node package manager

socketcluster

SocketCluster - A Highly parallelized WebSocket server cluster to make the most of multi-core machines/instances.

SocketCluster

Complete documentation available at: http://socketcluster.io/

22 July 2016 (v4.7.0)

  • Since the Node.js domain module is now deprecated, we have switched to using our own sc-domain module which uses Promises to capture async errors. The sc-domain module doesn't behave exactly like the Node.js domain module though; the main difference is that it does not capture unhandled + nested 'error' events (it only captures thrown errors including those thrown asynchronously). This means that you now have to be more careful about handling all your 'error' events - SC's default behavior for handling uncaught error events is to crash and respawn the affected process - This is the approach recommended by the Node.js core team.

16 January 2016 (v4.2.0)

  • The schedulingPolicy option (http://socketcluster.io/#!/docs/api-socketcluster) is now 'rr' by default (except on Windows) - After doing some stress testing on large 8-core Linux EC2 instances, the 'rr' policy turned out to be much better at distributing load across multiple CPU cores. The downside of the 'rr' policy is that all new connection fds pass through a central master process but that process turned out to be extremely efficient. It's not a perfect solution but it's much better than letting the Linux OS handle it.

05 January 2016 (v4.0.0)

  • Middleware functions used to have different arguments (depending on the middleware type); now they are all in the format function (req, next) {...}. The req object will have different properties depending on the middleware type. See addMiddleware() method here: http://socketcluster.io/#!/docs/api-scserver
  • When invoking socket.emit or socket.publish - When a callback was provided, it would emit an 'error' event on the socket if the operation failed. This is no longer the case - The callback will still receive the error as the first argument like it used to (assuming that there was an error), but it just won't be emitted as an 'error' event on the socket - It is considered an application error (not an SC error).
  • The 'notice' event was replaced with a 'warning' event - This is more consistent with the convention used in most other frameworks.
  • You can now pass custom error objects to the next(err) callback inside middleware functions; this is now recommended instead of plain strings. The err object you provide can inherit from the Error object (but this isn't necessary). It is recommended that whatever object you provide has a name and a message property; you can also add custom properties to your error object and the client will receive those as rehydrated Error objects. Note that this is a non-breaking change - You can still pass a string as err and it won't break anything.
  • On the server-side, the socket.removeAuthToken() method was replaced by socket.deauthenticate().

This release introduces many other non-breaking changes.

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 worker and broker 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.

  • Jonathan Gros-Dubois
  • Nelson Zheng
  • wactbprot (nData)
  • epappas (nData)
  • Gabriel Muller

There are two ways to install SocketCluster.

Setup the socketcluster command:

npm install -g socketcluster

OR

sudo npm install -g socketcluster

Then

socketcluster create myapp

Once it's installed, go to your new myapp/ directory and launch with:

node server

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 = new SocketCluster({
  workers: 3,
  brokers: 3,
  port: 8000,
  appName: 'myapp',
  workerController: 'worker.js',
  protocol: 'https',
  protocolOptions: {
    key: fs.readFileSync(__dirname + '/keys/enc_key.pem', 'utf8'),
    cert: fs.readFileSync(__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

You can create an app on top of SocketCluster's docker image. The SC container can be run standalone or as a base image for your own container.

The official SocketCluster container on DockerHub is here: https://hub.docker.com/r/socketcluster/socketcluster/

The Dockerfile for the base image is here: https://github.com/SocketCluster/socketcluster/blob/master/sample/Dockerfile

To use the SocketCluster container as your base image, your app's Dockerfile might look like this:

FROM socketcluster/socketcluster
MAINTAINER John Smith
 
LABEL version="1.0.0"
LABEL description="Custom app based on SocketCluster"
 
WORKDIR /usr/src/
COPY . /usr/src/
 
RUN npm install
 
EXPOSE 8000
 
CMD ["npm", "start"]
 

Then you can just build your container using:

docker build -t my-socketcluster-app:v1.0.0 .

Note that there are more ways to run SocketCluster with Docker. You can also mount your own volumes and point to custom worker.js and broker.js files which are inside those volumes using environment variables. You can see the environment variables which are used by SocketCluster here: https://github.com/SocketCluster/socketcluster/blob/master/sample/server.js

Docker volumes allow you to sneak your own directories (containing your own worker.js and broker.js source files) into the SocketCluster container without having to rebuild the image (good for development). Read this section on volumes to get an idea of how they work with Docker: https://docs.docker.com/engine/userguide/containers/dockervolumes/

Note that if you want to attach any volumes to your SocketCluster container, you should mount them to the /usr/src/ path (inside the container) - That's the root directory from which SC loads user-defined source code.

For example, if you wanted to quickly run SocketCluster with your own workerController file (worker.js), you could just put your worker.js file inside a /home/my-username/controllers/ directory (on your host system) and then bundle it into the container as a volume by running a command like this (example):

docker run -d -v /home/my-username/controllers/:/usr/src/controllers/ -e "SOCKETCLUSTER_WORKER_CONTROLLER=/usr/src/controllers/worker.js" socketcluster/socketcluster

To summarize:

  • The -d flag just tells Docker to run the container in the background.
  • The -v flag tells docker to mount the /home/my-username/controllers/ directory (which is on your host machine) and map it to the /usr/src/controllers/ (inside the SocketCluster container).
  • The -e flag allows you to define custom environment variables. Here we are just using the SOCKETCLUSTER_WORKER_CONTROLLER env var to tell SocketCluster to use the worker.js file which is inside the volume which we just mounted to the container at path /usr/src/controllers/.
  • The final argument socketcluster/socketcluster is the Docker image.
  • More integration test cases needed
  • Unit tests
  • Efficiency/speed - faster is better!
  • Suggestions?

To contribute; clone this repo, then cd inside it and then run npm install to install all dependencies.

(The MIT License)

Copyright (c) 2013-2016 SocketCluster.io

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.