
+     */
+    public static function get_instance_for_cache(cache_definition $definition) {
+        if (is_null(self::$instance)) {
+            self::$instance = new message_last_created_cache_source();
+        }
+        return self::$instance;
+    }
+
+    /**
+     * Loads the data for the key provided ready formatted for caching.
+     *
+     * @param string|int $key The key to load.
+     * @return mixed What ever data should be returned, or false if it can't be loaded.
+     */
+    public function load_for_cache($key) {
+        list($userid1, $userid2) = explode('_', $key);
+
+        $message = \core_message\api::get_most_recent_message($userid1, $userid2);
+
+        if ($message) {
+            return $message->timecreated;
+        } else {
+            return null;
+        }
+    }
+
+    /**
+     * Loads several keys for the cache.
+     *
+     * @param array $keys An array of keys each of which will be string|int.
+     * @return array An array of matching data items.
+     */
+    public function load_many_for_cache(array $keys) {
+        $results = [];
+
+        foreach ($keys as $key) {
+            $results[] = $this->load_for_cache($key);
+        }
+
+        return $results;
+    }
+}
diff --git a/message/classes/output/messagearea/message.php b/message/classes/output/messagearea/message.php
index 00813498ca449..5fc7e0579d915 100644
--- a/message/classes/output/messagearea/message.php
+++ b/message/classes/output/messagearea/message.php
@@ -107,6 +107,7 @@ public function export_for_template(\renderer_base $output) {
             $message->position = 'right';
         }
         $message->timesent = userdate($this->timecreated, get_string('strftimetime'));
+        $message->timecreated = $this->timecreated;
         $message->isread = !empty($this->timeread) ? 1 : 0;
 
         return $message;
diff --git a/message/externallib.php b/message/externallib.php
index 2ecaf66b101b2..98b5634c9d6c7 100644
--- a/message/externallib.php
+++ b/message/externallib.php
@@ -515,6 +515,7 @@ private static function get_messagearea_message_structure() {
                 'blocktime' => new external_value(PARAM_NOTAGS, 'The time to display above the message'),
                 'position' => new external_value(PARAM_ALPHA, 'The position of the text'),
                 'timesent' => new external_value(PARAM_NOTAGS, 'The time the message was sent'),
+                'timecreated' => new external_value(PARAM_INT, 'The timecreated timestamp for the message'),
                 'isread' => new external_value(PARAM_INT, 'Determines if the message was read or not'),
             )
         );
@@ -900,6 +901,8 @@ public static function data_for_messagearea_messages_parameters() {
                 'limitfrom' => new external_value(PARAM_INT, 'Limit from', VALUE_DEFAULT, 0),
                 'limitnum' => new external_value(PARAM_INT, 'Limit number', VALUE_DEFAULT, 0),
                 'newest' => new external_value(PARAM_BOOL, 'Newest first?', VALUE_DEFAULT, false),
+                'createdfrom' => new external_value(PARAM_INT,
+                    'The timestamp from which the messages were created', VALUE_DEFAULT, 0),
             )
         );
     }
@@ -917,7 +920,7 @@ public static function data_for_messagearea_messages_parameters() {
      * @since 3.2
      */
     public static function data_for_messagearea_messages($currentuserid, $otheruserid, $limitfrom = 0, $limitnum = 0,
-                                                         $newest = false) {
+                                                         $newest = false, $createdfrom = 0) {
         global $CFG, $PAGE, $USER;
 
         // Check if messaging is enabled.
@@ -932,7 +935,8 @@ public static function data_for_messagearea_messages($currentuserid, $otheruseri
             'otheruserid' => $otheruserid,
             'limitfrom' => $limitfrom,
             'limitnum' => $limitnum,
-            'newest' => $newest
+            'newest' => $newest,
+            'createdfrom' => $createdfrom,
         );
         self::validate_parameters(self::data_for_messagearea_messages_parameters(), $params);
         self::validate_context($systemcontext);
@@ -946,7 +950,29 @@ public static function data_for_messagearea_messages($currentuserid, $otheruseri
         } else {
             $sort = 'timecreated ASC';
         }
-        $messages = \core_message\api::get_messages($currentuserid, $otheruserid, $limitfrom, $limitnum, $sort);
+
+        // We need to enforce a one second delay on messages to avoid race conditions of current
+        // messages still being sent.
+        //
+        // There is a chance that we could request messages before the current time's
+        // second has elapsed and while other messages are being sent in that same second. In which
+        // case those messages will be lost.
+        //
+        // Instead we ignore the current time in the result set to ensure that second is allowed to finish.
+        if (!empty($createdfrom)) {
+            $createdto = time() - 1;
+        } else {
+            $createdto = 0;
+        }
+
+        // No requesting messages from the current time, as stated above.
+        if ($createdfrom == time()) {
+            $mesages = [];
+        } else {
+            $messages = \core_message\api::get_messages($currentuserid, $otheruserid, $limitfrom,
+                                                        $limitnum, $sort, $createdfrom, $createdto);
+        }
+
         $messages = new \core_message\output\messagearea\messages($currentuserid, $otheruserid, $messages);
 
         $renderer = $PAGE->get_renderer('core_message');
diff --git a/message/tests/api_test.php b/message/tests/api_test.php
index 67d898ed56900..15376e049370d 100644
--- a/message/tests/api_test.php
+++ b/message/tests/api_test.php
@@ -953,4 +953,129 @@ public function is_user_enabled() {
         $status = \core_message\api::is_processor_enabled($name);
         $this->assertEquals(1, $status);
     }
+
+    /**
+     * Test retrieving messages by providing a minimum timecreated value.
+     */
+    public function test_get_messages_created_from_only() {
+        // Create some users.
+        $user1 = self::getDataGenerator()->create_user();
+        $user2 = self::getDataGenerator()->create_user();
+
+        // The person doing the search.
+        $this->setUser($user1);
+
+        // Send some messages back and forth.
+        $time = 1;
+        $this->send_fake_message($user1, $user2, 'Message 1', 0, $time + 1);
+        $this->send_fake_message($user2, $user1, 'Message 2', 0, $time + 2);
+        $this->send_fake_message($user1, $user2, 'Message 3', 0, $time + 3);
+        $this->send_fake_message($user2, $user1, 'Message 4', 0, $time + 4);
+
+        // Retrieve the messages.
+        $messages = \core_message\api::get_messages($user1->id, $user2->id, 0, 0, 'timecreated ASC', $time);
+
+        // Confirm the message data is correct.
+        $this->assertEquals(4, count($messages));
+
+        $message1 = $messages[0];
+        $message2 = $messages[1];
+        $message3 = $messages[2];
+        $message4 = $messages[3];
+
+        $this->assertContains('Message 1', $message1->text);
+        $this->assertContains('Message 2', $message2->text);
+        $this->assertContains('Message 3', $message3->text);
+        $this->assertContains('Message 4', $message4->text);
+
+        // Retrieve the messages.
+        $messages = \core_message\api::get_messages($user1->id, $user2->id, 0, 0, 'timecreated ASC', $time + 3);
+
+        // Confirm the message data is correct.
+        $this->assertEquals(2, count($messages));
+
+        $message1 = $messages[0];
+        $message2 = $messages[1];
+
+        $this->assertContains('Message 3', $message1->text);
+        $this->assertContains('Message 4', $message2->text);
+    }
+
+    /**
+     * Test retrieving messages by providing a maximum timecreated value.
+     */
+    public function test_get_messages_created_to_only() {
+        // Create some users.
+        $user1 = self::getDataGenerator()->create_user();
+        $user2 = self::getDataGenerator()->create_user();
+
+        // The person doing the search.
+        $this->setUser($user1);
+
+        // Send some messages back and forth.
+        $time = 1;
+        $this->send_fake_message($user1, $user2, 'Message 1', 0, $time + 1);
+        $this->send_fake_message($user2, $user1, 'Message 2', 0, $time + 2);
+        $this->send_fake_message($user1, $user2, 'Message 3', 0, $time + 3);
+        $this->send_fake_message($user2, $user1, 'Message 4', 0, $time + 4);
+
+        // Retrieve the messages.
+        $messages = \core_message\api::get_messages($user1->id, $user2->id, 0, 0, 'timecreated ASC', 0, $time + 4);
+
+        // Confirm the message data is correct.
+        $this->assertEquals(4, count($messages));
+
+        $message1 = $messages[0];
+        $message2 = $messages[1];
+        $message3 = $messages[2];
+        $message4 = $messages[3];
+
+        $this->assertContains('Message 1', $message1->text);
+        $this->assertContains('Message 2', $message2->text);
+        $this->assertContains('Message 3', $message3->text);
+        $this->assertContains('Message 4', $message4->text);
+
+        // Retrieve the messages.
+        $messages = \core_message\api::get_messages($user1->id, $user2->id, 0, 0, 'timecreated ASC', 0, $time + 2);
+
+        // Confirm the message data is correct.
+        $this->assertEquals(2, count($messages));
+
+        $message1 = $messages[0];
+        $message2 = $messages[1];
+
+        $this->assertContains('Message 1', $message1->text);
+        $this->assertContains('Message 2', $message2->text);
+    }
+
+    /**
+     * Test retrieving messages by providing a minimum and maximum timecreated value.
+     */
+    public function test_get_messages_created_from_and_to() {
+        // Create some users.
+        $user1 = self::getDataGenerator()->create_user();
+        $user2 = self::getDataGenerator()->create_user();
+
+        // The person doing the search.
+        $this->setUser($user1);
+
+        // Send some messages back and forth.
+        $time = 1;
+        $this->send_fake_message($user1, $user2, 'Message 1', 0, $time + 1);
+        $this->send_fake_message($user2, $user1, 'Message 2', 0, $time + 2);
+        $this->send_fake_message($user1, $user2, 'Message 3', 0, $time + 3);
+        $this->send_fake_message($user2, $user1, 'Message 4', 0, $time + 4);
+
+        // Retrieve the messages.
+        $messages = \core_message\api::get_messages($user1->id, $user2->id, 0, 0, 'timecreated ASC', $time + 2, $time + 3);
+
+        // Confirm the message data is correct.
+        $this->assertEquals(2, count($messages));
+
+        $message1 = $messages[0];
+        $message2 = $messages[1];
+
+        $this->assertContains('Message 2', $message1->text);
+        $this->assertContains('Message 3', $message2->text);
+    }
 }
diff --git a/message/tests/externallib_test.php b/message/tests/externallib_test.php
index f28c50e7d036d..c739b1a4e3664 100644
--- a/message/tests/externallib_test.php
+++ b/message/tests/externallib_test.php
@@ -1979,6 +1979,46 @@ public function test_messagearea_messages() {
         $this->assertContains('Word.', $message4['text']);
     }
 
