Merge ead4de4 into 9c0f1c6

docs/middleware/actions.md

@@ -149,9 +149,13 @@ This action has these additional `context` properties:
 
 > The query's projection [fields]({{ site.baseurl }}{% link api/backend.md %}#addprojection)
 
-`channel` -- string
+`channel` -- string (deprecated)
 
-> The [Pub/Sub]({{ site.baseurl }}{% link adapters/pub-sub.md %}) channel the query will subscribe to. Defaults to its collection channel.
+> This property is deprecated use `channels` instead. The [Pub/Sub]({{ site.baseurl }}{% link adapters/pub-sub.md %}) channels the query will subscribe to. Defaults to its collection channel.
+
+`channels` -- string[]
+
+> The [Pub/Sub]({{ site.baseurl }}{% link adapters/pub-sub.md %}) channels the query will subscribe to. Defaults to its collection channel.
 
 `query` -- Object
 

docs/queries.md

@@ -160,7 +160,7 @@ backend.use('commit', (context, next) => {
 
 backend.use('query', (context, next) => {
   // Set our query to only listen for changes on our user-specific channel
-  context.channel = userChannel(context)
+  context.channels = [userChannel(context)]
   next()
 })
 

lib/backend.js

@@ -661,25 +661,62 @@ Backend.prototype.querySubscribe = function(agent, index, query, options, callba
         'DB does not support subscribe'
       ));
     }
-    backend.pubsub.subscribe(request.channel, function(err, stream) {
-      if (err) return callback(err);
+
+    var channels = request.channels;
+
+    if (request.channel) {
+      logger.warn(
+        '[DEPRECATED] "query" middleware\'s context.channel is deprecated, use context.channels instead.' +
+        'Read more: https://share.github.io/sharedb/middleware/actions#query'
+      );
+      channels = [request.channel];
+    }
+
+    if (!channels || !channels.length) {
+      return callback(new ShareDBError(ERROR_CODE.ERR_QUERY_CHANNEL_MISSING, 'Required minimum one query channel.'));
+    }
+
+    var streams = [];
+
+    function destroyStreams() {
+      streams.forEach(function(stream) {
+        stream.destroy();
+      });
+    }
+
+    function createQueryEmitter() {
       if (options.ids) {
-        var queryEmitter = new QueryEmitter(request, stream, options.ids);
+        var queryEmitter = new QueryEmitter(request, streams, options.ids);
         backend.emit('timing', 'querySubscribe.reconnect', Date.now() - start, request);
         callback(null, queryEmitter);
         return;
       }
       // Issue query on db to get our initial results
       backend._query(agent, request, function(err, snapshots, extra) {
         if (err) {
-          stream.destroy();
+          destroyStreams();
           return callback(err);
         }
         var ids = pluckIds(snapshots);
-        var queryEmitter = new QueryEmitter(request, stream, ids, extra);
+        var queryEmitter = new QueryEmitter(request, streams, ids, extra);
         backend.emit('timing', 'querySubscribe.initial', Date.now() - start, request);
         callback(null, queryEmitter, snapshots, extra);
       });
+    }
+
+    channels.forEach(function(channel) {
+      backend.pubsub.subscribe(channel, function(err, stream) {
+        if (err) {
+          destroyStreams();
+          return callback(err);
+        }
+        streams.push(stream);
+
+        var subscribedToAllChannels = streams.length === channels.length;
+        if (subscribedToAllChannels) {
+          createQueryEmitter();
+        }
+      });
     });
   });
 };
@@ -693,7 +730,7 @@ Backend.prototype._triggerQuery = function(agent, index, query, options, callbac
     collection: collection,
     projection: projection,
     fields: fields,
-    channel: this.getCollectionChannel(collection),
+    channels: [this.getCollectionChannel(collection)],
     query: query,
     options: options,
     db: null,

lib/error.js

@@ -45,6 +45,7 @@ ShareDBError.CODES = {
   ERR_OT_OP_NOT_PROVIDED: 'ERR_OT_OP_NOT_PROVIDED',
   ERR_PRESENCE_TRANSFORM_FAILED: 'ERR_PRESENCE_TRANSFORM_FAILED',
   ERR_PROTOCOL_VERSION_NOT_SUPPORTED: 'ERR_PROTOCOL_VERSION_NOT_SUPPORTED',
+  ERR_QUERY_CHANNEL_MISSING: 'ERR_QUERY_CHANNEL_MISSING',
   ERR_QUERY_EMITTER_LISTENER_NOT_ASSIGNED: 'ERR_QUERY_EMITTER_LISTENER_NOT_ASSIGNED',
   /**
    * A special error that a "readSnapshots" middleware implementation can use to indicate that it

lib/query-emitter.js

@@ -5,7 +5,7 @@ var util = require('./util');
 
 var ERROR_CODE = ShareDBError.CODES;
 
