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cluster: support windowsHide option for workers #17412

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2 changes: 2 additions & 0 deletions doc/api/cluster.md
Original file line number Diff line number Diff line change
Expand Up @@ -722,6 +722,8 @@ changes:
This can be a number, or a function that takes no arguments and returns a
number. By default each worker gets its own port, incremented from the
master's `process.debugPort`.
* `windowsHide` {boolean} Hide the forked processes console window that would
normally be created on Windows systems. **Default:** `false`

After calling `.setupMaster()` (or `.fork()`) this settings object will contain
the settings, including the default values.
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1 change: 1 addition & 0 deletions lib/internal/cluster/master.js
Original file line number Diff line number Diff line change
Expand Up @@ -127,6 +127,7 @@ function createWorkerProcess(id, env) {
return fork(cluster.settings.exec, cluster.settings.args, {
env: workerEnv,
silent: cluster.settings.silent,
windowsHide: cluster.settings.windowsHide,
execArgv: execArgv,
stdio: cluster.settings.stdio,
gid: cluster.settings.gid,
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77 changes: 77 additions & 0 deletions test/parallel/test-cluster-fork-windowsHide.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,77 @@
'use strict';
const common = require('../common');
const assert = require('assert');
const child_process = require('child_process');

let patchedFork = child_process.fork;
child_process.fork = (...args) => patchedFork.apply(this, args);
const cluster = require('cluster');
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You can get rid of the monkey-patch now because ultimately it doesn't how matter how the option is passed down, as long as the observable effect is the same.

Presumably the child_process.spawn() call can go too? I admit I don't quite understand why you run the tests in a child process.

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@toddwong toddwong Dec 3, 2017

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I keep the monkey-patch just in case some one run the tests on other platforms or in a windows service session. Not sure if this is necessary or practically useful.

It seems Windows only allocate a new console window for an attaching process spawned by a detached process.

If process D is spawned by process C with detached: true , and process W is spawned by process D with detached: false, W will get a new black console window popped up.

if D is spawned by C with detached: false or W is spawned by D with detached: true, no console window will pop up for W.

C = Command, D = Daemon, W = worker, practically.

That's why the test need to be run in a (detached) child process.

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@bnoordhuis Is this OK?

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I keep the monkey-patch just in case some one run the tests on other platforms or in a windows service session. Not sure if this is necessary or practically useful.

Neither, I'd say. :-)

Can you add a comment to the test that explains why it spawns a child process first? I get it now from your explanation but it's not obvious from just looking at the code.

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Sure, i'll add the comment, and remove the monkey-patch thing.


if (!process.argv[2]) {
const master = child_process.spawn(
process.argv[0],
[process.argv[1], '--cluster'],
{ detached: true, stdio: ['ignore', 'ignore', 'ignore', 'ipc'] });

const messageHandlers = {
windowsHide: common.mustCall((msg) => {
assert.strictEqual(msg.value, true);
}),
workerOnline: common.mustCall((msg) => {
}),
mainWindowHandle: common.mustCall((msg) => {
assert.ok(/0\s*/.test(msg.value));
}),
workerExit: common.mustCall((msg) => {
assert.strictEqual(msg.code, 0);
assert.strictEqual(msg.signal, null);
})
};

master.on('message', (msg) => {
const handler = messageHandlers[msg.type];
assert.ok(handler);
handler(msg);
});

master.on('exit', common.mustCall((code, signal) => {
assert.strictEqual(code, 0);
assert.strictEqual(signal, null);
}));

} else if (cluster.isMaster) {
const originalFork = patchedFork;
patchedFork = common.mustCall((...args) => {
process.send({ type: 'windowsHide', value: args[2].windowsHide });
return originalFork.apply(this, args);
});

cluster.setupMaster({
silient: true,
windowsHide: true
});

const worker = cluster.fork();
worker.on('exit', (code, signal) => {
process.send({ type: 'workerExit', code: code, signal: signal });
});

worker.on('online', (msg) => {
process.send({ type: 'workerOnline' });

let output = '0';
if (process.platform === 'win32')
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Braces please for multi-line bodies.

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Fixed!

output = child_process.execSync(
'powershell -NoProfile -c ' +
`"(Get-Process -Id ${worker.process.pid}).MainWindowHandle"`,
{ windowsHide: true, encoding: 'utf8' });

process.send({ type: 'mainWindowHandle', value: output });
worker.send('shutdown');
});

} else {
cluster.worker.on('message', (msg) => {
cluster.worker.disconnect();
});
}