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lib,src: update cluster to use Parent #36478

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lib,src: update cluster to use Parent
mhdawson Dec 10, 2020
6631724
squash: use primary instead of parent
mhdawson Dec 17, 2020
4378cdf
Update doc/api/cluster.md
mhdawson Dec 21, 2020
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Update lib/internal/cluster/child.js
mhdawson Dec 21, 2020
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Update test/fixtures/cluster-preload.js
mhdawson Dec 21, 2020
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Update lib/internal/cluster/primary.js
mhdawson Dec 21, 2020
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Update doc/api/cluster.md
mhdawson Dec 21, 2020
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address comments
mhdawson Dec 21, 2020
0210b8f
fixup
mhdawson Dec 21, 2020
89bddae
fixup
mhdawson Dec 21, 2020
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Update doc/api/cluster.md
mhdawson Jan 4, 2021
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Update doc/api/cluster.md
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127 changes: 73 additions & 54 deletions doc/api/cluster.md
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Original file line number Diff line number Diff line change
Expand Up @@ -18,8 +18,8 @@ const cluster = require('cluster');
const http = require('http');
const numCPUs = require('os').cpus().length;

if (cluster.isMaster) {
console.log(`Master ${process.pid} is running`);
if (cluster.isPrimary) {
console.log(`Primary ${process.pid} is running`);

// Fork workers.
for (let i = 0; i < numCPUs; i++) {
Expand All @@ -45,7 +45,7 @@ Running Node.js will now share port 8000 between the workers:

```console
$ node server.js
Master 3596 is running
Primary 3596 is running
Worker 4324 started
Worker 4520 started
Worker 6056 started
Expand All @@ -66,12 +66,12 @@ The cluster module supports two methods of distributing incoming
connections.

The first one (and the default one on all platforms except Windows),
is the round-robin approach, where the master process listens on a
is the round-robin approach, where the primary process listens on a
port, accepts new connections and distributes them across the workers
in a round-robin fashion, with some built-in smarts to avoid
overloading a worker process.

The second approach is where the master process creates the listen
The second approach is where the primary process creates the listen
socket and sends it to interested workers. The workers then accept
incoming connections directly.

Expand All @@ -81,16 +81,16 @@ to operating system scheduler vagaries. Loads have been observed
where over 70% of all connections ended up in just two processes,
out of a total of eight.

Because `server.listen()` hands off most of the work to the master
Because `server.listen()` hands off most of the work to the primary
process, there are three cases where the behavior between a normal
Node.js process and a cluster worker differs:

1. `server.listen({fd: 7})` Because the message is passed to the master,
1. `server.listen({fd: 7})` Because the message is passed to the primary,
file descriptor 7 **in the parent** will be listened on, and the
handle passed to the worker, rather than listening to the worker's
idea of what the number 7 file descriptor references.
2. `server.listen(handle)` Listening on handles explicitly will cause
the worker to use the supplied handle, rather than talk to the master
the worker to use the supplied handle, rather than talk to the primary
process.
3. `server.listen(0)` Normally, this will cause servers to listen on a
random port. However, in a cluster, each worker will receive the
Expand Down Expand Up @@ -121,7 +121,7 @@ added: v0.7.0
* Extends: {EventEmitter}

A `Worker` object contains all public information and method about a worker.
In the master it can be obtained using `cluster.workers`. In a worker
In the primary it can be obtained using `cluster.workers`. In a worker
it can be obtained using `cluster.worker`.

### Event: `'disconnect'`
Expand Down Expand Up @@ -201,14 +201,14 @@ Within a worker, `process.on('message')` may also be used.

See [`process` event: `'message'`][].

Here is an example using the message system. It keeps a count in the master
Here is an example using the message system. It keeps a count in the primary
process of the number of HTTP requests received by the workers:

```js
const cluster = require('cluster');
const http = require('http');

if (cluster.isMaster) {
if (cluster.isPrimary) {

// Keep track of http requests
let numReqs = 0;
Expand Down Expand Up @@ -240,7 +240,7 @@ if (cluster.isMaster) {
res.writeHead(200);
res.end('hello world\n');

// Notify master about the request
// Notify primary about the request
process.send({ cmd: 'notifyRequest' });
}).listen(8000);
}
Expand Down Expand Up @@ -275,7 +275,7 @@ changes:
In a worker, this function will close all servers, wait for the `'close'` event
on those servers, and then disconnect the IPC channel.

In the master, an internal message is sent to the worker causing it to call
In the primary, an internal message is sent to the worker causing it to call
`.disconnect()` on itself.

Causes `.exitedAfterDisconnect` to be set.
Expand All @@ -299,7 +299,7 @@ close them. It also may be useful to implement a timeout, killing a worker if
the `'disconnect'` event has not been emitted after some time.

```js
if (cluster.isMaster) {
if (cluster.isPrimary) {
const worker = cluster.fork();
let timeout;

Expand Down Expand Up @@ -343,7 +343,7 @@ This property is `true` if the worker exited due to `.kill()` or
worker has not exited, it is `undefined`.

The boolean [`worker.exitedAfterDisconnect`][] allows distinguishing between
voluntary and accidental exit, the master may choose not to respawn a worker
voluntary and accidental exit, the primary may choose not to respawn a worker
based on this value.