-function QueryEmitter(request, stream, ids, extra) {
+function QueryEmitter(request, streams, ids, extra) {
   this.backend = request.backend;
   this.agent = request.agent;
   this.db = request.db;
@@ -15,18 +15,20 @@ function QueryEmitter(request, stream, ids, extra) {
   this.fields = request.fields;
   this.options = request.options;
   this.snapshotProjection = request.snapshotProjection;
-  this.stream = stream;
+  this.streams = streams;
   this.ids = ids;
   this.extra = extra;
 
   this.skipPoll = this.options.skipPoll || util.doNothing;
   this.canPollDoc = this.db.canPollDoc(this.collection, this.query);
   this.pollDebounce =
     (typeof this.options.pollDebounce === 'number') ? this.options.pollDebounce :
-      (typeof this.db.pollDebounce === 'number') ? this.db.pollDebounce : 0;
+      (typeof this.db.pollDebounce === 'number') ? this.db.pollDebounce :
+        streams.length > 1 ? 1000 : 0;
   this.pollInterval =
     (typeof this.options.pollInterval === 'number') ? this.options.pollInterval :
-      (typeof this.db.pollInterval === 'number') ? this.db.pollInterval : 0;
+      (typeof this.db.pollInterval === 'number') ? this.db.pollInterval :
+        streams.length > 1 ? 1000 : 0;
 
   this._polling = false;
   this._pendingPoll = null;
@@ -41,23 +43,32 @@ QueryEmitter.prototype._open = function() {
   this._defaultCallback = function(err) {
     if (err) emitter.onError(err);
   };
-  emitter.stream.on('data', function(data) {
-    if (data.error) {
-      return emitter.onError(data.error);
-    }
-    emitter._update(data);
-  });
-  emitter.stream.on('end', function() {
-    emitter.destroy();
+
+  emitter.streams.forEach(function(stream) {
+    stream.on('data', function(data) {
+      if (data.error) {
+        return emitter.onError(data.error);
+      }
+      emitter._update(data);
+    });
+    stream.on('end', function() {
+      emitter.destroy();
+    });
   });
+
   // Make sure we start polling if pollInterval is being used
   this._flushPoll();
 };
 
 QueryEmitter.prototype.destroy = function() {
   clearTimeout(this._pollDebounceId);
   clearTimeout(this._pollIntervalId);
-  this.stream.destroy();
+
+  var stream;
+
+  while (stream = this.streams.pop()) {
+    stream.destroy();
+  }
 };
 
 QueryEmitter.prototype._emitTiming = function(action, start) {
@@ -140,8 +151,8 @@ QueryEmitter.prototype._flushPoll = function() {
   if (this._pendingPoll) {
     this.queryPoll();
 
-  // If a pollInterval is specified, poll if the query doesn't get polled in
-  // the time of the interval
+    // If a pollInterval is specified, poll if the query doesn't get polled in
+    // the time of the interval
   } else if (this.pollInterval) {
     var emitter = this;
     this._pollIntervalId = setTimeout(function() {
@@ -301,14 +312,14 @@ QueryEmitter.prototype.queryPollDoc = function(id, callback) {
 // all messages are received and applied in order, so it is critical that none
 // are dropped.
 QueryEmitter.prototype.onError =
-QueryEmitter.prototype.onDiff =
-QueryEmitter.prototype.onExtra =
-QueryEmitter.prototype.onOp = function() {
-  throw new ShareDBError(
-    ERROR_CODE.ERR_QUERY_EMITTER_LISTENER_NOT_ASSIGNED,
-    'Required QueryEmitter listener not assigned'
-  );
-};
+  QueryEmitter.prototype.onDiff =
+  QueryEmitter.prototype.onExtra =
+  QueryEmitter.prototype.onOp = function() {
+    throw new ShareDBError(
+      ERROR_CODE.ERR_QUERY_EMITTER_LISTENER_NOT_ASSIGNED,
+      'Required QueryEmitter listener not assigned'
+    );
+  };
 
 function getInserted(diff) {
   var inserted = [];