+    /**
+     * Tests retrieving messages.
+     */
+    public function test_messagearea_messages_createfrom() {
+        $this->resetAfterTest(true);
+
+        // Create some users.
+        $user1 = self::getDataGenerator()->create_user();
+        $user2 = self::getDataGenerator()->create_user();
+
+        // The person asking for the messages.
+        $this->setUser($user1);
+
+        // Send some messages back and forth.
+        $time = time();
+        $this->send_message($user1, $user2, 'Message 1', 0, $time - 4);
+        $this->send_message($user2, $user1, 'Message 2', 0, $time - 3);
+        $this->send_message($user1, $user2, 'Message 3', 0, $time - 2);
+        $this->send_message($user2, $user1, 'Message 4', 0, $time - 1);
+
+        // Retrieve the messages.
+        $result = core_message_external::data_for_messagearea_messages($user1->id, $user2->id, 0, 0, false, $time - 3);
+
+        // We need to execute the return values cleaning process to simulate the web service server.
+        $result = external_api::clean_returnvalue(core_message_external::data_for_messagearea_messages_returns(),
+            $result);
+
+        // Confirm the message data is correct. We shouldn't get 'Message 1' back.
+        $messages = $result['messages'];
+        $this->assertCount(3, $messages);
+
+        $message1 = $messages[0];
+        $message2 = $messages[1];
+        $message3 = $messages[2];
+
+        $this->assertContains('Message 2', $message1['text']);
+        $this->assertContains('Message 3', $message2['text']);
+        $this->assertContains('Message 4', $message3['text']);
+    }
+
     /**
      * Tests retrieving messages as another user.
      */
diff --git a/version.php b/version.php
index e49f805713dd1..e23de8f66c731 100644
--- a/version.php
+++ b/version.php
@@ -29,11 +29,11 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$version  = 2016111500.00;              // YYYYMMDD      = weekly release date of this DEV branch.
+$version  = 2016111600.00;              // YYYYMMDD      = weekly release date of this DEV branch.
                                         //         RR    = release increments - 00 in DEV branches.
                                         //           .XX = incremental changes.
 
-$release  = '3.2beta+ (Build: 20161115)'; // Human-friendly version name
+$release  = '3.2beta+ (Build: 20161116)'; // Human-friendly version name
 
 $branch   = '32';                       // This version's branch.
 $maturity = MATURITY_BETA;             // This version's maturity level.

From ffd7798c960bc4f26d51b806f95a4877844ddd74 Mon Sep 17 00:00:00 2001
From: Mark Nelson <markn@moodle.com>
Date: Thu, 10 Nov 2016 12:47:20 +0800
Subject: [PATCH 2/3] MDL-56139 core: changes after peer review

- No longer use the Fibonacci sequence for delaying the timeout.
  It is too aggressive.
- The backoff_timer AMD module now expects the callback AND the
  backoff function to be passed to the constructor.
- Added ability to specify polling frequency in config.php.
- Added helper function to return the cache key.
- Reworded the parameters for clarity.
---
 lang/en/cache.php                             |   2 +-
 lib/amd/build/backoff_timer.min.js            |   2 +-
 lib/amd/src/backoff_timer.js                  | 133 +++++++-----------
 lib/db/caches.php                             |   7 +-
 lib/messagelib.php                            |   7 +-
 message/amd/build/message_area.min.js         |   2 +-
 .../amd/build/message_area_messages.min.js    |   2 +-
 message/amd/src/message_area.js               |  17 ++-
 message/amd/src/message_area_messages.js      |  30 ++--
 message/classes/api.php                       |  18 ++-
 message/classes/helper.php                    |  31 ++--
 .../output/messagearea/message_area.php       |  27 +++-
 ...hp => time_last_message_between_users.php} |  17 +--
 message/externallib.php                       |  18 +--
 message/index.php                             |   5 +-
 message/lib.php                               |   7 +
 message/templates/message_area.mustache       |   2 +-
 message/tests/api_test.php                    |  16 +--
 message/tests/externallib_test.php            |   4 +-
 19 files changed, 190 insertions(+), 157 deletions(-)
 rename message/classes/{message_last_created_cache_source.php => time_last_message_between_users.php} (79%)

diff --git a/lang/en/cache.php b/lang/en/cache.php
index ae490cbaadb1e..b97ae2b189e70 100644
--- a/lang/en/cache.php
+++ b/lang/en/cache.php
@@ -52,7 +52,7 @@
 $string['cachedef_groupdata'] = 'Course group information';
 $string['cachedef_htmlpurifier'] = 'HTML Purifier - cleaned content';
 $string['cachedef_langmenu'] = 'List of available languages';
-$string['cachedef_message_last_created'] = 'Time created for most recent message between users';
+$string['cachedef_message_time_last_message_between_users'] = 'Time created for most recent message between users';
 $string['cachedef_locking'] = 'Locking';
 $string['cachedef_message_processors_enabled'] = "Message processors enabled status";
 $string['cachedef_navigation_expandcourse'] = 'Navigation expandable courses';
diff --git a/lib/amd/build/backoff_timer.min.js b/lib/amd/build/backoff_timer.min.js
index b1d81162ea102..bb80b45d1235f 100644
--- a/lib/amd/build/backoff_timer.min.js
+++ b/lib/amd/build/backoff_timer.min.js
@@ -1 +1 @@
-define(function(){var a=1e3,b=function(b,c){if(!b)return a;if(c.length){var d=c[c.length-1];return b+d}return a},c=function(a){this.reset(),this.setCallback(a),this.setBackOffFunction(b)};return c.prototype.setCallback=function(a){return this.callback=a,this},c.prototype.getCallback=function(){return this.callback},c.prototype.setBackOffFunction=function(a){return this.backOffFunction=a,this},c.prototype.getBackOffFunction=function(){return this.backOffFunction},c.prototype.generateNextTime=function(){var a=this.getBackOffFunction().call(this.getBackOffFunction(),this.time,this.previousTimes);return this.previousTimes.push(this.time),this.time=a,a},c.prototype.reset=function(){return this.time=null,this.previousTimes=[],this.stop(),this},c.prototype.stop=function(){return this.timeout&&(window.clearTimeout(this.timeout),this.timeout=null),this},c.prototype.start=function(){if(!this.timeout){var a=this.generateNextTime();this.timeout=window.setTimeout(function(){this.getCallback().call(),this.stop(),this.start()}.bind(this),a)}return this},c.prototype.restart=function(){return this.reset().start()},c});
\ No newline at end of file
+define(function(){var a=function(a,b){this.callback=a,this.backOffFunction=b};return a.prototype.callback=null,a.prototype.backOffFunction=null,a.prototype.time=null,a.prototype.timeout=null,a.prototype.generateNextTime=function(){var a=this.backOffFunction(this.time);return this.time=a,a},a.prototype.reset=function(){return this.time=null,this.stop(),this},a.prototype.stop=function(){return this.timeout&&(window.clearTimeout(this.timeout),this.timeout=null),this},a.prototype.start=function(){if(!this.timeout){var a=this.generateNextTime();this.timeout=window.setTimeout(function(){this.callback(),this.stop(),this.start()}.bind(this),a)}return this},a.prototype.restart=function(){return this.reset().start()},a.getIncrementalCallback=function(a,b,c,d){return function(e){return e?e+b>c?d:e+b:a}},a});
\ No newline at end of file
diff --git a/lib/amd/src/backoff_timer.js b/lib/amd/src/backoff_timer.js
index 992a322d70660..da0fabdb0861d 100644
--- a/lib/amd/src/backoff_timer.js
+++ b/lib/amd/src/backoff_timer.js
@@ -25,92 +25,36 @@
  */
 define(function() {
 
-    // Default to one second.
-    var DEFAULT_TIME = 1000;
-
-    /**
-     * The default back off function for the timer. It uses the Fibonacci
-     * sequence to determine what the next timeout value should be.
-     *
-     * @param {(int|null)} time The current timeout value or null if none set
-     * @param {array} previousTimes An array containing all previous timeout values
-     * @return {int} The new timeout value
-     */
-    var fibonacciBackOff = function(time, previousTimes) {
-        if (!time) {
-            return DEFAULT_TIME;
-        }
-
-        if (previousTimes.length) {
-            var lastTime = previousTimes[previousTimes.length - 1];
-            return time + lastTime;
-        } else {
-            return DEFAULT_TIME;
-        }
-    };
-
     /**
      * Constructor for the back off timer.
      *
      * @param {function} callback The function to execute after each tick
+     * @param {function} backoffFunction The function to determine what the next timeout value should be
      */
-    var Timer = function(callback) {
-        this.reset();
-        this.setCallback(callback);
-        // Set the default backoff function to be the Fibonacci sequence.
-        this.setBackOffFunction(fibonacciBackOff);
+    var BackoffTimer = function(callback, backoffFunction) {
+        this.callback = callback;
+        this.backOffFunction = backoffFunction;
     };
 
     /**
-     * Set the callback function to be executed after each tick of the
-     * timer.
-     *
-     * @method setCallback
-     * @param {function} callback The callback function
-     * @return {object} this
+     * @type {function} callback The function to execute after each tick
      */
-    Timer.prototype.setCallback = function(callback) {
-        this.callback = callback;
-
-        return this;
-    };
+    BackoffTimer.prototype.callback = null;
 
     /**
-     * Get the callback function for this timer.
-     *
-     * @method getCallback
-     * @return {function}
+     * @type {function} backoffFunction The function to determine what the next timeout value should be
      */
-    Timer.prototype.getCallback = function() {
-        return this.callback;
-    };
+    BackoffTimer.prototype.backOffFunction = null;
 
     /**
-     * Set the function to be used when calculating the back off time
-     * for each tick of the timer.
-     *
-     * The back off function will be given two parameters: the current
-     * time and an array containing all previous times.
-     *
-     * @method setBackOffFunction
-     * @param {function} backOffFunction The function to calculate back off times
-     * @return {object} this
+     * @type {int} time The timeout value to use
      */
-    Timer.prototype.setBackOffFunction = function(backOffFunction) {
-        this.backOffFunction = backOffFunction;
-
-        return this;
-    };
+    BackoffTimer.prototype.time = null;
 
