[api] Expose Monitor.fork for using child_process.fork()

lib/forever/monitor.js

@@ -158,17 +158,17 @@ Monitor.prototype.start = function (restart) {
     self.emit(restart ? 'restart' : 'start', self, self.data);
   });
 
-  function reemit() {
-    self.emit.apply(self, arguments);
+  function onMessage(msg) {
+    self.emit('message', msg);
   }
 
   // Re-emit messages from the child process
-  this.child.on('message', reemit);
+  this.child.on('message', onMessage);
 
   child.on('exit', function (code) {
     var spinning = Date.now() - self.ctime < self.minUptime;
     self.warn('Forever detected script exited with code: ' + code);
-    child.removeListener('message', reemit);
+    child.removeListener('message', onMessage);
 
     function letChildDie() {
       self.running = false;
@@ -210,9 +210,6 @@ Monitor.prototype.start = function (restart) {
 // trying to execute a script with an env: e.g. node myfile.js
 //
 Monitor.prototype.trySpawn = function () {
-  var execPath = process.execPath,
-      forked;
-
   if (this.command === 'node' || (this.checkFile && !this.childExists)) {
     try {
       var stats = fs.statSync(this.args[0]);
@@ -226,14 +223,9 @@ Monitor.prototype.trySpawn = function () {
   this.spawnWith.cwd = this.cwd || this.spawnWith.cwd;
   this.spawnWith.env = this._getEnv();
 
-  if (this.command === 'node' || this.fork) {
-    process.execPath = this.command;
-    forked = fork(this.options[0], this.options.slice(1), this.spawnWith);
-    process.execPath = execPath;
-    return forked;
-  }
-
-  return spawn(this.command, this.options, this.spawnWith);
+  return this.fork
+    ? this._forkSpawn()
+    : spawn(this.command, this.options, this.spawnWith);
 };
 
 //
@@ -402,3 +394,47 @@ Monitor.prototype._getEnv = function () {
 
   return merged;
 };
+
+//
+// ### @private function _forkSpawn()
+//
+// This is an unfortunate hack which works around two inconsistencies
+// in the `child_process` APIs in node.js core as of `v0.6.6`. Pull-requests
+// are open to resolve both issues.
+//
+// https://github.com/joyent/node/pull/2455
+// https://github.com/joyent/node/pull/2454
+//
+// Until then, setup `options.customFds` to always return null.
+//
+//
+Monitor.prototype._forkSpawn = function () {
+  var execPath = process.execPath,
+      hackSpawn = {},
+      self = this,
+      forked;
+
+  if (this.spawnWith && typeof this.spawnWith === 'object') {
+    Object.keys(this.spawnWith).forEach(function (key) {
+      hackSpawn[key] = self.spawnWith[key];
+    });
+  }
+
+  delete hackSpawn.customFds;
+  Object.defineProperty(hackSpawn, 'customFds', {
+    get: function () {
+      return null;
+    },
+    set: function () {
+      //
+      // Do nothing, ignore the attempt to overwrite here:
+      // https://github.com/joyent/node/blob/master/lib/child_process.js#L172
+      //
+    } 
+  });
+
+  process.execPath = this.command;
+  forked = fork(this.options[0], this.options.slice(1), hackSpawn);
+  process.execPath = execPath;
+  return forked;
+};

test/fork-test.js

@@ -11,18 +11,19 @@ var assert = require('assert'),
     vows = require('vows'),
     forever = require('../lib/forever');
 
-vows.describe('forever/spin-restart').addBatch({
+vows.describe('forever/fork').addBatch({
   "When using forever": {
     "and spawning a script that uses `process.send()`": {
       topic: function () {
         var script = path.join(__dirname, '..', 'examples', 'process-send.js'),
-            child = new (forever.Monitor)(script, { silent: true, minUptime: 2000, max: 1 });
+            child = new (forever.Monitor)(script, { silent: false, minUptime: 2000, max: 1, fork: true });
 
         child.on('message', this.callback.bind(null, null));
         child.start();
       },
-      "should reemit the message correctly": function (err, child, spinning) {
-        console.dir(arguments);
+      "should reemit the message correctly": function (err, msg) {
+        assert.isObject(msg);
+        assert.deepEqual(msg, { from: 'child' });
       }
     }
   }