SocketCluster - A Highly parallelized WebSocket server cluster to make the most of multi-core machines/instances.
Complete documentation available at: http://socketcluster.io/
8 March 2015 (v2.0.2)
Updated http://socketcluster.io/ documentation.
In order to prepare SocketCluster for a smooth transition to version 2 over the next few years, some big changes were made to the API which will affect v1:
All these changes have been noted on the website.
SocketCluster v2 is now available for download. SC2 is our attempt to prepare SocketCluster for a WebSocket-enabled future, as such, SC2 is dropping support for all hacky long-polling fallback mechanisms which have been an architectural nightmare to manage in large deployments. The WebSocket adoption rate in the browser is currently estimated at 85%+ and so we would like SC to cater for forward-thinking developers/companies who are ready to make the bold move towards using pure WebSockets without fallback. The major trade-off of SC2 is reduced browser support in exchange for significantly increased speed and efficiency (including significantly lower network IO overheads).
Some cases where this trade-off may be worthwhile include:
V2 will be maintained and supported in parallel with v1 (fully backwards compatible). Version 1 will remain the official version until it makes sense to switch to v2 (based on feedback from the community).
Since v1 is still the official version, if you want to use v2, you will need to use a different npm command:
// Instead of 'npm install -g socketcluster'npm install -g sc2
Once installed, you should be able to invoke the 'sc2' command. The sc2 command has the exact same sub-commands as the v1 'socketcluster' command. For details, run:
The npm package name for the client is sc2-client.
SocketCluster is a fast, highly scalable HTTP + realtime server engine which lets you build multi-process realtime servers that make use of all CPU cores on a machine/instance. It removes the limitations of having to run your Node.js server as a single thread and makes your backend resilient by automatically recovering from worker crashes and aggregating errors into a central log.
Follow the project on Twitter: https://twitter.com/SocketCluster Subscribe for updates: http://socketcluster.launchrock.com/
SocketCluster has been tested for memory leaks. The last full memory profiling was done on SocketCluster v0.9.17 (Node.js v0.10.28) and included checks on load balancer, worker and store processes.
No memory leaks were detected when using the latest Node.js version. Note that leaks were found when using Node.js versions below v0.10.22 - This is probably the Node.js 'Walmart' memory leak - Not a SocketCluster issue.
There are two ways to install SocketCluster.
Setup the socketcluster command:
npm install -g socketcluster
sudo npm install -g socketcluster
socketcluster create myapp
Once it's installed, go to your new myapp/ directory and launch with:
Access at URL http://localhost:8000/
npm install socketcluster
You will also need to install the client separately which you can get using the following command:
npm install socketcluster-client
The socketcluster-client script is called socketcluster.js (located in the main socketcluster-client directory)
It is recommended that you use Node.js version >=0.10.22 due to memory leaks present in older versions.
In order to run SocketCluster over HTTPS, all you need to do is set the protocol to 'https' and provide your private key and certificate as a start option when you instantiate SocketCluster - Example:
var socketCluster =balancers: 1workers: 3stores: 3port: 8000appName: 'myapp'workerController: 'worker.js'protocol: 'https'protocolOptions:key: fsreadFileSync__dirname + '/keys/enc_key.pem' 'utf8'cert: fsreadFileSync__dirname + '/keys/cert.pem' 'utf8'passphrase: 'passphase4privkey';
The protocolOptions option is exactly the same as the one you pass to a standard Node HTTPS server: http://nodejs.org/api/https.html#https_https_createserver_options_requestlistener
Note that encryption/decryption in SocketCluster happens at the LoadBalancer level (SocketCluster launches one or more lightweight load balancers to distribute traffic evenly between your SocketCluster workers). LoadBalancers are responsible for encrypting/decrypting all network traffic. What this means is that your code (which is in the worker layer) will only ever deal with raw HTTP traffic.
Note that SC lets your store your authentication tokens anywhere you like; a database of your choice, Redis...
SocketCluster also lets you store session data using the socket.session object. This object gives you access to a cluster of in-memory stores called nData. nData is mostly used internally to allow workers to communicate with one another but it's also useful to store session-specific data. Note that if you want a user's auth token to span multiple sessions (so that user doesn't have to log in again after their session expires), then you might want to use a database to store the auth token instead of using the session object.
If you decide to use the socket.session object, you can invoke any of the methods documented here to store and retrieve session data: https://github.com/topcloud/ndata
For example, to authorize a user, you could check their login credentials and upon success, you could add an auth token to that session:
socketsessionset'isUserAuthorized' true callback;
Then, on subsequent events, you could check for that token before handling the event:
socketsessionget'isUserAuthorized'if value// Token is set, therefore this event is authorized;
The session object can also be accessed from the req object that you get from SocketCluster's HTTP server 'req' event (I.e. req.session).
SocketCluster provides two middleware lines for filtering out sockets and events.
MIDDLEWARE_HANDSHAKE middleware for filtering out sockets based on session data:
scServeraddMiddlewarescServerMIDDLEWARE_HANDSHAKEreqsessionget'isUserAuthorized'if valuenext;elsenext'Session ' + reqsessionid + ' was not authorized';;;
MIDDLEWARE_EVENT middleware for filtering out individual events:
scServeraddMiddlewarescServerMIDDLEWARE_EVENTif event == 'bla'next'bla event is not allowed for socket ' + socketid + ' on session ' + socketsessionid;elsenext;;
To contribute; clone this repo, then cd inside it and then run npm install to install all dependencies.
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