cluster: support stdio option for workers

This commit allows setupMaster() to configure the stdio channels for worker processes. Refs: nodejs/node-v0.x-archive#5727 Refs: #7811 PR-URL: #7838 Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com>

Author: cjihrig

doc/api/cluster.md

@@ -626,6 +626,9 @@ values are `"rr"` and `"none"`.
  (Default=`process.argv.slice(2)`)
  * `silent` {Boolean} whether or not to send output to parent's stdio.
  (Default=`false`)
+ * `stdio` {Array} Configures the stdio of forked processes. Because the
+ cluster module relies on IPC to function, this configuration must contain an
+ `'ipc'` entry. When this option is provided, it overrides `silent`.
  * `uid` {Number} Sets the user identity of the process. (See setuid(2).)
  * `gid` {Number} Sets the group identity of the process. (See setgid(2).)
 
@@ -642,6 +645,8 @@ This object is not supposed to be changed or set manually, by you.
  (Default=`process.argv.slice(2)`)
  * `silent` {Boolean} whether or not to send output to parent's stdio.
  (Default=`false`)
+ * `stdio` {Array} Configures the stdio of forked processes. When this option
+ is provided, it overrides `silent`.
 
 `setupMaster` is used to change the default 'fork' behavior. Once called,
 the settings will be present in `cluster.settings`.

lib/cluster.js

@@ -321,6 +321,7 @@ function masterInit() {
  env: workerEnv,
  silent: cluster.settings.silent,
  execArgv: execArgv,
+ stdio: cluster.settings.stdio,
  gid: cluster.settings.gid,
  uid: cluster.settings.uid
  });

test/parallel/test-cluster-fork-stdio.js

@@ -0,0 +1,40 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const cluster = require('cluster');
+const net = require('net');
+
+if (cluster.isMaster) {
+ const buf = Buffer.from('foobar');
+
+ cluster.setupMaster({
+ stdio: ['pipe', 'pipe', 'pipe', 'ipc', 'pipe']
+ });
+
+ const worker = cluster.fork();
+ const channel = worker.process.stdio[4];
+ let response = '';
+
+ worker.on('exit', common.mustCall((code, signal) => {
+ assert.strictEqual(code, 0);
+ assert.strictEqual(signal, null);
+ }));
+
+ channel.setEncoding('utf8');
+ channel.on('data', (data) => {
+ response += data;
+
+ if (response === buf.toString()) {
+ worker.disconnect();
+ }
+ });
+ channel.write(buf);
+} else {
+ const pipe = new net.Socket({ fd: 4 });
+
+ pipe.unref();
+ pipe.on('data', (data) => {
+ assert.ok(data instanceof Buffer);
+ pipe.write(data);
+ });
+}