     /**
-     * Get the current back off function.
-     *
-     * @method getBackOffFunction
-     * @return {function}
+     * @type {numeric} timeout The timeout identifier
      */
-    Timer.prototype.getBackOffFunction = function() {
-        return this.backOffFunction;
-    };
+    BackoffTimer.prototype.timeout = null;
 
     /**
      * Generate the next timeout in the back off time sequence
@@ -122,13 +66,8 @@ define(function() {
      * @method generateNextTime
      * @return {int} The new timeout value (in milliseconds)
      */
-    Timer.prototype.generateNextTime = function() {
-        var newTime = this.getBackOffFunction().call(
-            this.getBackOffFunction(),
-            this.time,
-            this.previousTimes
-        );
-        this.previousTimes.push(this.time);
+    BackoffTimer.prototype.generateNextTime = function() {
+        var newTime = this.backOffFunction(this.time);
         this.time = newTime;
 
         return newTime;
@@ -140,9 +79,8 @@ define(function() {
      * @method reset
      * @return {object} this
      */
-    Timer.prototype.reset = function() {
+    BackoffTimer.prototype.reset = function() {
         this.time = null;
-        this.previousTimes = [];
         this.stop();
 
         return this;
@@ -154,7 +92,7 @@ define(function() {
      * @method stop
      * @return {object} this
      */
-    Timer.prototype.stop = function() {
+    BackoffTimer.prototype.stop = function() {
         if (this.timeout) {
             window.clearTimeout(this.timeout);
             this.timeout = null;
@@ -175,12 +113,12 @@ define(function() {
      * @method start
      * @return {object} this
      */
-    Timer.prototype.start = function() {
+    BackoffTimer.prototype.start = function() {
         // If we haven't already started.
         if (!this.timeout) {
             var time = this.generateNextTime();
             this.timeout = window.setTimeout(function() {
-                this.getCallback().call();
+                this.callback();
                 // Clear the existing timer.
                 this.stop();
                 // Start the next timer.
@@ -198,9 +136,40 @@ define(function() {
      * @method restart
      * @return {object} this
      */
-    Timer.prototype.restart = function() {
+    BackoffTimer.prototype.restart = function() {
         return this.reset().start();
     };
 
-    return Timer;
+    /**
+     * Returns an incremental function for the timer.
+     *
+     * @param {int} minamount The minimum amount of time we wait before checking
+     * @param {int} incrementamount The amount to increment the timer by
+     * @param {int} maxamount The max amount to ever increment to
+     * @param {int} timeoutamount The timeout to use once we reach the max amount
+     * @return {function}
+     */
+     BackoffTimer.getIncrementalCallback = function(minamount, incrementamount, maxamount, timeoutamount) {
+
+        /**
+         * An incremental function for the timer.
+         *
+         * @param {(int|null)} time The current timeout value or null if none set
+         * @return {int} The new timeout value
+         */
+        return function(time) {
+            if (!time) {
+                return minamount;
+            }
+
+            // Don't go over the max amount.
+            if (time + incrementamount > maxamount) {
+                return timeoutamount;
+            }
+
+            return time + incrementamount;
+        };
+    };
+
+    return BackoffTimer;
 });
diff --git a/lib/db/caches.php b/lib/db/caches.php
index 49e509a818654..9a8e9f24e5d31 100644
--- a/lib/db/caches.php
+++ b/lib/db/caches.php
@@ -302,12 +302,11 @@
         'staticaccelerationsize' => 3
     ),
 
-    // Cache for storing the user's last received message time.
-    'message_last_created' => array(
+    // Caches the time of the last message between two users.
+    'message_time_last_message_between_users' => array(
         'mode' => cache_store::MODE_APPLICATION,
         'simplekeys' => true, // The id of the sender and recipient is used.
         'simplevalues' => true,
-        'datasource' => 'message_last_created_cache_source',
-        'datasourcefile' => 'message/classes/message_last_created_cache_source.php'
+        'datasource' => '\core_message\time_last_message_between_users',
     ),
 );
diff --git a/lib/messagelib.php b/lib/messagelib.php
index 9bfad534db6f4..5347f173b6116 100644
--- a/lib/messagelib.php
+++ b/lib/messagelib.php
@@ -237,10 +237,9 @@ function message_send($eventdata) {
     // Only cache messages, not notifications.
     if (empty($savemessage->notification)) {
         // Cache the timecreated value of the last message between these two users.
-        $cache = cache::make('core', 'message_last_created');
-        $ids = [$savemessage->useridfrom, $savemessage->useridto];
-        sort($ids);
-        $key = implode('_', $ids);
+        $cache = cache::make('core', 'message_time_last_message_between_users');
+        $key = \core_message\helper::get_last_message_time_created_cache_key($savemessage->useridfrom,
+            $savemessage->useridto);
         $cache->set($key, $savemessage->timecreated);
     }
 
