improvement(module:metrics): add websocket clients and memory caches

app/metrics.js

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2019 Lime Technology Inc.  All rights reserved.
+ * Written by: Alexis Tyler
+ */
+
+/**
+ * The Graphql pm2 metrics reporters.
+ */
+module.exports = function ($injector) {
+    const websocketClients = {
+        name: 'Websocket clients',
+        value: () => $injector.resolve('ws-clients').size
+    };
+
+    const memoryCaches = {
+        name: 'Memory caches',
+        value: () => {
+            const caches = $injector.resolve('caches');
+            const keys = caches.keys();
+
+            // Return amount of caches that exist
+            return keys.length;
+        }
+    };
+
+    return {
+        websocketClients,
+        memoryCaches
+    };
+}