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worker: add setEnvironmentData/getEnvironmentData
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These APIs allow arbitrary, cloneable JavaScript values to be set and
passed to all new Worker instances spawned from the current context.
It is similar to `workerData` except that environment data is set
independently of the `new Worker()` constructor, and the the value is
passed automatically to all new Workers.

This is a *partial* fix of #30992
but does not implement a complete fix.

Signed-off-by: James M Snell <jasnell@gmail.com>

PR-URL: #37486
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
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jasnell authored and danielleadams committed Mar 16, 2021
1 parent 5d79373 commit 0d135e8
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49 changes: 49 additions & 0 deletions doc/api/worker_threads.md
Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,38 @@ Worker threads inherit non-process-specific options by default. Refer to
[`Worker constructor options`][] to know how to customize worker thread options,
specifically `argv` and `execArgv` options.

## `worker.getEnvironmentData(key)`
<!-- YAML
added: REPLACEME
-->

> Stability: 1 - Experimental
* `key` {any} Any arbitrary, cloneable JavaScript value that can be used as a
{Map} key.
* Returns: {any}

Within a worker thread, `worker.getEnvironmentData()` returns a clone
of data passed to the spawning thread's `worker.setEnvironmentData()`.
Every new `Worker` receives its own copy of the environment data
automatically.

```js
const {
Worker,
isMainThread,
setEnvironmentData,
getEnvironmentData,
} = require('worker_threads');

if (isMainThread) {
setEnvironmentData('Hello', 'World!');
const worker = new Worker(__filename);
} else {
console.log(getEnvironmentData('Hello')); // Prints 'World!'.
}
```

## `worker.isMainThread`
<!-- YAML
added: v10.5.0
Expand Down Expand Up @@ -246,6 +278,23 @@ new Worker('process.env.SET_IN_WORKER = "foo"', { eval: true, env: SHARE_ENV })
});
```

## `worker.setEnvironmentData(key[, value])`
<!--YAML
added: REPLACEME
-->

> Stability: 1 - Experimental
* `key` {any} Any arbitrary, cloneable JavaScript value that can be used as a
{Map} key.
* `value` {any} Any arbitrary, cloneable JavaScript value that will be cloned
and passed automatically to all new `Worker` instances. If `value` is passed
as `undefined`, any previously set value for the `key` will be deleted.

The `worker.setEnvironmentData()` API sets the content of
`worker.getEnvironmentData()` in the current thread and all new `Worker`
instances spawned from the current context.

## `worker.threadId`
<!-- YAML
added: v10.5.0
Expand Down
3 changes: 3 additions & 0 deletions lib/internal/main/worker_thread.js
Original file line number Diff line number Diff line change
Expand Up @@ -105,6 +105,7 @@ port.on('message', (message) => {
filename,
doEval,
workerData,
environmentData,
publicPort,
manifestSrc,
manifestURL,
Expand All @@ -127,6 +128,8 @@ port.on('message', (message) => {
publicWorker.parentPort = publicPort;
publicWorker.workerData = workerData;

require('internal/worker').assignEnvironmentData(environmentData);

// The counter is only passed to the workers created by the main thread, not
// to workers created by other workers.
let cachedCwd = '';
Expand Down
25 changes: 25 additions & 0 deletions lib/internal/worker.js
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ const {
ReflectApply,
RegExpPrototypeTest,
SafeArrayIterator,
SafeMap,
String,
Symbol,
SymbolFor,
Expand Down Expand Up @@ -90,6 +91,8 @@ let debug = require('internal/util/debuglog').debuglog('worker', (fn) => {

let cwdCounter;

const environmentData = new SafeMap();

if (isMainThread) {
cwdCounter = new Uint32Array(new SharedArrayBuffer(4));
const originalChdir = process.chdir;
Expand All @@ -99,6 +102,24 @@ if (isMainThread) {
};
}

function setEnvironmentData(key, value) {
if (value === undefined)
environmentData.delete(key);
else
environmentData.set(key, value);
}

function getEnvironmentData(key) {
return environmentData.get(key);
}

function assignEnvironmentData(data) {
if (data === undefined) return;
data.forEach((value, key) => {
environmentData.set(key, value);
});
}

class Worker extends EventEmitter {
constructor(filename, options = {}) {
super();
Expand Down Expand Up @@ -228,6 +249,7 @@ class Worker extends EventEmitter {
doEval,
cwdCounter: cwdCounter || workerIo.sharedCwdCounter,
workerData: options.workerData,
environmentData,
publicPort: port2,
manifestURL: getOptionValue('--experimental-policy') ?
require('internal/process/policy').url :
Expand Down Expand Up @@ -493,6 +515,9 @@ module.exports = {
SHARE_ENV,
resourceLimits:
!isMainThread ? makeResourceLimits(resourceLimitsRaw) : {},
setEnvironmentData,
getEnvironmentData,
assignEnvironmentData,
threadId,
Worker,
};
4 changes: 4 additions & 0 deletions lib/worker_threads.js
Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,8 @@ const {
isMainThread,
SHARE_ENV,
resourceLimits,
setEnvironmentData,
getEnvironmentData,
threadId,
Worker
} = require('internal/worker');
Expand Down Expand Up @@ -34,4 +36,6 @@ module.exports = {
parentPort: null,
workerData: null,
BroadcastChannel,
setEnvironmentData,
getEnvironmentData,
};
33 changes: 33 additions & 0 deletions test/parallel/test-worker-environmentdata.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,33 @@
'use strict';

require('../common');
const {
Worker,
getEnvironmentData,
setEnvironmentData,
threadId,
} = require('worker_threads');

const {
deepStrictEqual,
strictEqual,
} = require('assert');

if (!process.env.HAS_STARTED_WORKER) {
process.env.HAS_STARTED_WORKER = 1;
setEnvironmentData('foo', 'bar');
setEnvironmentData('hello', { value: 'world' });
setEnvironmentData(1, 2);
strictEqual(getEnvironmentData(1), 2);
setEnvironmentData(1); // Delete it, key won't show up in the worker.
new Worker(__filename);
setEnvironmentData('hello'); // Delete it. Has no impact on the worker.
} else {
strictEqual(getEnvironmentData('foo'), 'bar');
deepStrictEqual(getEnvironmentData('hello'), { value: 'world' });
strictEqual(getEnvironmentData(1), undefined);

// Recurse to make sure the environment data is inherited
if (threadId <= 2)
new Worker(__filename);
}

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