diff --git a/message/amd/build/message_area.min.js b/message/amd/build/message_area.min.js
index 942dc1cb22d1b..b117ee3e361f1 100644
--- a/message/amd/build/message_area.min.js
+++ b/message/amd/build/message_area.min.js
@@ -1 +1 @@
-define(["jquery","core_message/message_area_contacts","core_message/message_area_messages","core_message/message_area_profile","core_message/message_area_tabs","core_message/message_area_search"],function(a,b,c,d,e,f){function g(b){this.node=a(b),this._init()}return g.prototype.node=null,g.prototype._init=function(){new b(this),new c(this),new d(this),new e(this),new f(this)},g.prototype.onDelegateEvent=function(a,b,c){this.node.on(a,b,c)},g.prototype.onCustomEvent=function(a,b){this.node.on(a,b)},g.prototype.trigger=function(a,b){"undefined"==typeof b&&(b=""),this.node.trigger(a,b)},g.prototype.find=function(a){return this.node.find(a)},g.prototype.getCurrentUserId=function(){return this.node.data("userid")},g});
\ No newline at end of file
+define(["jquery","core_message/message_area_contacts","core_message/message_area_messages","core_message/message_area_profile","core_message/message_area_tabs","core_message/message_area_search"],function(a,b,c,d,e,f){function g(b,c,d,e){this.node=a(b),this.pollmin=c,this.pollmax=d,this.polltimeout=e,this._init()}return g.prototype.node=null,g.prototype.pollmin=null,g.prototype.pollmax=null,g.prototype.polltimeout=null,g.prototype._init=function(){new b(this),new c(this),new d(this),new e(this),new f(this)},g.prototype.onDelegateEvent=function(a,b,c){this.node.on(a,b,c)},g.prototype.onCustomEvent=function(a,b){this.node.on(a,b)},g.prototype.trigger=function(a,b){"undefined"==typeof b&&(b=""),this.node.trigger(a,b)},g.prototype.find=function(a){return this.node.find(a)},g.prototype.getCurrentUserId=function(){return this.node.data("userid")},g});
\ No newline at end of file
diff --git a/message/amd/build/message_area_messages.min.js b/message/amd/build/message_area_messages.min.js
index 4ba61b0677a40..09a54373a3f2e 100644
--- a/message/amd/build/message_area_messages.min.js
+++ b/message/amd/build/message_area_messages.min.js
@@ -1 +1 @@
-define(["jquery","core/ajax","core/templates","core/notification","core/custom_interaction_events","core/auto_rows","core_message/message_area_actions","core/modal_factory","core/modal_events","core/str","core_message/message_area_events","core/backoff_timer"],function(a,b,c,d,e,f,g,h,i,j,k,l){function m(a){this.messageArea=a,this._init()}var n=500,o=50,p={BLOCKTIME:"[data-region='blocktime']",CANCELDELETEMESSAGES:"[data-action='cancel-delete-messages']",CONTACT:"[data-region='contact']",CONVERSATIONS:"[data-region='contacts'][data-region-content='conversations']",DELETEALLMESSAGES:"[data-action='delete-all-messages']",DELETEMESSAGES:"[data-action='delete-messages']",LOADINGICON:".loading-icon",MESSAGE:"[data-region='message']",MESSAGERESPONSE:"[data-region='response']",MESSAGES:"[data-region='messages']",MESSAGESAREA:"[data-region='messages-area']",MESSAGINGAREA:"[data-region='messaging-area']",SENDMESSAGE:"[data-action='send-message']",SENDMESSAGETEXT:"[data-region='send-message-txt']",SHOWCONTACTS:"[data-action='show-contacts']",STARTDELETEMESSAGES:"[data-action='start-delete-messages']"};return m.prototype._isSendingMessage=!1,m.prototype._isLoadingMessages=!1,m.prototype._numMessagesDisplayed=0,m.prototype._numMessagesToRetrieve=20,m.prototype._confirmationModal=null,m.prototype._earliestMessageTimestamp=0,m.prototype._timer=null,m.prototype.messageArea=null,m.prototype._init=function(){e.define(this.messageArea.node,[e.events.activate,e.events.up,e.events.down,e.events.enter]),a(window).height()<=670&&(n=400),f.init(this.messageArea.node),this.messageArea.onCustomEvent(k.CONVERSATIONSELECTED,this._viewMessages.bind(this)),this.messageArea.onCustomEvent(k.SENDMESSAGE,this._viewMessages.bind(this)),this.messageArea.onCustomEvent(k.CHOOSEMESSAGESTODELETE,this._chooseMessagesToDelete.bind(this)),this.messageArea.onCustomEvent(k.CANCELDELETEMESSAGES,this._hideDeleteAction.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.SENDMESSAGE,this._sendMessage.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.STARTDELETEMESSAGES,this._startDeleting.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.DELETEMESSAGES,this._deleteMessages.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.DELETEALLMESSAGES,this._deleteAllMessages.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.CANCELDELETEMESSAGES,this._triggerCancelMessagesToDelete.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.MESSAGE,this._toggleMessage.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.SHOWCONTACTS,this._hideMessagingArea.bind(this)),this.messageArea.onDelegateEvent(e.events.up,p.MESSAGE,this._selectPreviousMessage.bind(this)),this.messageArea.onDelegateEvent(e.events.down,p.MESSAGE,this._selectNextMessage.bind(this)),this.messageArea.onDelegateEvent("focus",p.SENDMESSAGETEXT,this._setMessaging.bind(this)),this.messageArea.onDelegateEvent("blur",p.SENDMESSAGETEXT,this._clearMessaging.bind(this)),this.messageArea.onDelegateEvent(e.events.enter,p.SENDMESSAGETEXT,this._sendMessageHandler.bind(this)),a(document).on(f.events.ROW_CHANGE,this._adjustMessagesAreaHeight.bind(this));var b=this.messageArea.find(p.MESSAGES);b.length&&this._addScrollEventListener(b.find(p.MESSAGE).length),this._timer=new l(function(){this._loadNewMessages()}.bind(this)),this._timer.start()},m.prototype._viewMessages=function(e,f){this._numMessagesDisplayed=0,this._timer.stop(),this._earliestMessageTimestamp=0;var g=b.call([{methodname:"core_message_mark_all_messages_as_read",args:{useridto:this.messageArea.getCurrentUserId(),useridfrom:f}}]),h=0;return c.render("core/loading",{}).then(function(a,b){return c.replaceNodeContents(this.messageArea.find(p.MESSAGESAREA),a,b),g[0]}.bind(this)).then(function(){var b=this.messageArea.find(p.CONVERSATIONS+" "+p.CONTACT+"[data-userid='"+f+"']");return b.hasClass("unread")&&(b.removeClass("unread"),a(document).trigger("messagearea:conversationselected",f)),this._getMessages(f)}.bind(this)).then(function(a){return h=a.messages.length,c.render("core_message/message_area_messages_area",a)}).then(function(a,b){c.replaceNodeContents(this.messageArea.find(p.MESSAGESAREA),a,b),this._addScrollEventListener(h),this._timer.restart()}.bind(this)).fail(d.exception)},m.prototype._loadMessages=function(){if(this._isLoadingMessages)return!1;this._isLoadingMessages=!0;var b=0;return c.render("core/loading",{}).then(function(a,b){return c.prependNodeContents(this.messageArea.find(p.MESSAGES),"<div style='text-align:center'>"+a+"</div>",b),this._getMessages(this._getUserId())}.bind(this)).then(function(a){return b=a.messages.length,c.render("core_message/message_area_messages",a)}).then(function(d,e){if(this.messageArea.find(p.MESSAGES+" "+p.LOADINGICON).remove(),b>0){var f=this.messageArea.node.find(p.BLOCKTIME+":first"),g=a(d).find(p.BLOCKTIME+":first").addBack();f.html()==g.html()&&f.remove();var h=this.messageArea.find(p.MESSAGES)[0].scrollHeight;c.prependNodeContents(this.messageArea.find(p.MESSAGES),d,e);var i=this.messageArea.find(p.MESSAGES)[0].scrollHeight;this.messageArea.find(p.MESSAGES).scrollTop(i-h),this._numMessagesDisplayed+=b}this._isLoadingMessages=!1}.bind(this)).fail(d.exception)},m.prototype._loadNewMessages=function(){if(this._isLoadingMessages)return!1;if(!this._getUserId())return!1;this._isLoadingMessages=!0;var b=!1,e=this.messageArea.find(p.MESSAGES);if(0!==e.length){var f=e.scrollTop(),g=e.innerHeight(),h=e[0].scrollHeight;f+g>=h&&(b=!0)}var i=0;return this._getMessages(this._getUserId(),!0).then(function(a){var b=this.messageArea.find(p.MESSAGES);return a.messages=a.messages.filter(function(a){var c=""+a.id+a.isread,d=b.find(p.MESSAGE+'[data-id="'+c+'"]');return!d.length}),i=a.messages.length,c.render("core_message/message_area_messages",a)}.bind(this)).then(function(d,e){i>0&&(d=a(d),d.find(p.BLOCKTIME).remove(),c.appendNodeContents(this.messageArea.find(p.MESSAGES),d,e),b&&this._scrollBottom(),this._numMessagesDisplayed+=i,this._timer.restart())}.bind(this)).always(function(){this._isLoadingMessages=!1}.bind(this)).fail(d.exception)},m.prototype._getMessages=function(a,c){var e={currentuserid:this.messageArea.getCurrentUserId(),otheruserid:a,limitfrom:this._numMessagesDisplayed,limitnum:this._numMessagesToRetrieve,newest:!0};c&&(e.createdfrom=this._earliestMessageTimestamp,e.limitfrom=0,e.limitnum=0);var f=b.call([{methodname:"core_message_data_for_messagearea_messages",args:e}]);return f[0].then(function(a){var b=a.messages;if(b&&b.length){var c=b[b.length-1];this._earliestMessageTimestamp?c.timecreated<this._earliestMessageTimestamp&&(this._earliestMessageTimestamp=c.timecreated+1):this._earliestMessageTimestamp=c.timecreated+1}return a}.bind(this)).fail(function(){this._timer.stop()}.bind(this)).fail(d.exception)},m.prototype._sendMessage=function(){var a=this.messageArea.find(p.SENDMESSAGETEXT),c=a.val();if(""===c.trim())return!1;if(this._isSendingMessage)return!1;this._isSendingMessage=!0;var e=b.call([{methodname:"core_message_send_instant_messages",args:{messages:[{touserid:this._getUserId(),text:c}]}}]);return a.prop("disabled",!0),e[0].then(function(a){if(a.length<0)throw new Error("Invalid response");if(a[0].errormessage)throw new Error(a[0].errormessage);return this.messageArea.trigger(k.MESSAGESENT,[this._getUserId(),c]),this._addMessageToDom()}.bind(this)).then(function(){this._isSendingMessage=!1}.bind(this)).always(function(){a.prop("disabled",!1)}).fail(d.exception)},m.prototype._chooseMessagesToDelete=function(){this.messageArea.find(p.MESSAGESAREA).addClass("editing"),this.messageArea.find(p.MESSAGE).attr("role","checkbox").attr("aria-checked","false")},m.prototype._deleteMessages=function(){var c=this.messageArea.getCurrentUserId(),e=this.messageArea.find(p.MESSAGE+"[aria-checked='true']"),f=[],g=[];e.each(function(b,d){var e=a(d),h=e.data("messageid"),i=e.data("messageread")?1:0;g.push(e),f.push({methodname:"core_message_delete_message",args:{messageid:h,userid:c,read:i}})}),f.length>0?b.call(f)[f.length-1].then(function(){var b=null,c=this.messageArea.find(p.MESSAGE),d=c.last(),e=g[g.length-1];a.each(g,function(a,b){b.remove()}),d.data("id")===e.data("id")&&(b=this.messageArea.find(p.MESSAGE).last()),a.each(g,function(a,b){var c=b.data("blocktime");0===this.messageArea.find(p.MESSAGE+"[data-blocktime='"+c+"']").length&&this.messageArea.find(p.BLOCKTIME+"[data-blocktime='"+c+"']").remove()}.bind(this)),0===this.messageArea.find(p.MESSAGE).length&&this.messageArea.find(p.CONVERSATIONS+" "+p.CONTACT+"[data-userid='"+this._getUserId()+"']").remove(),this.messageArea.trigger(k.MESSAGESDELETED,[this._getUserId(),b])}.bind(this),d.exception):this.messageArea.trigger(k.MESSAGESDELETED,this._getUserId()),this._hideDeleteAction()},m.prototype._addScrollEventListener=function(a){this._scrollBottom(),this._numMessagesDisplayed=a,e.define(this.messageArea.find(p.MESSAGES),[e.events.scrollTop]),this.messageArea.onCustomEvent(e.events.scrollTop,this._loadMessages.bind(this))},m.prototype._deleteAllMessages=function(){this._confirmationModal?this._confirmationModal.show():j.get_strings([{key:"confirm"},{key:"deleteallconfirm",component:"message"}]).done(function(a){h.create({title:a[0],type:h.types.CONFIRM,body:a[1]},this.messageArea.find(p.DELETEALLMESSAGES)).done(function(a){this._confirmationModal=a,a.getRoot().on(i.yes,function(){var a=this._getUserId(),c={methodname:"core_message_delete_conversation",args:{userid:this.messageArea.getCurrentUserId(),otheruserid:a}};b.call([c])[0].then(function(){this.messageArea.find(p.MESSAGESAREA).empty(),this.messageArea.trigger(k.CONVERSATIONDELETED,a),this._hideDeleteAction()}.bind(this),d.exception)}.bind(this)),a.show()}.bind(this))}.bind(this))},m.prototype._hideDeleteAction=function(){this.messageArea.find(p.MESSAGE).removeAttr("role").removeAttr("aria-checked"),this.messageArea.find(p.MESSAGESAREA).removeClass("editing")},m.prototype._triggerCancelMessagesToDelete=function(){this.messageArea.trigger(k.CANCELDELETEMESSAGES)},m.prototype._addMessageToDom=function(){var a=b.call([{methodname:"core_message_data_for_messagearea_get_most_recent_message",args:{currentuserid:this.messageArea.getCurrentUserId(),otheruserid:this._getUserId()}}]);return a[0].then(function(a){return c.render("core_message/message_area_message",a)}).then(function(a,b){c.appendNodeContents(this.messageArea.find(p.MESSAGES),a,b),this.messageArea.find(p.SENDMESSAGETEXT).val("").trigger("input"),this._scrollBottom()}.bind(this)).fail(d.exception)},m.prototype._getUserId=function(){return this.messageArea.find(p.MESSAGES).data("userid")},m.prototype._scrollBottom=function(){var a=this.messageArea.find(p.MESSAGES);0!==a.length&&a.scrollTop(a[0].scrollHeight)},m.prototype._selectPreviousMessage=function(b,c){var d=a(b.target).closest(p.MESSAGE);do d=d.prev();while(d.length&&!d.is(p.MESSAGE));d.focus(),c.originalEvent.preventDefault(),c.originalEvent.stopPropagation()},m.prototype._selectNextMessage=function(b,c){var d=a(b.target).closest(p.MESSAGE);do d=d.next();while(d.length&&!d.is(p.MESSAGE));d.focus(),c.originalEvent.preventDefault(),c.originalEvent.stopPropagation()},m.prototype._setMessaging=function(b){a(b.target).closest(p.MESSAGERESPONSE).addClass("messaging")},m.prototype._clearMessaging=function(b){a(b.target).closest(p.MESSAGERESPONSE).removeClass("messaging")},m.prototype._startDeleting=function(a){var b=new g(this.messageArea);b.chooseMessagesToDelete(),a.preventDefault()},m.prototype._isEditing=function(){return this.messageArea.find(p.MESSAGESAREA).hasClass("editing")},m.prototype._toggleMessage=function(b){if(this._isEditing()){var c=a(b.target).closest(p.MESSAGE);"true"===c.attr("aria-checked")?c.attr("aria-checked","false"):c.attr("aria-checked","true")}},m.prototype._adjustMessagesAreaHeight=function(){var a=this.messageArea.find(p.MESSAGES),b=this.messageArea.find(p.MESSAGERESPONSE),c=b.outerHeight(),d=c-o,e=n-d;a.outerHeight(e)},m.prototype._sendMessageHandler=function(a,b){b.originalEvent.preventDefault(),this._sendMessage()},m.prototype._hideMessagingArea=function(){this.messageArea.find(p.MESSAGINGAREA).removeClass("show-messages").addClass("hide-messages")},m});
