Push scalability (#3080)

* Update status through increment
* adds support for incrementing nested keys
* fix issue when having spaces in keys for ordering
* Refactors PushController to use worker
* Adds tests for custom push queue config
* Makes PushController adapter independant
* Better logging of _PushStatus in VERBOSE

src/Adapters/MessageQueue/EventEmitterMQ.js

@@ -0,0 +1,65 @@
+import events from 'events';
+
+const emitter = new events.EventEmitter();
+const subscriptions = new Map();
+
+function unsubscribe(channel: string) {
+  if (!subscriptions.has(channel)) {
+    //console.log('No channel to unsub from');
+    return;
+  }
+  //console.log('unsub ', channel);
+  emitter.removeListener(channel, subscriptions.get(channel));
+  subscriptions.delete(channel);
+}
+
+class Publisher {
+  emitter: any;
+
+  constructor(emitter: any) {
+    this.emitter = emitter;
+  }
+
+  publish(channel: string, message: string): void {
+    this.emitter.emit(channel, message);
+  }
+}
+
+class Consumer extends events.EventEmitter {
+  emitter: any;
+
+  constructor(emitter: any) {
+    super();
+    this.emitter = emitter;
+  }
+
+  subscribe(channel: string): void {
+    unsubscribe(channel);
+    const handler = (message) => {
+      this.emit('message', channel, message);
+    }
+    subscriptions.set(channel, handler);
+    this.emitter.on(channel, handler);
+  }
+
+  unsubscribe(channel: string): void {
+    unsubscribe(channel);
+  }
+}
+
+function createPublisher(): any {
+  return new Publisher(emitter);
+}
+
+function createSubscriber(): any {
+  return new Consumer(emitter);
+}
+
+const EventEmitterMQ = {
+  createPublisher,
+  createSubscriber
+}
+
+export {
+  EventEmitterMQ
+}