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cluster: Add some docs, improve cluster.isWorker()

Fixes #1949.
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tj authored and ry committed Oct 26, 2011
1 parent c5d5401 commit 528c28587f11b64616ffa22b5cf3f53bea831792
Showing with 53 additions and 27 deletions.
  1. +51 −19 doc/api/cluster.markdown
  2. +2 −8 lib/cluster.js
@@ -7,25 +7,57 @@ processes to handle the load.
The cluster module allows you to easily create a network of processes all
which share server ports.

var cluster = require('cluster');
var http = require('http');

if (!cluster.isWorker()) {
// Start the master process, fork workers.
cluster.startMaster({ workers: 2 });
} else {
// Worker processes have a http server.
http.Server(function(req, res) {
res.writeHead(200);
res.end("hello world\n");
}).listen(8000);
}

If we start it like this

% node cluster server.js
Detected 2 cpus
var cluster = require('cluster');
var http = require('http');

if (cluster.isMaster) {
// Start the master process, fork workers.
cluster.startMaster({ workers: 2 });
} else {
// Worker processes have a http server.
http.Server(function(req, res) {
res.writeHead(200);
res.end("hello world\n");
}).listen(8000);
}

Running node will now share port 8000 between the workers:

% node server.js
Worker 2438 online
Worker 2437 online

Node will automatically share port 8000 between the multiple instances.
### exports.startMaster([options])

Spawns the initial worker processes, one per CPU by default.

The following options are supported:

- `filename`: script to execute in the worker process, defaults to
`process.argv[1]`
- `args`: worker program arguments, defaulting to `process.argv.slice(2)`
- `workers`: the number of workers, defaulting to `os.cpus().length`

### exports.spawnWorker([options])

Spawn a new worker process. This is called within `cluster.startMaster()`,
however it is useful to implement worker resuscitation as described below
in the "Common patterns" section.

The `options` available are identical to `cluster.startMaster()`.

## Common patterns

## Worker resuscitation

The following is an example of how you may implement worker resuscitation,
spawning a new worker process when another exits.

if (cluster.isMaster) {
cluster.startMaster();
process.on('SIGCHLD', function(){
console.log('worker killed');
cluster.spawnWorker();
});
}

@@ -47,14 +47,8 @@ var workerId = 0;
var queryIds = 0;
var queryCallbacks = {};



// Used to check if this process is a worker or not.
// Returns boolean.
exports.isWorker = function() {
return 'NODE_WORKER_ID' in process.env;
};

exports.isWorker = 'NODE_WORKER_ID' in process.env;
exports.isMaster = ! exports.isWorker;

// Call this from the master process. It will start child workers.
//

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