\ No newline at end of file
+define(["jquery","core/ajax","core/templates","core/notification","core/custom_interaction_events","core/auto_rows","core_message/message_area_actions","core/modal_factory","core/modal_events","core/str","core_message/message_area_events","core/backoff_timer"],function(a,b,c,d,e,f,g,h,i,j,k,l){function m(a){this.messageArea=a,this._init()}var n=500,o=50,p={BLOCKTIME:"[data-region='blocktime']",CANCELDELETEMESSAGES:"[data-action='cancel-delete-messages']",CONTACT:"[data-region='contact']",CONVERSATIONS:"[data-region='contacts'][data-region-content='conversations']",DELETEALLMESSAGES:"[data-action='delete-all-messages']",DELETEMESSAGES:"[data-action='delete-messages']",LOADINGICON:".loading-icon",MESSAGE:"[data-region='message']",MESSAGERESPONSE:"[data-region='response']",MESSAGES:"[data-region='messages']",MESSAGESAREA:"[data-region='messages-area']",MESSAGINGAREA:"[data-region='messaging-area']",SENDMESSAGE:"[data-action='send-message']",SENDMESSAGETEXT:"[data-region='send-message-txt']",SHOWCONTACTS:"[data-action='show-contacts']",STARTDELETEMESSAGES:"[data-action='start-delete-messages']"},q=1e3;return m.prototype._isSendingMessage=!1,m.prototype._isLoadingMessages=!1,m.prototype._numMessagesDisplayed=0,m.prototype._numMessagesToRetrieve=20,m.prototype._confirmationModal=null,m.prototype._earliestMessageTimestamp=0,m.prototype._backoffTimer=null,m.prototype.messageArea=null,m.prototype._init=function(){e.define(this.messageArea.node,[e.events.activate,e.events.up,e.events.down,e.events.enter]),a(window).height()<=670&&(n=400),f.init(this.messageArea.node),this.messageArea.onCustomEvent(k.CONVERSATIONSELECTED,this._viewMessages.bind(this)),this.messageArea.onCustomEvent(k.SENDMESSAGE,this._viewMessages.bind(this)),this.messageArea.onCustomEvent(k.CHOOSEMESSAGESTODELETE,this._chooseMessagesToDelete.bind(this)),this.messageArea.onCustomEvent(k.CANCELDELETEMESSAGES,this._hideDeleteAction.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.SENDMESSAGE,this._sendMessage.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.STARTDELETEMESSAGES,this._startDeleting.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.DELETEMESSAGES,this._deleteMessages.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.DELETEALLMESSAGES,this._deleteAllMessages.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.CANCELDELETEMESSAGES,this._triggerCancelMessagesToDelete.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.MESSAGE,this._toggleMessage.bind(this)),this.messageArea.onDelegateEvent(e.events.activate,p.SHOWCONTACTS,this._hideMessagingArea.bind(this)),this.messageArea.onDelegateEvent(e.events.up,p.MESSAGE,this._selectPreviousMessage.bind(this)),this.messageArea.onDelegateEvent(e.events.down,p.MESSAGE,this._selectNextMessage.bind(this)),this.messageArea.onDelegateEvent("focus",p.SENDMESSAGETEXT,this._setMessaging.bind(this)),this.messageArea.onDelegateEvent("blur",p.SENDMESSAGETEXT,this._clearMessaging.bind(this)),this.messageArea.onDelegateEvent(e.events.enter,p.SENDMESSAGETEXT,this._sendMessageHandler.bind(this)),a(document).on(f.events.ROW_CHANGE,this._adjustMessagesAreaHeight.bind(this));var b=this.messageArea.find(p.MESSAGES);b.length&&this._addScrollEventListener(b.find(p.MESSAGE).length),this._backoffTimer=new l(this._loadNewMessages.bind(this),l.getIncrementalCallback(this.messageArea.pollmin*q,q,this.messageArea.pollmax*q,this.messageArea.polltimeout*q)),this._backoffTimer.start()},m.prototype._viewMessages=function(e,f){this._numMessagesDisplayed=0,this._backoffTimer.stop(),this._earliestMessageTimestamp=0;var g=b.call([{methodname:"core_message_mark_all_messages_as_read",args:{useridto:this.messageArea.getCurrentUserId(),useridfrom:f}}]),h=0;return c.render("core/loading",{}).then(function(a,b){return c.replaceNodeContents(this.messageArea.find(p.MESSAGESAREA),a,b),g[0]}.bind(this)).then(function(){var b=this.messageArea.find(p.CONVERSATIONS+" "+p.CONTACT+"[data-userid='"+f+"']");return b.hasClass("unread")&&(b.removeClass("unread"),a(document).trigger("messagearea:conversationselected",f)),this._getMessages(f)}.bind(this)).then(function(a){return h=a.messages.length,c.render("core_message/message_area_messages_area",a)}).then(function(a,b){c.replaceNodeContents(this.messageArea.find(p.MESSAGESAREA),a,b),this._addScrollEventListener(h),this._backoffTimer.restart()}.bind(this)).fail(d.exception)},m.prototype._loadMessages=function(){if(this._isLoadingMessages)return!1;this._isLoadingMessages=!0;var b=0;return c.render("core/loading",{}).then(function(a,b){return c.prependNodeContents(this.messageArea.find(p.MESSAGES),"<div style='text-align:center'>"+a+"</div>",b),this._getMessages(this._getUserId())}.bind(this)).then(function(a){return b=a.messages.length,c.render("core_message/message_area_messages",a)}).then(function(d,e){if(this.messageArea.find(p.MESSAGES+" "+p.LOADINGICON).remove(),b>0){var f=this.messageArea.node.find(p.BLOCKTIME+":first"),g=a(d).find(p.BLOCKTIME+":first").addBack();f.html()==g.html()&&f.remove();var h=this.messageArea.find(p.MESSAGES)[0].scrollHeight;c.prependNodeContents(this.messageArea.find(p.MESSAGES),d,e);var i=this.messageArea.find(p.MESSAGES)[0].scrollHeight;this.messageArea.find(p.MESSAGES).scrollTop(i-h),this._numMessagesDisplayed+=b}this._isLoadingMessages=!1}.bind(this)).fail(d.exception)},m.prototype._loadNewMessages=function(){if(this._isLoadingMessages)return!1;if(!this._getUserId())return!1;this._isLoadingMessages=!0;var b=!1,e=this.messageArea.find(p.MESSAGES);if(0!==e.length){var f=e.scrollTop(),g=e.innerHeight(),h=e[0].scrollHeight;f+g>=h&&(b=!0)}var i=0;return this._getMessages(this._getUserId(),!0).then(function(a){var b=this.messageArea.find(p.MESSAGES);return a.messages=a.messages.filter(function(a){var c=""+a.id+a.isread,d=b.find(p.MESSAGE+'[data-id="'+c+'"]');return!d.length}),i=a.messages.length,c.render("core_message/message_area_messages",a)}.bind(this)).then(function(d,e){i>0&&(d=a(d),d.find(p.BLOCKTIME).remove(),c.appendNodeContents(this.messageArea.find(p.MESSAGES),d,e),b&&this._scrollBottom(),this._numMessagesDisplayed+=i,this._backoffTimer.restart())}.bind(this)).always(function(){this._isLoadingMessages=!1}.bind(this)).fail(d.exception)},m.prototype._getMessages=function(a,c){var e={currentuserid:this.messageArea.getCurrentUserId(),otheruserid:a,limitfrom:this._numMessagesDisplayed,limitnum:this._numMessagesToRetrieve,newest:!0};c&&(e.timefrom=this._earliestMessageTimestamp,e.limitfrom=0,e.limitnum=0);var f=b.call([{methodname:"core_message_data_for_messagearea_messages",args:e}]);return f[0].then(function(a){var b=a.messages;if(b&&b.length){var c=b[b.length-1];this._earliestMessageTimestamp?c.timecreated<this._earliestMessageTimestamp&&(this._earliestMessageTimestamp=c.timecreated+1):this._earliestMessageTimestamp=c.timecreated+1}return a}.bind(this)).fail(function(a){this._backoffTimer.stop(),d.exception(a)}.bind(this))},m.prototype._sendMessage=function(){var a=this.messageArea.find(p.SENDMESSAGETEXT),c=a.val();if(""===c.trim())return!1;if(this._isSendingMessage)return!1;this._isSendingMessage=!0;var e=b.call([{methodname:"core_message_send_instant_messages",args:{messages:[{touserid:this._getUserId(),text:c}]}}]);return a.prop("disabled",!0),e[0].then(function(a){if(a.length<0)throw new Error("Invalid response");if(a[0].errormessage)throw new Error(a[0].errormessage);return this.messageArea.trigger(k.MESSAGESENT,[this._getUserId(),c]),this._addMessageToDom()}.bind(this)).then(function(){this._isSendingMessage=!1}.bind(this)).always(function(){a.prop("disabled",!1)}).fail(d.exception)},m.prototype._chooseMessagesToDelete=function(){this.messageArea.find(p.MESSAGESAREA).addClass("editing"),this.messageArea.find(p.MESSAGE).attr("role","checkbox").attr("aria-checked","false")},m.prototype._deleteMessages=function(){var c=this.messageArea.getCurrentUserId(),e=this.messageArea.find(p.MESSAGE+"[aria-checked='true']"),f=[],g=[];e.each(function(b,d){var e=a(d),h=e.data("messageid"),i=e.data("messageread")?1:0;g.push(e),f.push({methodname:"core_message_delete_message",args:{messageid:h,userid:c,read:i}})}),f.length>0?b.call(f)[f.length-1].then(function(){var b=null,c=this.messageArea.find(p.MESSAGE),d=c.last(),e=g[g.length-1];a.each(g,function(a,b){b.remove()}),d.data("id")===e.data("id")&&(b=this.messageArea.find(p.MESSAGE).last()),a.each(g,function(a,b){var c=b.data("blocktime");0===this.messageArea.find(p.MESSAGE+"[data-blocktime='"+c+"']").length&&this.messageArea.find(p.BLOCKTIME+"[data-blocktime='"+c+"']").remove()}.bind(this)),0===this.messageArea.find(p.MESSAGE).length&&this.messageArea.find(p.CONVERSATIONS+" "+p.CONTACT+"[data-userid='"+this._getUserId()+"']").remove(),this.messageArea.trigger(k.MESSAGESDELETED,[this._getUserId(),b])}.bind(this),d.exception):this.messageArea.trigger(k.MESSAGESDELETED,this._getUserId()),this._hideDeleteAction()},m.prototype._addScrollEventListener=function(a){this._scrollBottom(),this._numMessagesDisplayed=a,e.define(this.messageArea.find(p.MESSAGES),[e.events.scrollTop]),this.messageArea.onCustomEvent(e.events.scrollTop,this._loadMessages.bind(this))},m.prototype._deleteAllMessages=function(){this._confirmationModal?this._confirmationModal.show():j.get_strings([{key:"confirm"},{key:"deleteallconfirm",component:"message"}]).done(function(a){h.create({title:a[0],type:h.types.CONFIRM,body:a[1]},this.messageArea.find(p.DELETEALLMESSAGES)).done(function(a){this._confirmationModal=a,a.getRoot().on(i.yes,function(){var a=this._getUserId(),c={methodname:"core_message_delete_conversation",args:{userid:this.messageArea.getCurrentUserId(),otheruserid:a}};b.call([c])[0].then(function(){this.messageArea.find(p.MESSAGESAREA).empty(),this.messageArea.trigger(k.CONVERSATIONDELETED,a),this._hideDeleteAction()}.bind(this),d.exception)}.bind(this)),a.show()}.bind(this))}.bind(this))},m.prototype._hideDeleteAction=function(){this.messageArea.find(p.MESSAGE).removeAttr("role").removeAttr("aria-checked"),this.messageArea.find(p.MESSAGESAREA).removeClass("editing")},m.prototype._triggerCancelMessagesToDelete=function(){this.messageArea.trigger(k.CANCELDELETEMESSAGES)},m.prototype._addMessageToDom=function(){var a=b.call([{methodname:"core_message_data_for_messagearea_get_most_recent_message",args:{currentuserid:this.messageArea.getCurrentUserId(),otheruserid:this._getUserId()}}]);return a[0].then(function(a){return c.render("core_message/message_area_message",a)}).then(function(a,b){c.appendNodeContents(this.messageArea.find(p.MESSAGES),a,b),this.messageArea.find(p.SENDMESSAGETEXT).val("").trigger("input"),this._scrollBottom()}.bind(this)).fail(d.exception)},m.prototype._getUserId=function(){return this.messageArea.find(p.MESSAGES).data("userid")},m.prototype._scrollBottom=function(){var a=this.messageArea.find(p.MESSAGES);0!==a.length&&a.scrollTop(a[0].scrollHeight)},m.prototype._selectPreviousMessage=function(b,c){var d=a(b.target).closest(p.MESSAGE);do d=d.prev();while(d.length&&!d.is(p.MESSAGE));d.focus(),c.originalEvent.preventDefault(),c.originalEvent.stopPropagation()},m.prototype._selectNextMessage=function(b,c){var d=a(b.target).closest(p.MESSAGE);do d=d.next();while(d.length&&!d.is(p.MESSAGE));d.focus(),c.originalEvent.preventDefault(),c.originalEvent.stopPropagation()},m.prototype._setMessaging=function(b){a(b.target).closest(p.MESSAGERESPONSE).addClass("messaging")},m.prototype._clearMessaging=function(b){a(b.target).closest(p.MESSAGERESPONSE).removeClass("messaging")},m.prototype._startDeleting=function(a){var b=new g(this.messageArea);b.chooseMessagesToDelete(),a.preventDefault()},m.prototype._isEditing=function(){return this.messageArea.find(p.MESSAGESAREA).hasClass("editing")},m.prototype._toggleMessage=function(b){if(this._isEditing()){var c=a(b.target).closest(p.MESSAGE);"true"===c.attr("aria-checked")?c.attr("aria-checked","false"):c.attr("aria-checked","true")}},m.prototype._adjustMessagesAreaHeight=function(){var a=this.messageArea.find(p.MESSAGES),b=this.messageArea.find(p.MESSAGERESPONSE),c=b.outerHeight(),d=c-o,e=n-d;a.outerHeight(e)},m.prototype._sendMessageHandler=function(a,b){b.originalEvent.preventDefault(),this._sendMessage()},m.prototype._hideMessagingArea=function(){this.messageArea.find(p.MESSAGINGAREA).removeClass("show-messages").addClass("hide-messages")},m});
\ No newline at end of file
diff --git a/message/amd/src/message_area.js b/message/amd/src/message_area.js
index 681712ac4419b..73bad76ce6618 100644
--- a/message/amd/src/message_area.js
+++ b/message/amd/src/message_area.js
@@ -29,15 +29,30 @@ define(['jquery', 'core_message/message_area_contacts', 'core_message/message_ar
          * Messagearea class.
          *
          * @param {String} selector The selector for the page region containing the message area.
+         * @param {int} pollmin
+         * @param {int} pollmax
+         * @param {int} polltimeout
          */
-        function Messagearea(selector) {
+        function Messagearea(selector, pollmin, pollmax, polltimeout) {
             this.node = $(selector);
+            this.pollmin = pollmin;
+            this.pollmax = pollmax;
+            this.polltimeout = polltimeout;
             this._init();
         }
 
