Elegant process clustering.
Elegant process clustering for node.js
- Controller <-> Child Event Transference
cohesion package is available for node through npm.
npm install cohesion
To ensure consistency, the following language will used throughout the documentation.
- Controller - the node script the is initially started and manages all child processes
The controller is the master process of a cohesion process cluster. Through it you can manage pre- and post- worker hooks, set number of workers, and listen for events.
To begin, construct a new worker by passing the path to the child script. An additional settings object can also be included to further modify a master behavior.
The most important event that the constructed master will emit is the
worker event; this
will be emitted for each new constructed worker. Events that are triggered on a worker process will
be emitted on child process, and visa-versa.
The following example demonstrates a simple counter which will round-robin a countdown between each spawned child.
/*** controller.js*/// create mastervar cohesion = require'cohesion'master = __dirname + '/child.js';// example countervar count = 30;// event for when each worker spawnsmasteron'worker'// emitted by child on startworkeron'ready'workeremit'calc' count;;// emitted by child after a calculationworkeron'next'if count > 0workeremit'count' count;count--;elseworkerstop;;;// event for when all workers have stoppedmasteron'stopped'console.log'all done';;// start all the workersmasterspawnWorkers;
The child is a small wrapper around the child-process api that turns each child process into a remote event listener and emitter.
The follow example demonstrates the child side of the previous counter example.
/*** child.js*/// mount child listenervar child = require'cohesion'child;// emitted by controllerchildon'count'setTimeoutconsole.log'pid %d - %d' childpid n;childemit'next';100;;// start the calculationschildemit'ready';
Provide a function that is be called before a worker is started. Function can be asyncronous and should be used to establish configuration. It will be called once before each worker is started, but not on restarts. Multiple calls will queue multiple before each functions that will be invoked in the order they are defined.
The following example uses harbor to assign a port to each worker.
var harbor = require'harbor'1227 1337n = 0;masterbeforeEachvar name = 'child-' + ++n;configname = name;harborclaimnameif err return doneerr;console.log'clamedconfig.port = port;done();});});
As you can see, config is a simple JSON object that will be serialized and provided to the child after startup. See the Child API for more information on how to access the config on the server side.
.beforeEach(), but queue functions to be invoked after a worker has completed it's
shutdown sequence. This occurs either when
worker.stop() is called or when a worker has reached
it's maximum restart attempts and the startup sequence is abandoned.
Interested in contributing? Fork to get started. Contact @logicalparadox if you are interested in being regular contributor.
- Jake Luer (@logicalparadox)
(The MIT License)
Copyright (c) 2012 Jake Luer firstname.lastname@example.org
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