worker: add setEnvironmentData/getEnvironmentData

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 https://github.com/nodejs/node/issues/30992
but does not implement a complete fix.

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

PR-URL: https://github.com/nodejs/node/pull/37486
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>

1 files changed, 49 insertions, 0 deletions

diff --git a/doc/api/worker_threads.md b/doc/api/worker_threads.md
index 7942788df58..c8fc33750ee 100644
--- a/doc/api/worker_threads.md
+++ b/doc/api/worker_threads.md
@@ -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
@@ -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