```js
Expand Down Expand Up @@ -375,8 +375,8 @@ While a worker is alive, this is the key that indexes it in
added: v0.11.14
-->

This function returns `true` if the worker is connected to its master via its
IPC channel, `false` otherwise. A worker is connected to its master after it
This function returns `true` if the worker is connected to its primary via its
IPC channel, `false` otherwise. A worker is connected to its primary after it
has been created. It is disconnected after the `'disconnect'` event is emitted.

### `worker.isDead()`
Expand All @@ -392,8 +392,8 @@ const cluster = require('cluster');
const http = require('http');
const numCPUs = require('os').cpus().length;

if (cluster.isMaster) {
console.log(`Master ${process.pid} is running`);
if (cluster.isPrimary) {
console.log(`Primary ${process.pid} is running`);

// Fork workers.
for (let i = 0; i < numCPUs; i++) {
Expand Down Expand Up @@ -425,9 +425,10 @@ added: v0.9.12
* `signal` {string} Name of the kill signal to send to the worker
process. **Default**: `'SIGTERM'`

This function will kill the worker. In the master, it does this by disconnecting
the `worker.process`, and once disconnected, killing with `signal`. In the
worker, it does it by disconnecting the channel, and then exiting with code `0`.
This function will kill the worker. In the primary, it does this
by disconnecting the `worker.process`, and once disconnected, killing
with `signal`. In the worker, it does it by disconnecting the channel,
and then exiting with code `0`.

Because `kill()` attempts to gracefully disconnect the worker process, it is
susceptible to waiting indefinitely for the disconnect to complete. For example,
Expand Down Expand Up @@ -478,18 +479,18 @@ changes:
* `callback` {Function}
* Returns: {boolean}

Send a message to a worker or master, optionally with a handle.
Send a message to a worker or primary, optionally with a handle.

In the master this sends a message to a specific worker. It is identical to
In the primary this sends a message to a specific worker. It is identical to
[`ChildProcess.send()`][].

In a worker this sends a message to the master. It is identical to
In a worker this sends a message to the primary. It is identical to
`process.send()`.

This example will echo back all messages from the master:
This example will echo back all messages from the primary:

```js
if (cluster.isMaster) {
if (cluster.isPrimary) {
const worker = cluster.fork();
worker.send('hi there');

Expand Down Expand Up @@ -583,7 +584,7 @@ added: v0.7.0

After calling `listen()` from a worker, when the `'listening'` event is emitted
on the server a `'listening'` event will also be emitted on `cluster` in the
master.
primary.

The event handler is executed with two arguments, the `worker` contains the
worker object and the `address` object contains the following connection
Expand Down Expand Up @@ -617,7 +618,7 @@ changes:
* `message` {Object}
* `handle` {undefined|Object}

Emitted when the cluster master receives a message from any worker.
Emitted when the cluster primary receives a message from any worker.

See [`child_process` event: `'message'`][].

Expand All @@ -629,9 +630,9 @@ added: v0.7.0
* `worker` {cluster.Worker}

After forking a new worker, the worker should respond with an online message.
When the master receives an online message it will emit this event.
When the primary receives an online message it will emit this event.
The difference between `'fork'` and `'online'` is that fork is emitted when the
master forks a worker, and `'online'` is emitted when the worker is running.
primary forks a worker, and `'online'` is emitted when the worker is running.

```js
cluster.on('online', (worker) => {
Expand All @@ -646,11 +647,11 @@ added: v0.7.1

* `settings` {Object}

Emitted every time [`.setupMaster()`][] is called.
Emitted every time [`.setupPrimary()`][] is called.

The `settings` object is the `cluster.settings` object at the time
[`.setupMaster()`][] was called and is advisory only, since multiple calls to
[`.setupMaster()`][] can be made in a single tick.
[`.setupPrimary()`][] was called and is advisory only, since multiple calls to
[`.setupPrimary()`][] can be made in a single tick.

If accuracy is important, use `cluster.settings`.

Expand All @@ -665,12 +666,12 @@ added: v0.7.7
Calls `.disconnect()` on each worker in `cluster.workers`.

When they are disconnected all internal handles will be closed, allowing the
master process to die gracefully if no other event is waiting.
primary process to die gracefully if no other event is waiting.

The method takes an optional callback argument which will be called when
finished.

This can only be called from the master process.
This can only be called from the primary process.

## `cluster.fork([env])`
<!-- YAML
Expand All @@ -682,18 +683,27 @@ added: v0.6.0

Spawn a new worker process.

This can only be called from the master process.
This can only be called from the primary process.

## `cluster.isMaster`
<!-- YAML
added: v0.8.1
targos marked this conversation as resolved.
Show resolved Hide resolved
deprecated: REPLACEME
-->

Deprecated alias for [`cluster.isPrimary`][].
details.