         /** @type {jQuery} The jQuery node for the page region containing the message area. */
         Messagearea.prototype.node = null;
 
+        /** @type {int} The minimum time to poll for messages. */
+        Messagearea.prototype.pollmin = null;
+
+        /** @type {int} The maximum time to poll for messages. */
+        Messagearea.prototype.pollmax = null;
+
+        /** @type {int} The time used once we have reached the maximum polling time. */
+        Messagearea.prototype.polltimeout = null;
+
         /**
          * Initialise the other objects we require.
          */
diff --git a/message/amd/src/message_area_messages.js b/message/amd/src/message_area_messages.js
index a24ef0b0990e2..24d3c8ad60cc1 100644
--- a/message/amd/src/message_area_messages.js
+++ b/message/amd/src/message_area_messages.js
@@ -53,6 +53,9 @@ define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/cust
             STARTDELETEMESSAGES: "[data-action='start-delete-messages']"
         };
 
+        /** @type {int} The number of milliseconds in a second. */
+        var MILLISECONDSINSEC = 1000;
+
         /**
          * Messages class.
          *
@@ -81,8 +84,8 @@ define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/cust
         /** @type {int} the timestamp for the earliest visible message */
         Messages.prototype._earliestMessageTimestamp = 0;
 
-        /** @type {BackOffTime} the backoff timer */
-        Messages.prototype._timer = null;
+        /** @type {BackOffTimer} the backoff timer */
+        Messages.prototype._backoffTimer = null;
 
         /** @type {Messagearea} The messaging area object. */
         Messages.prototype.messageArea = null;
@@ -146,12 +149,12 @@ define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/cust
             }
 
             // Create a timer to poll the server for new messages.
-            this._timer = new BackOffTimer(function() {
-                this._loadNewMessages();
-            }.bind(this));
+            this._backoffTimer = new BackOffTimer(this._loadNewMessages.bind(this),
+                BackOffTimer.getIncrementalCallback(this.messageArea.pollmin * MILLISECONDSINSEC, MILLISECONDSINSEC,
+                    this.messageArea.pollmax * MILLISECONDSINSEC, this.messageArea.polltimeout * MILLISECONDSINSEC));
 
             // Start the timer.
-            this._timer.start();
+            this._backoffTimer.start();
         };
 
         /**
@@ -166,7 +169,7 @@ define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/cust
             // We are viewing another user, or re-loading the panel, so set number of messages displayed to 0.
             this._numMessagesDisplayed = 0;
             // Stop the existing timer so we can set up the new user's messages.
-            this._timer.stop();
+            this._backoffTimer.stop();
             // Reset the earliest timestamp when we change the messages view.
             this._earliestMessageTimestamp = 0;
 
@@ -203,7 +206,7 @@ define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/cust
                 Templates.replaceNodeContents(this.messageArea.find(SELECTORS.MESSAGESAREA), html, js);
                 this._addScrollEventListener(numberreceived);
                 // Restart the poll timer.
-                this._timer.restart();
+                this._backoffTimer.restart();
             }.bind(this)).fail(Notification.exception);
         };
 
@@ -321,7 +324,7 @@ define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/cust
                     // Increment the number of messages displayed.
                     this._numMessagesDisplayed += numberreceived;
                     // Reset the poll timer because the user may be active.
-                    this._timer.restart();
+                    this._backoffTimer.restart();
                 }
             }.bind(this)).always(function() {
                 // Mark that we are no longer busy loading data.
@@ -349,7 +352,7 @@ define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/cust
             // If we're trying to load new messages since the message UI was
             // rendered. Used for ajax polling while user is on the message UI.
             if (fromTimestamp) {
-                args.createdfrom = this._earliestMessageTimestamp;
+                args.timefrom = this._earliestMessageTimestamp;
                 // Remove limit and offset. We want all new messages.
                 args.limitfrom = 0;
                 args.limitnum = 0;
@@ -381,10 +384,11 @@ define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/cust
                 }
 
                 return data;
-            }.bind(this)).fail(function() {
+            }.bind(this)).fail(function(ex) {
                 // Stop the timer if we received an error so that we don't keep spamming the server.
-                this._timer.stop();
-            }.bind(this)).fail(Notification.exception);
+                this._backoffTimer.stop();
+                Notification.exception(ex);
+            }.bind(this));
         };
 
         /**
diff --git a/message/classes/api.php b/message/classes/api.php
index 2d6150f03862f..25910dae2baf5 100644
--- a/message/classes/api.php
+++ b/message/classes/api.php
@@ -291,31 +291,29 @@ public static function get_contacts($userid, $limitfrom = 0, $limitnum = 0) {
      * @param int $limitfrom
      * @param int $limitnum
      * @param string $sort
-     * @param int $createdfrom the timestamp from which the messages were created
-     * @param int $createdto the time up until which the message was created
+     * @param int $timefrom the time from the message being sent
+     * @param int $timeto the time up until the message being sent
      * @return array
      */
     public static function get_messages($userid, $otheruserid, $limitfrom = 0, $limitnum = 0,
-        $sort = 'timecreated ASC', $createdfrom = 0, $createdto = 0) {
+        $sort = 'timecreated ASC', $timefrom = 0, $timeto = 0) {
 
