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Streaming.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Espresso Framework</title>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<script src="javascripts/jquery.js" type="text/javascript"></script>
<link href="javascripts/bootstrap/css/bootstrap.min.css" rel="stylesheet" />
<link href="javascripts/bootstrap/css/bootstrap-responsive.min.css" rel="stylesheet" />
<script src="javascripts/bootstrap/js/bootstrap.min.js" type="text/javascript"></script>
<link href="javascripts/google-code-prettify/prettify.css" type="text/css" rel="stylesheet" />
<script src="javascripts/google-code-prettify/prettify.js" type="text/javascript"></script>
<link href="stylesheets/master.css" type="text/css" rel="stylesheet" />
</head>
<body>
<div class="container">
<div class="row">
<div class="span2">
<a href="index.html">
<img src="images/logo.png" class="pull-right logo" /></a>
</div>
<div class="span6">
<h1>
<a href="index.html">
Espresso Framework</a>
</h1>
<h4>
Scalable Web Framework aimed at Speed and Simplicity
</h4>
</div>
<div class="span pull-right">
<div class="row">
<div class="span">
<h4>
<a href="presentation.html">
Official Presentation</a>
</h4>
<h4 style="white-space: nowrap;">
<a href="Events.html">
Events</a> |
<a href="CHANGELOG.html">
Change Log</a>
</h4>
</div>
</div>
</div>
</div>
<hr/>
<div class="row" style="text-align: center;">
<div class="btn-toolbar">
<div class="btn-group" style="text-align: left; margin: 5px;">
<a href="Intro.html" class="btn">
Intro</a>
<button class="btn dropdown-toggle" data-toggle="dropdown">
<span class="caret"></span>
</button>
<ul class="dropdown-menu">
<li>
<a href="Intro.html#actions">
Actions</a>
</li>
<li>
<a href="Intro.html#controllers">
Controllers</a>
</li>
<li>
<a href="Intro.html#slices">
Slices</a>
</li>
<li>
<a href="Intro.html#mvc-">
MVC?</a>
</li>
<li>
<a href="Intro.html#models-">
Models?</a>
</li>
</ul>
</div>
<div class="btn-group" style="text-align: left; margin: 5px;">
<a href="Routing.html" class="btn">
Routing</a>
<button class="btn dropdown-toggle" data-toggle="dropdown">
<span class="caret"></span>
</button>
<ul class="dropdown-menu">
<li>
<a href="Routing.html#base-url">
Base URL</a>
</li>
<li>
<a href="Routing.html#canonicals">
Canonicals</a>
</li>
<li>
<a href="Routing.html#actions">
Actions</a>
</li>
<li>
<a href="Routing.html#action-mapping">
Action Mapping</a>
</li>
<li>
<a href="Routing.html#action-aliases">
Action Aliases</a>
</li>
<li>
<a href="Routing.html#parametrization">
Parametrization</a>
</li>
<li>
<a href="Routing.html#format">
Format</a>
</li>
<li>
<a href="Routing.html#restful-actions">
RESTful Actions</a>
</li>
<li>
<a href="Routing.html#rewriter">
Rewriter</a>
</li>
</ul>
</div>
<div class="btn-group" style="text-align: left; margin: 5px;">
<a href="Setup.html" class="btn">
Setup</a>
<button class="btn dropdown-toggle" data-toggle="dropdown">
<span class="caret"></span>
</button>
<ul class="dropdown-menu">
<li>
<a href="Setup.html#global-setup">
Global Setup</a>
</li>
<li>
<a href="Setup.html#setup-by-name">
Setup by Name</a>
</li>
<li>
<a href="Setup.html#setup-by-format">
Setup by Format</a>
</li>
<li>
<a href="Setup.html#remote-setup">
Remote Setup</a>
</li>
</ul>
</div>
<div class="btn-group" style="text-align: left; margin: 5px;">
<a href="Workflow.html" class="btn">
Workflow</a>
<button class="btn dropdown-toggle" data-toggle="dropdown">
<span class="caret"></span>
</button>
<ul class="dropdown-menu">
<li>
<a href="Workflow.html#route">
Route</a>
</li>
<li>
<a href="Workflow.html#params">
Params</a>
</li>
<li>
<a href="Workflow.html#passing-control">
Passing Control</a>
</li>
<li>
<a href="Workflow.html#fetching-body">
Fetching Body</a>
</li>
<li>
<a href="Workflow.html#halt">
Halt</a>
</li>
<li>
<a href="Workflow.html#redirect">
Redirect</a>
</li>
<li>
<a href="Workflow.html#reload">
Reload</a>
</li>
<li>
<a href="Workflow.html#error-handlers">
Error Handlers</a>
</li>
<li>
<a href="Workflow.html#hooks">
