cluster: report EADDRINUSE when a worker listens twice on the same port

Author: islandryu

lib/internal/cluster/primary.js

@@ -16,6 +16,7 @@ const {
 } = require('internal/errors');
 
 const assert = require('internal/assert');
+const { UV_EADDRINUSE } = internalBinding('uv');
 const { fork } = require('child_process');
 const path = require('path');
 const EventEmitter = require('events');
@@ -274,7 +275,16 @@ function queryServer(worker, message) {
               `${message.fd}` + (message.port === 0 ? `:${message.index}` : '');
   const cachedHandle = handles.get(key);
   let handle;
-  if (cachedHandle && !cachedHandle.has(worker)) {
+  if (cachedHandle) {
+    if (cachedHandle.has(worker)) {
+      send(worker, {
+        errno: UV_EADDRINUSE,
+        key,
+        ack: message.seq,
+        data: cachedHandle.data,
+      });
+      return;
+    }
     handle = cachedHandle;
   }
 

test/sequential/test-cluster-listen-twice-same-port.js

@@ -0,0 +1,29 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const cluster = require('cluster');
+const net = require('net');
+
+if (cluster.isPrimary) {
+  cluster.fork().on('exit', common.mustCall((code) => {
+    assert.strictEqual(code, 0);
+  }));
+  return;
+}
+
+function listen() {
+  return new Promise((resolve, reject) => {
+    const server = net.createServer();
+    server.once('error', reject);
+    server.once('listening', () => resolve(server));
+    server.listen({ host: '127.0.0.1', port: common.PORT });
+  });
+}
+
+(async () => {
+  const server1 = await listen();
+  await assert.rejects(listen(), { code: 'EADDRINUSE' });
+  await new Promise((resolve) => server1.close(resolve));
+  cluster.worker.disconnect();
+})().then(common.mustCall());