-        if (!empty($createdfrom)) {
+        if (!empty($timefrom)) {
             // Check the cache to see if we even need to do a DB query.
-            $cache = \cache::make('core', 'message_last_created');
-            $ids = [$otheruserid, $userid];
-            sort($ids);
-            $key = implode('_', $ids);
+            $cache = \cache::make('core', 'message_time_last_message_between_users');
+            $key = helper::get_last_message_time_created_cache_key($otheruserid, $userid);
             $lastcreated = $cache->get($key);
 
             // The last known message time is earlier than the one being requested so we can
             // just return an empty result set rather than having to query the DB.
-            if ($lastcreated && $lastcreated < $createdfrom) {
+            if ($lastcreated && $lastcreated < $timefrom) {
                 return [];
             }
         }
 
         $arrmessages = array();
         if ($messages = helper::get_messages($userid, $otheruserid, 0, $limitfrom, $limitnum,
-                                             $sort, $createdfrom, $createdto)) {
+                                             $sort, $timefrom, $timeto)) {
 
             $arrmessages = helper::create_messages($userid, $messages);
         }
diff --git a/message/classes/helper.php b/message/classes/helper.php
index 3a4c70d730d10..8ae5ea67172e5 100644
--- a/message/classes/helper.php
+++ b/message/classes/helper.php
@@ -43,12 +43,12 @@ class helper {
      * @param int $limitfrom
      * @param int $limitnum
      * @param string $sort
-     * @param int $createdfrom the time from which the message was created
-     * @param int $createdto the time up until which the message was created
+     * @param int $timefrom the time from the message being sent
+     * @param int $timeto the time up until the message being sent
      * @return array of messages
      */
     public static function get_messages($userid, $otheruserid, $timedeleted = 0, $limitfrom = 0, $limitnum = 0,
-                                        $sort = 'timecreated ASC', $createdfrom = 0, $createdto = 0) {
+                                        $sort = 'timecreated ASC', $timefrom = 0, $timeto = 0) {
         global $DB;
 
         $messageid = $DB->sql_concat("'message_'", 'id');
@@ -77,16 +77,16 @@ public static function get_messages($userid, $otheruserid, $timedeleted = 0, $li
                          $otheruserid, $userid, $timedeleted);
         $where = array();
 
-        if (!empty($createdfrom)) {
+        if (!empty($timefrom)) {
             $where[] = 'AND timecreated >= ?';
-            $params1[] = $createdfrom;
-            $params2[] = $createdfrom;
+            $params1[] = $timefrom;
+            $params2[] = $timefrom;
         }
 
-        if (!empty($createdto)) {
+        if (!empty($timeto)) {
             $where[] = 'AND timecreated <= ?';
-            $params1[] = $createdto;
-            $params2[] = $createdto;
+            $params1[] = $timeto;
+            $params2[] = $timeto;
         }
 
         $sql = str_replace('%where%', implode(' ', $where), $sql);
@@ -270,4 +270,17 @@ public static function togglecontact_link_params($user, $iscontact = false) {
 
         return $params;
     }
+
+    /**
+     * Returns the cache key for the time created value of the last message between two users.
+     *
+     * @param int $userid
+     * @param int $user2id
+     * @return string
+     */
+    public static function get_last_message_time_created_cache_key($userid, $user2id) {
+        $ids = [$userid, $user2id];
+        sort($ids);
+        return implode('_', $ids);
+    }
 }
diff --git a/message/classes/output/messagearea/message_area.php b/message/classes/output/messagearea/message_area.php
index a3dd242de31bd..3c765917710b6 100644
--- a/message/classes/output/messagearea/message_area.php
+++ b/message/classes/output/messagearea/message_area.php
@@ -63,6 +63,21 @@ class message_area implements templatable, renderable {
      */
     public $requestedconversation;
 
+    /**
+     * @var int The minimum time to poll for messages.
+     */
+    public $pollmin;
+
+    /**
+     * @var int The maximum time to poll for messages.
+     */
+    public $pollmax;
+
+    /**
+     * @var int The time used once we have reached the maximum polling time.
+     */
+    public $polltimeout;
+
     /**
      * Constructor.
      *
@@ -71,13 +86,20 @@ class message_area implements templatable, renderable {
      * @param array $contacts
      * @param array|null $messages
      * @param bool $requestedconversation
+     * @param int $pollmin
+     * @param int $pollmax
+     * @param int $polltimeout
      */
-    public function __construct($userid, $otheruserid, $contacts, $messages, $requestedconversation) {
+    public function __construct($userid, $otheruserid, $contacts, $messages, $requestedconversation, $pollmin, $pollmax,
+            $polltimeout) {
         $this->userid = $userid;
         $this->otheruserid = $otheruserid;
         $this->contacts = $contacts;
         $this->messages = $messages;
         $this->requestedconversation = $requestedconversation;
+        $this->pollmin = $pollmin;
+        $this->pollmax = $pollmax;
+        $this->polltimeout = $polltimeout;
     }
 
     public function export_for_template(\renderer_base $output) {
@@ -89,6 +111,9 @@ public function export_for_template(\renderer_base $output) {
         $data->messages = $messages->export_for_template($output);
         $data->isconversation = true;
         $data->requestedconversation = $this->requestedconversation;
+        $data->pollmin = $this->pollmin;
+        $data->pollmax = $this->pollmax;
+        $data->polltimeout = $this->polltimeout;
 
         return $data;
     }
diff --git a/message/classes/message_last_created_cache_source.php b/message/classes/time_last_message_between_users.php
similarity index 79%
rename from message/classes/message_last_created_cache_source.php
rename to message/classes/time_last_message_between_users.php
index ea0cd05df1b12..750a552dbbf77 100644
--- a/message/classes/message_last_created_cache_source.php
+++ b/message/classes/time_last_message_between_users.php
@@ -15,7 +15,7 @@
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
 /**
- * Cache data source for the last created message between users.
+ * Cache data source for the time of the last message between users.
  *
  * @package    core_message
  * @category   cache
@@ -23,32 +23,33 @@
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 
+namespace core_message;
 
 defined('MOODLE_INTERNAL') || die();
 
 /**
- * Cache data source for the last created message between users.
+ * Cache data source for the time of the last message between users.
  *
  * @package    core_message
  * @category   cache
  * @copyright  2016 Ryan Wyllie <ryan@moodle.com>
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
-class message_last_created_cache_source implements \cache_data_source {
+class time_last_message_between_users implements \cache_data_source {
 
-    /** @var message_last_created_cache_source the singleton instance of this class. */
+    /** @var time_last_message_between_users the singleton instance of this class. */
     protected static $instance = null;
 
     /**
      * Returns an instance of the data source class that the cache can use for loading data using the other methods
      * specified by the cache_data_source interface.
      *
-     * @param cache_definition $definition
+     * @param \cache_definition $definition
      * @return object
      */
-    public static function get_instance_for_cache(cache_definition $definition) {
+    public static function get_instance_for_cache(\cache_definition $definition) {
         if (is_null(self::$instance)) {
-            self::$instance = new message_last_created_cache_source();
+            self::$instance = new time_last_message_between_users();
         }
         return self::$instance;
     }
@@ -62,7 +63,7 @@ public static function get_instance_for_cache(cache_definition $definition) {
     public function load_for_cache($key) {
         list($userid1, $userid2) = explode('_', $key);
 
-        $message = \core_message\api::get_most_recent_message($userid1, $userid2);
+        $message = api::get_most_recent_message($userid1, $userid2);
 
         if ($message) {
             return $message->timecreated;
diff --git a/message/externallib.php b/message/externallib.php
index 98b5634c9d6c7..a3b4247b746fb 100644
--- a/message/externallib.php
+++ b/message/externallib.php
@@ -901,7 +901,7 @@ public static function data_for_messagearea_messages_parameters() {
                 'limitfrom' => new external_value(PARAM_INT, 'Limit from', VALUE_DEFAULT, 0),
                 'limitnum' => new external_value(PARAM_INT, 'Limit number', VALUE_DEFAULT, 0),
                 'newest' => new external_value(PARAM_BOOL, 'Newest first?', VALUE_DEFAULT, false),
-                'createdfrom' => new external_value(PARAM_INT,
+                'timefrom' => new external_value(PARAM_INT,
                     'The timestamp from which the messages were created', VALUE_DEFAULT, 0),
             )
         );
@@ -920,7 +920,7 @@ public static function data_for_messagearea_messages_parameters() {
      * @since 3.2
      */
     public static function data_for_messagearea_messages($currentuserid, $otheruserid, $limitfrom = 0, $limitnum = 0,
-                                                         $newest = false, $createdfrom = 0) {
+                                                         $newest = false, $timefrom = 0) {
         global $CFG, $PAGE, $USER;
 
         // Check if messaging is enabled.
@@ -936,7 +936,7 @@ public static function data_for_messagearea_messages($currentuserid, $otheruseri
             'limitfrom' => $limitfrom,
             'limitnum' => $limitnum,
             'newest' => $newest,
-            'createdfrom' => $createdfrom,
+            'timefrom' => $timefrom,
         );
         self::validate_parameters(self::data_for_messagearea_messages_parameters(), $params);
         self::validate_context($systemcontext);
@@ -959,18 +959,18 @@ public static function data_for_messagearea_messages($currentuserid, $otheruseri
         // case those messages will be lost.
         //
         // Instead we ignore the current time in the result set to ensure that second is allowed to finish.
-        if (!empty($createdfrom)) {
-            $createdto = time() - 1;
+        if (!empty($timefrom)) {
+            $timeto = time() - 1;
         } else {
-            $createdto = 0;
+            $timeto = 0;
         }
 
         // No requesting messages from the current time, as stated above.
-        if ($createdfrom == time()) {
-            $mesages = [];
+        if ($timefrom == time()) {
+            $messages = [];
         } else {
             $messages = \core_message\api::get_messages($currentuserid, $otheruserid, $limitfrom,
-                                                        $limitnum, $sort, $createdfrom, $createdto);
+                                                        $limitnum, $sort, $timefrom, $timeto);
         }
 
         $messages = new \core_message\output\messagearea\messages($currentuserid, $otheruserid, $messages);
diff --git a/message/index.php b/message/index.php
index 0f834a88a0520..5789216570f84 100644
--- a/message/index.php
+++ b/message/index.php
@@ -127,8 +127,11 @@
     $messages = \core_message\api::get_messages($user1->id, $user2->id, 0, 20, 'timecreated DESC');
 }
 