Hooks</a>
</li>
<li>
<a href="Workflow.html#authorization">
Authorization</a>
</li>
<li>
<a href="Workflow.html#sessions">
Sessions</a>
</li>
<li>
<a href="Workflow.html#flash">
Flash</a>
</li>
<li>
<a href="Workflow.html#cookies">
Cookies</a>
</li>
<li>
<a href="Workflow.html#content-type">
Content Type</a>
</li>
<li>
<a href="Workflow.html#charset">
Charset</a>
</li>
<li>
<a href="Workflow.html#cache-control">
Cache Control</a>
</li>
<li>
<a href="Workflow.html#expires">
Expires</a>
</li>
<li>
<a href="Workflow.html#last-modified">
Last Modified</a>
</li>
<li>
<a href="Workflow.html#accepted-content-type">
Accepted Content Type</a>
</li>
<li>
<a href="Workflow.html#cache-manager">
Cache Manager</a>
</li>
<li>
<a href="Workflow.html#send-file">
Send File</a>
</li>
<li>
<a href="Workflow.html#send-files">
Send Files</a>
</li>
<li>
<a href="Workflow.html#attachment">
Attachment</a>
</li>
<li>
<a href="Workflow.html#headers">
Headers</a>
</li>
</ul>
</div>
<div class="btn-group" style="text-align: left; margin: 5px;">
<a href="ViewAPI.html" class="btn">
View API</a>
<button class="btn dropdown-toggle" data-toggle="dropdown">
<span class="caret"></span>
</button>
<ul class="dropdown-menu">
<li>
<a href="ViewAPI.html#engine">
Engine</a>
</li>
<li>
<a href="ViewAPI.html#extension">
Extension</a>
</li>
<li>
<a href="ViewAPI.html#templates-path">
Templates Path</a>
</li>
<li>
<a href="ViewAPI.html#layouts-path">
Layouts Path</a>
</li>
<li>
<a href="ViewAPI.html#layout">
Layout</a>
</li>
<li>
<a href="ViewAPI.html#rendering-templates">
Rendering Templates</a>
</li>
<li>
<a href="ViewAPI.html#rendering-layouts">
Rendering Layouts</a>
</li>
<li>
<a href="ViewAPI.html#ad-hoc-rendering">
Ad hoc Rendering</a>
</li>
<li>
<a href="ViewAPI.html#path-resolver">
Path Resolver</a>
</li>
<li>
<a href="ViewAPI.html#templates-compilation">
Templates Compilation</a>
</li>
</ul>
</div>
<div class="btn-group" style="text-align: left; margin: 5px;">
<a href="Streaming.html" class="btn">
Streaming</a>
<button class="btn dropdown-toggle" data-toggle="dropdown">
<span class="caret"></span>
</button>
<ul class="dropdown-menu">
<li>
<a href="Streaming.html#server-sent-events">
Server-Sent Events</a>
</li>
<li>
<a href="Streaming.html#websockets">
WebSockets</a>
</li>
<li>
<a href="Streaming.html#chunked-responses">
Chunked Responses</a>
</li>
</ul>
</div>
<div class="btn-group" style="text-align: left; margin: 5px;">
<a href="Assets.html" class="btn">
Assets</a>
<button class="btn dropdown-toggle" data-toggle="dropdown">
<span class="caret"></span>
</button>
<ul class="dropdown-menu">
<li>
<a href="Assets.html#tag-helpers">
Tag Helpers</a>
</li>
<li>
<a href="Assets.html#assets-mapper">
Assets Mapper</a>
</li>
</ul>
</div>
<div class="btn-group" style="text-align: left; margin: 5px;">
<a href="CRUD.html" class="btn">
CRUD</a>
<button class="btn dropdown-toggle" data-toggle="dropdown">
<span class="caret"></span>
</button>
<ul class="dropdown-menu">
<li>
<a href="CRUD.html#intro">
Intro</a>
</li>
<li>
<a href="CRUD.html#resource">
Resource</a>
</li>
<li>
<a href="CRUD.html#excluded-params">
Excluded Params</a>
</li>
<li>
<a href="CRUD.html#root">
Root</a>
</li>
<li>
<a href="CRUD.html#response">
Response</a>
</li>
<li>
<a href="CRUD.html#error-handler">
Error Handler</a>
</li>
<li>
<a href="CRUD.html#access-restriction">
Access Restriction</a>
</li>
</ul>
</div>
<div class="btn-group" style="text-align: left; margin: 5px;">
<a href="Deploy.html" class="btn">
Deploy</a>
<button class="btn dropdown-toggle" data-toggle="dropdown">
<span class="caret"></span>
</button>
<ul class="dropdown-menu">
<li>
<a href="Deploy.html#controllers">
Controllers</a>
</li>
<li>
<a href="Deploy.html#slices">
Slices</a>
</li>
<li>
<a href="Deploy.html#roots">
Roots</a>
</li>
<li>
<a href="Deploy.html#run">
Run</a>
</li>
<li>
<a href="Deploy.html#config-ru">
config.ru</a>
</li>
</ul>
</div>
</div>
</div>
<hr/>
