net: make Server.prototype.unref() persistent

Currently, the unref() method does not remember any state
if called before the server's handle has been created. This
commit adds state to track calls to ref() and unref().

PR-URL: #897
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Brendan Ashworth <brendan.ashworth@me.com>

lib/net.js

@@ -1038,6 +1038,7 @@ function Server(options, connectionListener) {
   this._handle = null;
   this._usingSlaves = false;
   this._slaves = [];
+  this._unref = false;
 
   this.allowHalfOpen = options.allowHalfOpen || false;
   this.pauseOnConnect = !!options.pauseOnConnect;
@@ -1171,6 +1172,10 @@ Server.prototype._listen2 = function(address, port, addressType, backlog, fd) {
   // generate connection key, this should be unique to the connection
   this._connectionKey = addressType + ':' + address + ':' + port;
 
+  // unref the handle if the server was unref'ed prior to listening
+  if (this._unref)
+    this.unref();
+
   process.nextTick(function() {
     // ensure handle hasn't closed
     if (self._handle)
@@ -1440,11 +1445,15 @@ Server.prototype._setupSlave = function(socketList) {
 };
 
 Server.prototype.ref = function() {
+  this._unref = false;
+
   if (this._handle)
     this._handle.ref();
 };
 
 Server.prototype.unref = function() {
+  this._unref = true;
+
   if (this._handle)
     this._handle.unref();
 };

test/parallel/test-net-server-unref-persistent.js

@@ -0,0 +1,20 @@
+var common = require('../common');
+var assert = require('assert');
+var net = require('net');
+var closed = false;
+var server = net.createServer();
+
+// unref before listening
+server.unref();
+server.listen();
+
+// If the timeout fires, that means the server held the event loop open
+// and the unref() was not persistent. Close the server and fail the test.
+setTimeout(function() {
+  closed = true;
+  server.close();
+}, 1000).unref();
+
+process.on('exit', function() {
+  assert.strictEqual(closed, false, 'server should not hold loop open');
+});