+$pollmin = !empty($CFG->messagingminpoll) ? $CFG->messagingminpoll : MESSAGE_DEFAULT_MIN_POLL_IN_SECONDS;
+$pollmax = !empty($CFG->messagingmaxpoll) ? $CFG->messagingmaxpoll : MESSAGE_DEFAULT_MAX_POLL_IN_SECONDS;
+$polltimeout = !empty($CFG->messagingtimeoutpoll) ? $CFG->messagingtimeoutpoll : MESSAGE_DEFAULT_TIMEOUT_POLL_IN_SECONDS;
 $messagearea = new \core_message\output\messagearea\message_area($user1->id, $user2->id, $conversations, $messages,
-    $requestedconversation);
+    $requestedconversation, $pollmin, $pollmax, $polltimeout);
 
 // Now the page contents.
 echo $OUTPUT->header();
diff --git a/message/lib.php b/message/lib.php
index 34431beabbe1d..f3820c39ceaa5 100644
--- a/message/lib.php
+++ b/message/lib.php
@@ -76,6 +76,13 @@
  */
 define('MESSAGE_DEFAULT_PERMITTED', 'permitted');
 
+/**
+ * Set default values for polling.
+ */
+define('MESSAGE_DEFAULT_MIN_POLL_IN_SECONDS', 10);
+define('MESSAGE_DEFAULT_MAX_POLL_IN_SECONDS', 2 * MINSECS);
+define('MESSAGE_DEFAULT_TIMEOUT_POLL_IN_SECONDS', 5 * MINSECS);
+
 /**
  * Retrieve users blocked by $user1
  *
diff --git a/message/templates/message_area.mustache b/message/templates/message_area.mustache
index 15af327e0ba0b..8667f416daadb 100644
--- a/message/templates/message_area.mustache
+++ b/message/templates/message_area.mustache
@@ -32,7 +32,7 @@
 {{#js}}
     require(['core_message/message_area'],
         function(Messagearea) {
-            new Messagearea('.messaging-area-container');
+            new Messagearea('.messaging-area-container', {{pollmin}}, {{pollmax}}, {{polltimeout}});
         }
     );
 {{/js}}
diff --git a/message/tests/api_test.php b/message/tests/api_test.php
index 15376e049370d..9c52f86f9903d 100644
--- a/message/tests/api_test.php
+++ b/message/tests/api_test.php
@@ -957,7 +957,7 @@ public function is_user_enabled() {
     /**
      * Test retrieving messages by providing a minimum timecreated value.
      */
-    public function test_get_messages_created_from_only() {
+    public function test_get_messages_time_from_only() {
         // Create some users.
         $user1 = self::getDataGenerator()->create_user();
         $user2 = self::getDataGenerator()->create_user();
@@ -972,7 +972,7 @@ public function test_get_messages_created_from_only() {
         $this->send_fake_message($user1, $user2, 'Message 3', 0, $time + 3);
         $this->send_fake_message($user2, $user1, 'Message 4', 0, $time + 4);
 
-        // Retrieve the messages.
+        // Retrieve the messages from $time, which should be all of them.
         $messages = \core_message\api::get_messages($user1->id, $user2->id, 0, 0, 'timecreated ASC', $time);
 
         // Confirm the message data is correct.
@@ -988,7 +988,7 @@ public function test_get_messages_created_from_only() {
         $this->assertContains('Message 3', $message3->text);
         $this->assertContains('Message 4', $message4->text);
 
-        // Retrieve the messages.
+        // Retrieve the messages from $time + 3, which should only be the 2 last messages.
         $messages = \core_message\api::get_messages($user1->id, $user2->id, 0, 0, 'timecreated ASC', $time + 3);
 
         // Confirm the message data is correct.
@@ -1004,7 +1004,7 @@ public function test_get_messages_created_from_only() {
     /**
      * Test retrieving messages by providing a maximum timecreated value.
      */
-    public function test_get_messages_created_to_only() {
+    public function test_get_messages_time_to_only() {
         // Create some users.
         $user1 = self::getDataGenerator()->create_user();
         $user2 = self::getDataGenerator()->create_user();
@@ -1019,7 +1019,7 @@ public function test_get_messages_created_to_only() {
         $this->send_fake_message($user1, $user2, 'Message 3', 0, $time + 3);
         $this->send_fake_message($user2, $user1, 'Message 4', 0, $time + 4);
 
-        // Retrieve the messages.
+        // Retrieve the messages up until $time + 4, which should be all of them.
         $messages = \core_message\api::get_messages($user1->id, $user2->id, 0, 0, 'timecreated ASC', 0, $time + 4);
 
         // Confirm the message data is correct.
@@ -1035,7 +1035,7 @@ public function test_get_messages_created_to_only() {
         $this->assertContains('Message 3', $message3->text);
         $this->assertContains('Message 4', $message4->text);
 
-        // Retrieve the messages.
+        // Retrieve the messages up until $time + 2, which should be the first two.
         $messages = \core_message\api::get_messages($user1->id, $user2->id, 0, 0, 'timecreated ASC', 0, $time + 2);
 
         // Confirm the message data is correct.
@@ -1051,7 +1051,7 @@ public function test_get_messages_created_to_only() {
     /**
      * Test retrieving messages by providing a minimum and maximum timecreated value.
      */
-    public function test_get_messages_created_from_and_to() {
+    public function test_get_messages_time_from_and_to() {
         // Create some users.
         $user1 = self::getDataGenerator()->create_user();
         $user2 = self::getDataGenerator()->create_user();
@@ -1066,7 +1066,7 @@ public function test_get_messages_created_from_and_to() {
         $this->send_fake_message($user1, $user2, 'Message 3', 0, $time + 3);
         $this->send_fake_message($user2, $user1, 'Message 4', 0, $time + 4);
 
-        // Retrieve the messages.
+        // Retrieve the messages from $time + 2 up until $time + 3, which should be 2nd and 3rd message.
         $messages = \core_message\api::get_messages($user1->id, $user2->id, 0, 0, 'timecreated ASC', $time + 2, $time + 3);
 
         // Confirm the message data is correct.
diff --git a/message/tests/externallib_test.php b/message/tests/externallib_test.php
index c739b1a4e3664..3f1e38e3dd767 100644
--- a/message/tests/externallib_test.php
+++ b/message/tests/externallib_test.php
@@ -1982,7 +1982,7 @@ public function test_messagearea_messages() {
     /**
      * Tests retrieving messages.
      */
-    public function test_messagearea_messages_createfrom() {
+    public function test_messagearea_messages_timefrom() {
         $this->resetAfterTest(true);
 
         // Create some users.
@@ -1999,7 +1999,7 @@ public function test_messagearea_messages_createfrom() {
         $this->send_message($user1, $user2, 'Message 3', 0, $time - 2);
         $this->send_message($user2, $user1, 'Message 4', 0, $time - 1);
 
-        // Retrieve the messages.
+        // Retrieve the messages from $time - 3, which should be the 3 most recent messages.
         $result = core_message_external::data_for_messagearea_messages($user1->id, $user2->id, 0, 0, false, $time - 3);
 
         // We need to execute the return values cleaning process to simulate the web service server.

From af5765b3fbe82ea8e55d8ddcc3fe220ff845fef9 Mon Sep 17 00:00:00 2001
From: Mark Nelson <markn@moodle.com>
Date: Tue, 15 Nov 2016 14:28:15 +0800
Subject: [PATCH 3/3] MDL-56139 core_message: removed unused constants

---
 lib/navigationlib.php |  6 ------
 message/lib.php       | 23 ++---------------------
 2 files changed, 2 insertions(+), 27 deletions(-)

diff --git a/lib/navigationlib.php b/lib/navigationlib.php
index 588bb99aada97..2f6c61006e4de 100644
--- a/lib/navigationlib.php
+++ b/lib/navigationlib.php
@@ -2334,9 +2334,6 @@ protected function load_for_user($user=null, $forceforcontext=false) {
                 if ($USER->id != $user->id) {
                     $messageargs['user2'] = $user->id;
                 }
-                if ($course->id != $SITE->id) {
-                    $messageargs['viewing'] = MESSAGE_VIEW_COURSE. $course->id;
-                }
                 $url = new moodle_url('/message/index.php', $messageargs);
                 $usernode->add(get_string('messages', 'message'), $url, self::TYPE_SETTING, null, 'messages');
             }
@@ -4640,9 +4637,6 @@ protected function generate_user_settings($courseid, $userid, $gstitle='usercurr
                 if ($USER->id != $user->id) {
                     $messageargs['user2'] = $user->id;
                 }
-                if ($course->id != $SITE->id) {
-                    $messageargs['viewing'] = MESSAGE_VIEW_COURSE. $course->id;
-                }
                 $url = new moodle_url('/message/index.php', $messageargs);
                 $dashboard->add(get_string('messages', 'message'), $url, self::TYPE_SETTING, null, 'messages');
             }
diff --git a/message/lib.php b/message/lib.php
index f3820c39ceaa5..d79fdc7042111 100644
--- a/message/lib.php
+++ b/message/lib.php
@@ -24,31 +24,12 @@
 
 require_once($CFG->libdir.'/eventslib.php');
 
-define ('MESSAGE_SHORTLENGTH', 300);
+define('MESSAGE_SHORTLENGTH', 300);
 
-define ('MESSAGE_DISCUSSION_WIDTH',600);
-define ('MESSAGE_DISCUSSION_HEIGHT',500);
-
-define ('MESSAGE_SHORTVIEW_LIMIT', 8);//the maximum number of messages to show on the short message history
-
-define('MESSAGE_HISTORY_SHORT',0);
-define('MESSAGE_HISTORY_ALL',1);
-
-define('MESSAGE_VIEW_UNREAD_MESSAGES','unread');
-define('MESSAGE_VIEW_RECENT_CONVERSATIONS','recentconversations');
-define('MESSAGE_VIEW_RECENT_NOTIFICATIONS','recentnotifications');
-define('MESSAGE_VIEW_CONTACTS','contacts');
-define('MESSAGE_VIEW_BLOCKED','blockedusers');
-define('MESSAGE_VIEW_COURSE','course_');
-define('MESSAGE_VIEW_SEARCH','search');
+define('MESSAGE_HISTORY_ALL', 1);
 
 define('MESSAGE_SEARCH_MAX_RESULTS', 200);
 
-define('MESSAGE_CONTACTS_PER_PAGE',10);
-define('MESSAGE_MAX_COURSE_NAME_LENGTH', 30);
-
-define('MESSAGE_UNREAD', 'unread');
-define('MESSAGE_READ', 'read');
 define('MESSAGE_TYPE_NOTIFICATION', 'notification');
 define('MESSAGE_TYPE_MESSAGE', 'message');