net: lazy listen on handler

This allow the server to be shared without the need to handle connection
from master

doc/api/child_process.markdown

@@ -191,8 +191,9 @@ And the child would the recive the server object as:
       }
     });
 
-Note that the server is now shared between the parent and child, this means
-that some connections will be handled by the parent and some by the child.
+Note that the server is now shared between the parent and child. This means
+that any connections will be load balanced between the servers provided there
+is a `connection` listener.
 
 **send socket object**
 

doc/api/net.markdown

@@ -10,6 +10,8 @@ this module with `require('net');`
 
 Creates a new TCP server. The `connectionListener` argument is
 automatically set as a listener for the ['connection'][] event.
+If the server has no `connection` listener it will not accept
+connections until it gets one.
 
 `options` is an object with the following defaults:
 

lib/net.js

@@ -896,18 +896,6 @@ Server.prototype._listen2 = function(address, port, addressType, backlog, fd) {
   var self = this;
   var r = 0;
 
-  // If there is not yet a handle, we need to create one and bind.
-  // In the case of a server sent via IPC, we don't need to do this.
-  if (!self._handle) {
-    self._handle = createServerHandle(address, port, addressType, fd);
-    if (!self._handle) {
-      process.nextTick(function() {
-        self.emit('error', errnoException(errno, 'listen'));
-      });
-      return;
-    }
-  }
-
   self._handle.onconnection = onconnection;
   self._handle.owner = self;
 
@@ -923,15 +911,13 @@ Server.prototype._listen2 = function(address, port, addressType, backlog, fd) {
     process.nextTick(function() {
       self.emit('error', ex);
     });
-    return;
+    return r;
   }
 
   // generate connection key, this should be unique to the connection
   this._connectionKey = addressType + ':' + address + ':' + port;
 
-  process.nextTick(function() {
-    self.emit('listening');
-  });
+  return r;
 };
 
 
@@ -941,10 +927,46 @@ function listen(self, address, port, addressType, backlog, fd) {
   if (cluster.isWorker) {
     cluster._getServer(self, address, port, addressType, fd, function(handle) {
       self._handle = handle;
-      self._listen2(address, port, addressType, backlog, fd);
+      var r = self._listen2(address, port, addressType, backlog, fd);
+      if (r === 0) {
+        self.emit('listening');
+      }
     });
   } else {
-    self._listen2(address, port, addressType, backlog, fd);
+    // If there is not yet a handle, we need to create one and bind.
+    // In the case of a server sent via IPC, we don't need to do this.
+    if (!self._handle) {
+      self._handle = createServerHandle(address, port, addressType, fd);
+      if (!self._handle) {
+        process.nextTick(function() {
+          self.emit('error', errnoException(errno, 'listen'));
+        });
+        return;
+      }
+    }
+
+    // self._handle.listen will be called lazy
+    // if there are no connection listeners
+    if (self.listeners('connection').length === 0) {
+      self.on('newListener', function removeme(name) {
+        if (name !== 'connection') return;
+
+        self.removeListener('newListener', removeme);
+        self._listen2(address, port, addressType, backlog, fd);
+      });
+
+      process.nextTick(function() {
+        self.emit('listening');
+      });
+      return;
+    }
+
+    var r = self._listen2(address, port, addressType, backlog, fd);
+    if (r === 0) {
+      process.nextTick(function() {
+        self.emit('listening');
+      });
+    }
   }
 }
 

test/simple/test-net-lazy-listen.js

@@ -0,0 +1,182 @@
+// 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.
+
+var common = require('../common');
+var net = require('net');
+var fork = require('child_process').fork;
+
+if (process.argv[2] === 'worker') {
+  process.once('disconnect', function () {
+    process.exit(0);
+  });
+
+  process.on('message', function (msg, server) {
+    if (msg !== 'server') return;
+
+    server.on('connection', function (socket) {
+      socket.end(process.argv[3]);
+    });
+
+    process.send('listen');
+  });
+
+  process.send('online');
+  return;
+}
+
+var workers = [];
+
+function spawn(server, id, cb) {
+ // create a worker
+  var worker = fork(__filename, ['worker', id]);
+  workers[id] = worker;
+
+  // wait for ready
+  worker.on('message', function (msg) {
+    switch (msg) {
+      case 'online':
+        worker.send('server', server);
+        break;
+      case 'listen':
+        cb(worker);
+        break;
+      default:
+        throw new Error('got wrong message' + msg);
+    }
+  });
+
+  return worker;
+}
+
+// create a server instance there don't take connections
+var server = net.createServer().listen(common.PORT, function () {
+
+  setTimeout(function() {
+      console.log('spawn worker#0');
+      spawn(server, 0, function () {
+        console.log('worker#0 spawned');
+      });
+  }, 250);
+
+  console.log('testing for standby, expect id 0');
+  testResponse([0], function () {
+
+    // test with two worker, expect id response to be 0 or 1
+    testNewWorker(1, [0, 1], function () {
+
+      // kill worker#0, expect id response to be 1
+      testWorkerDeath(0, [1], function () {
+
+        // close server, expect all connections to continue
+        testServerClose(server, [1], function () {
+
+          // killing worker#1, expect all connections to fail
+          testWorkerDeath(1, [], function () {
+            console.log('test complete');
+          });
+        });
+      });
+    });
+  });
+});
+
+function testServerClose(server, expect, cb) {
+  console.log('closeing server');
+  server.close(function () {
+    testResponse(expect, cb);
+  });
+}
+
+function testNewWorker(workerId, exptect, cb) {
+  console.log('spawning worker#' + workerId);
+  spawn(server, 1, function () {
+    testResponse(exptect, cb);
+  });
+}
+
+function testWorkerDeath(workerID, exptect, cb) {
+  // killing worker#1, expect all connections to fail
+  console.log('killing worker#' + workerID);
+  workers[workerID].kill();
+  workers[workerID].once('exit', function () {
+    testResponse(exptect, cb);
+  });
+}
+
+function testResponse(expect, cb) {
+  // make 25 connections
+  var count = 25;
+  var missing = expect.slice(0);
+
+  var i = count;
+  while (i--) {
+    makeConnection(function (error, id) {
+      if (expect.length === 0) {
+        if (error === null) {
+          throw new Error('connect should not be possible');
+        }
+      } else {
+        if (expect.indexOf(id) === -1) {
+          throw new Error('got unexpected response: ' + id +
+                          ', expected: ' + expect.join(', '));
+        }
+
+        var index = missing.indexOf(id);
+        if (index !== -1) missing.splice(index, 1);
+      }
+
+      count -= 1;
+      if (count === 0) {
+        if (missing.length !== 0) {
+          throw new Error('no connection responsed with the following id: ' +
+                          missing.join(', '));
+        }
+        cb();
+      }
+    });
+  }
+}
+
+function makeConnection(cb) {
+  var client = net.connect({ port: common.PORT });
+
+  var id = null;
+  client.once('data', function(data) {
+    id = parseInt(data, 10);
+  });
+
+  var error = null;
+  client.once('error', function (e) {
+    error = e;
+  });
+
+  client.setTimeout(500);
+
+  client.on('close', function () {
+    cb(error, id);
+  });
+}
+
+process.on('exit', function () {
+  workers.forEach(function (worker) {
+    try { worker.kill(); } catch(e) {}
+  });
+});