testing socket availability before attempting to bind

loader.js

@@ -220,11 +220,15 @@ function killWorkers() {
 	});
 }
 
-Loader.notifyWorkers = function (msg, worker_pid) {
+Loader.notifyWorkers = function(msg, worker_pid) {
 	worker_pid = parseInt(worker_pid, 10);
 	workers.forEach(function(worker) {
 		if (parseInt(worker.pid, 10) !== worker_pid) {
-			worker.send(msg);
+			try {
+				worker.send(msg);
+			} catch (e) {
+				console.log('[cluster/notifyWorkers] Failed to reach pid ' + worker_pid);
+			}
 		}
 	});
 };

src/webserver.js

@@ -18,7 +18,8 @@ var path = require('path'),
 	routes = require('./routes'),
 	emitter = require('./emitter'),
 
-	helpers = require('./../public/src/helpers')();
+	helpers = require('./../public/src/helpers')(),
+	net;
 
 if(nconf.get('ssl')) {
 	server = require('https').createServer({
@@ -104,14 +105,9 @@ if(nconf.get('ssl')) {
 			bind_address = ((nconf.get('bind_address') === "0.0.0.0" || !nconf.get('bind_address')) ? '0.0.0.0' : nconf.get('bind_address')) + ':' + port,
 			oldUmask;
 
-		// Alter umask if necessary
-		if (isSocket) {
-			oldUmask = process.umask('0000');
-		}
-
 		args.push(function(err) {
 			if (err) {
-				winston.info('NodeBB was unable to listen on: ' + bind_address);
+				winston.info('[startup] NodeBB was unable to listen on: ' + bind_address);
 				return callback(err);
 			}
 
@@ -123,7 +119,47 @@ if(nconf.get('ssl')) {
 			callback();
 		});
 
-		server.listen.apply(server, args);
+		// Alter umask if necessary
+		if (isSocket) {
+			oldUmask = process.umask('0000');
+			net = require('net');
+			module.exports.testSocket(port, function(err) {
+				if (!err) {
+					server.listen.apply(server, args);
+				} else {
+					winston.error('[startup] NodeBB was unable to secure domain socket access (' + port + ')');
+					winston.error('[startup] ' + err.message);
+					process.exit();
+				}
+			});
+		} else {
+			server.listen.apply(server, args);
+		}
+	};
+
+	module.exports.testSocket = function(socketPath, callback) {
+		async.series([
+			function(next) {
+				fs.exists(socketPath, function(exists) {
+					if (exists) {
+						next();
+					} else {
+						callback();
+					}
+				});
+			},
+			function(next) {
+				var testSocket = new net.Socket();
+				testSocket.on('error', function(err) {
+					next(err.code !== 'ECONNREFUSED' ? err : null);
+				});
+				testSocket.connect({ path: socketPath }, function() {
+					// Something's listening here, abort
+					callback(new Error('port-in-use'));
+				});
+			},
+			async.apply(fs.unlink, socketPath),	// The socket was stale, kick it out of the way
+		], callback);
 	};
 
 }(WebServer));