socket.io-mongodb

A MongoDB Adapter for socket.io, based on socket.io-redis.

This adapter:

Implements the full socket.io-adapter, including rooms and room deletion
Supports SSL connections to the database
Leverages mubsub

How to use

var io = require('socket.io')(3000),
    mongoAdapter = require('socket.io-mongodb');
 
io.adapter(mongoAdapter('mongodb://localhost:27017/socket-io'));

By running socket.io with the socket.io-mongodb adapter you can run multiple socket.io instances in different processes or servers that can all broadcast and emit events to and from each other.

If you need to emit events to socket.io instances from a non-socket.io process, you should use socket.io-emitter.

API

adapter(uri[, opts])

The first argument, uri, expects a MongoDB connection string (i.e. mongodb://localhost:27017/socket-io). The options argument is explained below.

var io = require('socket.io')(3000),
    mongoAdapter = require('socket.io-mongodb'),
    adapter;
 
adapter = mongoAdapter('mongodb://localhost:27017/socket-io', {
    prefix: 'myprefix',
    collectionName: 'mypubsub'
});
 
io.adapter(adapter);

adapter(opts)

The options described here can be passed in as the first argument, or as the second argument, when the first argument is your MongoDB connection string.

uri (required string or object): a MongoDB connection string, or a URI object that can be parsed by mongodb-uri
prefix (optional string): a prefix to be used when publishing events (default is socket-io)
collectionName (optional string): the name of the MongoDB collection that mubsub should create/use (default is pubsub). This is ignored if the mongoClient or pubsubClient properties are defined.
mongoClient (optional instance of MongoDB node driver): the MongoDB driver to use. This is ignored if the pubsubClient is defined. @alsoSee Existing database connection
pubsubClient (optional instance of mubsub): the mubsub client to use. This can be replaced by another library that implements the channel, channel.subscribe, and channel.publish interfaces. @alsoSee Custom client
channel (optional mubsub channel): the mubsub channel to use. This is only respected if the pubsubClient is also defined. @alsoSee Custom client
messageEncoder (optional object): an object with encode and decode functions, to be used when encoding/decoding pubsub messages. The default uses JSON.stringify and JSON.parse to encode and decode, respectively. @alsoSee: Overriding the messageEncoder

var io = require('socket.io')(3000),
    mongoAdapter = require('socket.io-mongodb'),
    adapter;
    //fs = require('fs'),
    //sslCA = [fs.readFileSync(__dirname + '/mySSLCA.pem')]; // you may want to switch this to `readFile` so as not to block - it's just here for example
 
adapter = mongoAdapter({
    "uri": {
        "hosts": [
            {
                "host": "db01.mysite.com",
                "port": 27017
            },
            {
                "host": "db02.mysite.com",
                "port": 27017
            }
        ],
        "username": "admin",
        "password": "password",
        "database": "socket-io",
        "options": {
            "authSource": "admin",
            "replicaSet": "myreplset",
            "ssl": true
        }
    },
    "server": {
        //"sslCA": sslCA
        "sslValidate": false
    },
    "replSet": {
        //"sslCA": sslCA
        "sslValidate": false
    }
    "prefix": 'myprefix',
    "collectionName": 'mypubsub'
});
 
io.adapter(adapter);

The options that are described here are passed through to mubsub, which in turn passes them to the native MongoDB driver. So you can include options that are relevant to those libraries. Also, if you pass an object in as the uri property, it is processed by mongodb-uri.

Client error handling

This adapter exposes the pubsubClient property (mubsub), as well as the channel that was created. You can bind to events on each of these resources:

var io = require('socket.io')(3000),
    mongoAdapter = require('socket.io-mongodb'),
    adapter = mongoAdapter('mongodb://localhost:27017/socket-io');
 
io.adapter(adapter);
adapter.pubsubClient.on('error', console.error);
adapter.channel.on('error', console.error);

Custom client

You can inject your own pubsub client (i.e. if you already have an instance of mubsub you wish to use), using the pubsubClient property of the options.

var io = require('socket.io')(3000),
    mubsub = require('mubsub'),
    mongoAdapter = require('socket.io-mongodb'),
    client;
 
client = mubsub('mongodb://localhost:27017/io-example');
channel = client.channel('test');   // the channel is optional
 
io.adapter(mongoAdapter({
    pubsubClient: mubsub,
    channel: channel                // optional
}));

Existing database connection

You can inject an existing database connection, if you are not injecting the pubsubClient.

var io = require('socket.io')(3000),
    MongoClient = require('mongodb').MongoClient,
    mongoAdapter = require('socket.io-mongodb'),
    client;
 
MongoClient.connect('mongodb://localhost:27017/io-example', function(err, db) {
    io.adapter(mongoAdapter({
        mongoClient: db
    }));
});

The MongoClient is exposed as db on the adapter, so you can leverage it if you need to: myAdapter.db

Overriding the messageEncoder

If you don't want or need to be able to read the message data in the database, you may benefit from overriding the messageEncoder. The following example uses msgpack-js to encode/decode the message data.

var io = require('socket.io')(3000),
    mongoAdapter = require('socket.io-mongodb'),
    msgpack = require('msgpack-js');
 
io.adapter(mongoAdapter({
    uri: 'mongodb://localhost:27017/socket-io',
    messageEncoder: {
        encode: function (data) {
            return msgpack.encode(data);
        },
        decode: function (data) {
            return msgpack.decode(data.buffer);
        }
    }
}));

Protocol

The socket.io-mongodb adapter broadcasts and receives messages on particularly named channels. For global broadcasts the channel name is:

prefix + '#' + namespace + '#'

In broadcasting to a single room the channel name is:

prefix + '#' + namespace + '#' + room + '#'

prefix: a prefix to be used when publishing events (default is socket-io). You can change this by setting the prefix value in the constructor options
namespace: see https://github.com/socketio/socket.io#namespace.
room : used if targeting a specific room.

License

MIT