node/lib/cluster.js

// Copyright Joyent, Inc. and other Node contributors.
//
// 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.

var assert = require('assert');
var fork = require('child_process').fork;
var net = require('net');
var EventEmitter = require('events').EventEmitter;

var cluster = module.exports = new EventEmitter();


var debug;
if (process.env.NODE_DEBUG && /cluster/.test(process.env.NODE_DEBUG)) {
  debug = function(x) {
    var prefix = process.pid + ',' +
        (process.env.NODE_WORKER_ID ? 'Worker' : 'Master');
    console.error(prefix, x);
  };
} else {
  debug = function() { };
}


// Used in the master:
var masterStarted = false;
var ids = 0;
var workers = [];
var servers = {};
var workerFilename;
var workerArgs;

// Used in the worker:
var workerId = 0;
var queryIds = 0;
var queryCallbacks = {};

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

// Call this from the master process. It will start child workers.
//
// options.workerFilename
// Specifies the script to execute for the child processes. Default is
// process.argv[1]
//
// options.args
// Specifies program arguments for the workers. The Default is
// process.argv.slice(2)
//
// options.workers
// The number of workers to start. Defaults to os.cpus().length.
function startMaster() {
  // This can only be called from the master.
  assert(cluster.isMaster);

  if (masterStarted) return;
  masterStarted = true;

  workerFilename = process.argv[1];
  workerArgs = process.argv.slice(2);

  process.on('uncaughtException', function(e) {
    // Quickly try to kill all the workers.
    // TODO: be session leader - will cause auto SIGHUP to the children.
    eachWorker(function(worker) {
      debug('kill worker ' + worker.pid);
      worker.kill();
    });

    console.error('Exception in cluster master process: ' +
        e.message + '\n' + e.stack);
    process.exit(1);
  });
}


function handleWorkerMessage(worker, message) {
  // This can only be called from the master.
  assert(cluster.isMaster);

  debug('recv ' + JSON.stringify(message));

  switch (message.cmd) {
    case 'online':
      debug('Worker ' + worker.pid + ' online');
      worker.online = true;
      break;

    case 'queryServer':
      var key = message.address + ':' +
                message.port + ':' +
                message.addressType;
      var response = { _queryId: message._queryId };

      if (!(key in servers)) {
        // Create a new server.
        debug('create new server ' + key);
        servers[key] = net._createServerHandle(message.address,
                                               message.port,
                                               message.addressType);
      }
      worker.send(response, servers[key]);
      break;

    default:
      // Ignore.
      break;
  }
}


function eachWorker(cb) {
  // This can only be called from the master.
  assert(cluster.isMaster);

  for (var id in workers) {
    if (workers[id]) {
      cb(workers[id]);
    }
  }
}


cluster.fork = function() {
  // This can only be called from the master.
  assert(cluster.isMaster);

  // Lazily start the master process stuff.
  startMaster();

  var id = ++ids;
  var envCopy = {};

  for (var x in process.env) {
    envCopy[x] = process.env[x];
  }

  envCopy['NODE_WORKER_ID'] = id;

  var worker = fork(workerFilename, workerArgs, { env: envCopy });

  workers[id] = worker;

  worker.on('message', function(message) {
    handleWorkerMessage(worker, message);
  });

  worker.on('exit', function() {
    debug('worker id=' + id + ' died');
    delete workers[id];
    cluster.emit('death', worker);
  });

  return worker;
};


// Internal function. Called from src/node.js when worker process starts.
cluster._startWorker = function() {
  assert(cluster.isWorker);
  workerId = parseInt(process.env.NODE_WORKER_ID, 10);

  queryMaster({ cmd: 'online' });

  // Make callbacks from queryMaster()
  process.on('message', function(msg, handle) {
    debug('recv ' + JSON.stringify(msg));
    if (msg._queryId && msg._queryId in queryCallbacks) {
      var cb = queryCallbacks[msg._queryId];
      if (typeof cb == 'function') {
        cb(msg, handle);
      }
      delete queryCallbacks[msg._queryId];
    }
  });
};


function queryMaster(msg, cb) {
  assert(cluster.isWorker);

  debug('send ' + JSON.stringify(msg));

  // Grab some random queryId
  msg._queryId = (++queryIds);
  msg._workerId = workerId;

  // Store callback for later. Callback called in _startWorker.
  if (cb) {
    queryCallbacks[msg._queryId] = cb;
  }

  // Send message to master.
  process.send(msg);
}


// Internal function. Called by lib/net.js when attempting to bind a
// server.
cluster._getServer = function(address, port, addressType, cb) {
  assert(cluster.isWorker);

  queryMaster({
    cmd: 'queryServer',
    address: address,
    port: port,
    addressType: addressType
  }, function(msg, handle) {
    cb(handle);
  });
};