cluster: propagate bind errors

This commit fixes a bug where the cluster module fails to propagate
EADDRINUSE errors.

When a worker starts a (net, http) server, it requests the listen socket
from its master who then creates and binds the socket.

Now, OS X and Windows don't always signal EADDRINUSE from bind() but
instead defer the error until a later syscall. libuv mimics this
behaviour to provide consistent behaviour across platforms but that
means the worker could end up with a socket that is not actually bound
to the requested addresss.

That's why the worker now checks if the socket is bound, raising
EADDRINUSE if that's not the case.

Fixes #2721.

3 files changed, 133 insertions, 6 deletions

diff --git a/lib/net.js b/lib/net.js
index c8d7f60913..38985214d6 100644
--- a/lib/net.js
+++ b/lib/net.js
@@ -928,14 +928,26 @@ Server.prototype._listen2 = function(address, port, addressType, backlog, fd) {
 function listen(self, address, port, addressType, backlog, fd) {
   if (!cluster) cluster = require('cluster');
 
-  if (cluster.isWorker) {
-    cluster._getServer(self, address, port, addressType, fd, function(handle) {
-      self._handle = handle;
-      self._listen2(address, port, addressType, backlog, fd);
-    });
-  } else {
+  if (cluster.isMaster) {
     self._listen2(address, port, addressType, backlog, fd);
+    return;
   }
+
+  cluster._getServer(self, address, port, addressType, fd, function(handle) {
+    // Some operating systems (notably OS X and Solaris) don't report EADDRINUSE
+    // errors right away. libuv mimics that behavior for the sake of platform
+    // consistency but that means we have have a socket on our hands that is
+    // not actually bound. That's why we check if the actual port matches what
+    // we requested and if not, raise an error. The exception is when port == 0
+    // because that means "any random port".
+    if (port && handle.getsockname && port != handle.getsockname().port) {
+      self.emit('error', errnoException('EADDRINUSE', 'bind'));
+      return;
+    }
+
+    self._handle = handle;
+    self._listen2(address, port, addressType, backlog, fd);
+  });
 }
 
 
diff --git a/test/simple/test-cluster-bind-twice.js b/test/simple/test-cluster-bind-twice-v1.js
index 068842fa53..068842fa53 100644
--- a/test/simple/test-cluster-bind-twice.js
+++ b/test/simple/test-cluster-bind-twice-v1.js
diff --git a/test/simple/test-cluster-bind-twice-v2.js b/test/simple/test-cluster-bind-twice-v2.js
new file mode 100644
index 0000000000..87a932b5bc
--- /dev/null
+++ b/test/simple/test-cluster-bind-twice-v2.js
@@ -0,0 +1,115 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+// This test starts two clustered HTTP servers on the same port. It expects the
+// first cluster to succeed and the second cluster to fail with EADDRINUSE.
+//
+// The test may seem complex but most of it is plumbing that routes messages
+// from the child processes back to the supervisor. As a tree it looks something
+// like this:
+//
+//          <supervisor>
+//         /            \
+//    <master 1>     <master 2>
+//       /                \
+//  <worker 1>         <worker 2>
+//
+// The first worker starts a server on a fixed port and fires a ready message
+// that is routed to the second worker. When it tries to bind, it expects to
+// see an EADDRINUSE error.
+//
+// See https://github.com/joyent/node/issues/2721 for more details.
+
+var common = require('../common');
+var assert = require('assert');
+var cluster = require('cluster');
+var fork = require('child_process').fork;
+var http = require('http');
+
+var id = process.argv[2];
+
+if (!id) {
+  var a = fork(__filename, ['one']);
+  var b = fork(__filename, ['two']);
+
+  a.on('message', function(m) {
+    if (typeof m === 'object') return;
+    assert.equal(m, 'READY');
+    b.send('START');
+  });
+
+  var ok = false;
+
+  b.on('message', function(m) {
+    if (typeof m === 'object') return; // ignore system messages
+    assert.equal(m, 'EADDRINUSE');
+    a.kill();
+    b.kill();
+    ok = true;
+  });
+
+  process.on('exit', function() {
+    a.kill();
+    b.kill();
+    assert(ok);
+  });
+}
+else if (id === 'one') {
+  if (cluster.isMaster) return startWorker();
+
+  http.createServer(assert.fail).listen(common.PORT, function() {
+    process.send('READY');
+  });
+}
+else if (id === 'two') {
+  if (cluster.isMaster) return startWorker();
+
+  var ok = false;
+  process.on('SIGTERM', process.exit);
+  process.on('exit', function() {
+    assert(ok);
+  });
+
+  process.on('message', function(m) {
+    if (typeof m === 'object') return; // ignore system messages
+    assert.equal(m, 'START');
+    var server = http.createServer(assert.fail);
+    server.listen(common.PORT, assert.fail);
+    server.on('error', function(e) {
+      assert.equal(e.code, 'EADDRINUSE');
+      process.send(e.code);
+      ok = true;
+    });
+  });
+}
+else {
+  assert(0); // bad command line argument
+}
+
+function startWorker() {
+  var worker = cluster.fork();
+  worker.on('message', process.send.bind(process));
+  process.on('message', worker.send.bind(worker));
+  process.on('SIGTERM', function() {
+    worker.destroy();
+    process.exit();
+  });
+}