cluster: wait for all servers closing before disconnect

Fix for iojs/io,js#1305
Before this, cluster bahaves not the way it is docummented
Then disconnect is triggered, worker must wait for every server is closed
before doing disconnect actually.

See test case and discussion in the above mentioned issue

lib/cluster.js

@@ -625,12 +625,26 @@ function workerInit() {
 
   Worker.prototype.disconnect = function() {
     this.suicide = true;
+    var waitingHandles = 0;
+
+    function checkRemainingHandles() {
+      waitingHandles--;
+      if (waitingHandles === 0) {
+        process.disconnect();
+      }
+    }
+
     for (var key in handles) {
       var handle = handles[key];
       delete handles[key];
-      handle.close();
+      waitingHandles++;
+      handle.owner.close(checkRemainingHandles);
     }
-    process.disconnect();
+
+    if (waitingHandles === 0) {
+      process.disconnect();
+    }
+
   };
 
   Worker.prototype.destroy = function() {

test/parallel/test-cluster-worker-wait-server-close.js

@@ -0,0 +1,63 @@
+var common = require('../common');
+var assert = require('assert');
+var cluster = require('cluster');
+var net = require('net');
+
+if (cluster.isWorker) {
+  net.createServer(function(socket) {
+    // Wait for any data, then close connection
+    socket.on('data', socket.end.bind(socket));
+  }).listen(common.PORT, common.localhostIPv4);
+} else if (cluster.isMaster) {
+
+  var connectionDone;
+  var checks = {
+    disconnectedOnClientsEnd: false,
+    workerDied: false
+  };
+
+  // helper function to check if a process is alive
+  var alive = function(pid) {
+    try {
+      process.kill(pid, 0);
+      return true;
+    } catch (e) {
+      return false;
+    }
+  };
+
+  // start worker
+  var worker = cluster.fork();
+
+  // Disconnect worker when it is ready
+  worker.once('listening', function() {
+    net.createConnection(common.PORT, common.localhostIPv4, function() {
+      var socket = this;
+      setTimeout(function() {
+        worker.disconnect();
+        setTimeout(function() {
+          socket.write('.');
+          connectionDone = true;
+        }, 1000);
+      }, 1000);
+    });
+  });
+
+  // Check worker events and properties
+  worker.once('disconnect', function() {
+    checks.disconnectedOnClientsEnd = connectionDone;
+  });
+
+  // Check that the worker died
+  worker.once('exit', function() {
+    checks.workerDied = !alive(worker.process.pid);
+    process.nextTick(function() {
+      process.exit(0);
+    });
+  });
+
+  process.once('exit', function() {
+    assert.ok(checks.disconnectedOnClientsEnd, 'The worker disconnected before all clients are ended');
+    assert.ok(checks.workerDied, 'The worker did not die');
+  });
+}