<h4>Note: Streaming in Espresso is working only with <a href="https://github.com/celluloid/reel">Reel</a> web server of version 0.3 and up</h4>
<h2 id='server-sent-events'><a href='#server-sent-events'>Server-Sent Events</a></h2>
<p>As easy as:</p>
<pre lang="html">
<script type="text/javascript">
var evs = new EventSource('/subscribe');
evs.onmessage = function(e) {
$('#wall').html( e.data );
}
</script>
</pre>
<pre>
class App < E
map '/'
def subscribe
event_stream do |stream|
stream.data 'some string' # will set #wall's HTML to 'some string'
end
end
end
</pre>
<p>Other stream helpers:</p>
<ul>
<li>event</li>
<li>retry</li>
<li>id</li>
</ul>
<pre lang="html">
<script type="text/javascript">
var evs = new EventSource('/subscribe');
evs.addEventListener('time', function(e) {
$('#time').html( e.data );
}, false);
</script>
</pre>
<pre>
def subscribe
event_stream do |stream|
stream.event 'time'
stream.data Time.now.to_s # will set #time's HTML to current time
end
end
</pre>
<p>Writing to stream directly:</p>
<pre>
def some_action
event_stream do |stream|
stream << "event: time\n"
stream << "data: #{Time.now}\n\n"
end
end
</pre>
<p>Using it without <code>event_stream</code> helper:</p>
<pre>
def some_action
response.body = Reel::EventStream.new do |stream|
# write to stream directly or via stream helpers
end
end
</pre>
<p><strong>[ <a href="#">contents ↑</a> ]</strong></p>
<h2 id='websockets'><a href='#websockets'>WebSockets</a></h2>
<p>As easy as:</p>
<pre lang="html">
<script type="text/javascript">
ws = new WebSocket('ws://host:port/subscribe');
ws.onmessage = function(e) {
$('#wall').html( e.data );
}
</script>
<input type="text" id="message">
<input type="button" onClick="ws.send( $('#message').val() );" value="send message">
</pre>
<pre>
def subscribe
if socket = websocket?
socket << 'Welcome to the wall'
socket.on_message do |msg|
# will set #wall's HTML to current time + received message
socket << "#{Time.now}: #{msg}"
end
socket.on_error { socket.close unless socket.closed? }
socket.read_interval 1 # reading from socket every 1 second
end
end
</pre>
<p><strong>[ <a href="#">contents ↑</a> ]</strong></p>
<h2 id='chunked-responses'><a href='#chunked-responses'>Chunked Responses</a></h2>
<p><strong>From W3.org:</strong></p>
<blockquote>
The chunked encoding modifies the body of a message in order to transfer it as a series of chunks,
each with its own size indicator, followed by an OPTIONAL trailer containing entity-header fields.
This allows dynamically produced content to be transferred along with the information necessary
for the recipient to verify that it has received the full message.
</blockquote>
<p>So, this is useful when your body is not yet ready in full and you want to start sending it by chunks.</p>
<p>You should not worry about data size/encoding, everything is done under-the-hood by Espresso.</p>
<p>Here is an example that will release the response instantly and then send body by chunks:</p>
<pre>
def some_heavy_action
chunked_stream do |socket|
ExtractDataFromDBOrSomePresumablySlowAPI.each do |data|
socket << data.to_s
end
socket.finish # close it, otherwise the browser will waiting for data forever
end
end
</pre>
<p>Please make sure to do <code>socket.finish</code> after all your data sent.</p>
<hr/>
<footer class="footer well">
<div class="row">
<div class="span4">
<p>
License: MIT
</p>
<p>
Author: Silviu Rusu
</p>
<p>
Source Code:
<a href="https://github.com/espresso/espresso">
https://github.com/espresso/espresso</a>
</p>
</div>
<div class="span6 pull-right">
<p>
Issues/Bugs:
<a href="https://github.com/espresso/espresso/issues">
https://github.com/espresso/espresso/issues</a>
</p>
<p>
<strong>Contributors are very Welcome!</strong>
</p>
<p>
IRC channel: #espressorb on irc.freenode.net
</p>
</div>
</div>
</footer>
</div>
<a href="https://github.com/espresso/espresso"><img style="position: absolute; top: 0; right: 0; border: 0;" src="https://s3.amazonaws.com/github/ribbons/forkme_right_gray_6d6d6d.png" alt="Fork me on GitHub"></a>
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