## `cluster.isPrimary`
<!-- YAML
added: REPLACEME
-->

* {boolean}

True if the process is a master. This is determined
True if the process is a primary. This is determined
by the `process.env.NODE_UNIQUE_ID`. If `process.env.NODE_UNIQUE_ID` is
undefined, then `isMaster` is `true`.
undefined, then `isPrimary` is `true`.

## `cluster.isWorker`
<!-- YAML
Expand All @@ -702,7 +712,7 @@ added: v0.6.0

* {boolean}

True if the process is not a master (it is the negation of `cluster.isMaster`).
True if the process is not a primary (it is the negation of `cluster.isPrimary`).

## `cluster.schedulingPolicy`
<!-- YAML
Expand All @@ -712,7 +722,7 @@ added: v0.11.2
The scheduling policy, either `cluster.SCHED_RR` for round-robin or
`cluster.SCHED_NONE` to leave it to the operating system. This is a
global setting and effectively frozen once either the first worker is spawned,
or [`.setupMaster()`][] is called, whichever comes first.
or [`.setupPrimary()`][] is called, whichever comes first.

`SCHED_RR` is the default on all operating systems except Windows.
Windows will change to `SCHED_RR` once libuv is able to effectively
Expand Down Expand Up @@ -767,54 +777,62 @@ changes:
* `inspectPort` {number|Function} Sets inspector port of worker.
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`.
primary'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
After calling [`.setupPrimary()`][] (or [`.fork()`][]) this settings object will
contain the settings, including the default values.

This object is not intended to be changed or set manually.

## `cluster.setupMaster([settings])`
<!-- YAML
added: v0.7.1
deprecated: REPLACEME
changes:
- version: v6.4.0
pr-url: https://github.com/nodejs/node/pull/7838
description: The `stdio` option is supported now.
targos marked this conversation as resolved.
Show resolved Hide resolved
-->

Deprecated alias for [`.setupPrimary()`][].

## `cluster.setupPrimary([settings])`
<!-- YAML
added: REPLACEME
-->

* `settings` {Object} See [`cluster.settings`][].

`setupMaster` is used to change the default 'fork' behavior. Once called,
`setupPrimary` is used to change the default 'fork' behavior. Once called,
the settings will be present in `cluster.settings`.

Any settings changes only affect future calls to [`.fork()`][] and have no
effect on workers that are already running.

The only attribute of a worker that cannot be set via `.setupMaster()` is
The only attribute of a worker that cannot be set via `.setupPrimary()` is
the `env` passed to [`.fork()`][].

The defaults above apply to the first call only; the defaults for later
calls are the current values at the time of `cluster.setupMaster()` is called.
calls are the current values at the time of `cluster.setupPrimary()` is called.

```js
const cluster = require('cluster');
cluster.setupMaster({
cluster.setupPrimary({
exec: 'worker.js',
args: ['--use', 'https'],
silent: true
});
cluster.fork(); // https worker
cluster.setupMaster({
cluster.setupPrimary({
exec: 'worker.js',
args: ['--use', 'http']
});
cluster.fork(); // http worker
```

This can only be called from the master process.
This can only be called from the primary process.

## `cluster.worker`
<!-- YAML
Expand All @@ -823,13 +841,13 @@ added: v0.7.0

* {Object}

A reference to the current worker object. Not available in the master process.
A reference to the current worker object. Not available in the primary process.

```js
const cluster = require('cluster');

if (cluster.isMaster) {
console.log('I am master');
if (cluster.isPrimary) {
console.log('I am primary');
cluster.fork();
cluster.fork();
} else if (cluster.isWorker) {
Expand All @@ -845,7 +863,7 @@ added: v0.7.0
* {Object}

A hash that stores the active worker objects, keyed by `id` field. Makes it
easy to loop through all the workers. It is only available in the master
easy to loop through all the workers. It is only available in the primary
process.

A worker is removed from `cluster.workers` after the worker has disconnected
Expand Down Expand Up @@ -876,13 +894,14 @@ socket.on('data', (id) => {
[Advanced serialization for `child_process`]: child_process.md#child_process_advanced_serialization
[Child Process module]: child_process.md#child_process_child_process_fork_modulepath_args_options
[`.fork()`]: #cluster_cluster_fork_env
[`.setupMaster()`]: #cluster_cluster_setupmaster_settings
[`.setupPrimary()`]: #cluster_cluster_setupprimary_settings
[`ChildProcess.send()`]: child_process.md#child_process_subprocess_send_message_sendhandle_options_callback
[`child_process.fork()`]: child_process.md#child_process_child_process_fork_modulepath_args_options
[`child_process` event: `'exit'`]: child_process.md#child_process_event_exit
[`child_process` event: `'message'`]: child_process.md#child_process_event_message
[`cluster.settings`]: #cluster_cluster_settings
[`disconnect()`]: child_process.md#child_process_subprocess_disconnect
[`cluster.isPrimary`]: #cluster_cluster_isprimary
[`kill()`]: process.md#process_process_kill_pid_signal
[`process` event: `'message'`]: process.md#process_event_message
[`server.close()`]: net.md#net_event_close
Expand Down
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