lib: add diagnostics channel for process and worker

PR-URL: https://github.com/nodejs/node/pull/44045
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/diagnostics_channel.md

@@ -434,6 +434,8 @@ Emitted when server receives a request.
 
 Emitted when server sends a response.
 
+#### NET
+
 `net.client.socket`
 
 * `socket` {net.Socket}
@@ -446,13 +448,40 @@ Emitted when a new TCP or pipe client socket is created.
 
 Emitted when a new TCP or pipe connection is received.
 
+#### UDP
+
 `udp.socket`
 
 * `socket` {dgram.Socket}
 
 Emitted when a new UDP socket is created.
 
+#### Process
+
+<!-- YAML
+added: REPLACEME
+-->
+
+`child_process`
+
+* `process` {ChildProcess}
+
+Emitted when a new process is created.
+
+#### Worker Thread
+
+<!-- YAML
+added: REPLACEME
+-->
+
+`worker_threads`
+
+* `worker` [`Worker`][]
+
+Emitted when a new thread is created.
+
 [`'uncaughtException'`]: process.md#event-uncaughtexception
+[`Worker`]: worker_threads.md#class-worker
 [`channel.subscribe(onMessage)`]: #channelsubscribeonmessage
 [`diagnostics_channel.channel(name)`]: #diagnostics_channelchannelname
 [`diagnostics_channel.subscribe(name, onMessage)`]: #diagnostics_channelsubscribename-onmessage

lib/internal/child_process.js

@@ -59,6 +59,8 @@ const { convertToValidSignal, deprecate } = require('internal/util');
 const { isArrayBufferView } = require('internal/util/types');
 const spawn_sync = internalBinding('spawn_sync');
 const { kStateSymbol } = require('internal/dgram');
+const dc = require('diagnostics_channel');
+const childProcessChannel = dc.channel('child_process');
 
 const {
   UV_EACCES,
@@ -301,6 +303,11 @@ function ChildProcess() {
 
     maybeClose(this);
   };
+  if (childProcessChannel.hasSubscribers) {
+    childProcessChannel.publish({
+      process: this,
+    });
+  }
 }
 ObjectSetPrototypeOf(ChildProcess.prototype, EventEmitter.prototype);
 ObjectSetPrototypeOf(ChildProcess, EventEmitter);

lib/internal/worker.js

@@ -89,6 +89,9 @@ let debug = require('internal/util/debuglog').debuglog('worker', (fn) => {
   debug = fn;
 });
 
+const dc = require('diagnostics_channel');
+const workerThreadsChannel = dc.channel('worker_threads');
+
 let cwdCounter;
 
 const environmentData = new SafeMap();
@@ -262,6 +265,11 @@ class Worker extends EventEmitter {
     this[kHandle].startThread();
 
     process.nextTick(() => process.emit('worker', this));
+    if (workerThreadsChannel.hasSubscribers) {
+      workerThreadsChannel.publish({
+        worker: this,
+      });
+    }
   }
 
   [kOnExit](code, customErr, customErrReason) {

test/parallel/test-diagnostics-channel-process.js

@@ -0,0 +1,21 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const cluster = require('cluster');
+const { ChildProcess } = require('child_process');
+const dc = require('diagnostics_channel');
+
+if (cluster.isPrimary) {
+  dc.subscribe('child_process', common.mustCall(({ process }) => {
+    assert.strictEqual(process instanceof ChildProcess, true);
+  }));
+  const worker = cluster.fork();
+  worker.on('online', common.mustCall(() => {
+    worker.send('disconnect');
+  }));
+} else {
+  process.on('message', common.mustCall((msg) => {
+    assert.strictEqual(msg, 'disconnect');
+    process.disconnect();
+  }));
+}

test/parallel/test-diagnostics-channel-worker-threads.js

@@ -0,0 +1,11 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const { Worker } = require('worker_threads');
+const dc = require('diagnostics_channel');
+
+dc.subscribe('worker_threads', common.mustCall(({ worker }) => {
+  assert.strictEqual(worker instanceof Worker, true);
+}));
+
+new Worker('const a = 1;', { eval: true });