worker: prevent event loop starvation through MessagePorts

src/node_messaging.cc

@@ -609,11 +609,20 @@ void MessagePort::OnMessage() {
   HandleScope handle_scope(env()->isolate());
   Local<Context> context = object(env()->isolate())->CreationContext();
 
+  int count = 0;
+
   // data_ can only ever be modified by the owner thread, so no need to lock.
   // However, the message port may be transferred while it is processing
   // messages, so we need to check that this handle still owns its `data_` field
   // on every iteration.
   while (data_) {
+    if (count++ == 100) {
+      // Prevent event loop starvation by allowing a maximum of 100 messages
+      // to be processed without interruption.
+      TriggerAsync();
+      return;
+    }
+
     HandleScope handle_scope(env()->isolate());
     Context::Scope context_scope(context);
 

test/parallel/test-worker-message-port-infinite-message-loop.js

@@ -0,0 +1,27 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+
+const { MessageChannel } = require('worker_threads');
+
+// Make sure that an infinite asynchronous .on('message')/postMessage loop
+// does not lead to a stack overflow and does not starve the event loop.
+// We schedule timeouts both from before the the .on('message') handler and
+// inside of it, which both should run.
+
+const { port1, port2 } = new MessageChannel();
+let count = 0;
+port1.on('message', () => {
+  if (count === 0) {
+    setTimeout(common.mustCall(() => {
+      port1.close();
+    }), 0);
+  }
+
+  port2.postMessage(0);
+  assert(count++ < 10000, `hit ${count} loop iterations`);
+});
+
+port2.postMessage(0);
+
+setTimeout(common.mustCall(), 0);