[wip] ZENKO-1520 stub for prom metrics endpoint in HealthProbeServer

lib/network/probe/HealthProbeServer.js

@@ -24,10 +24,6 @@ function sendSuccess(res, log, msg) {
     res.end(message);
 }
 
-function constructEndpoints(ns, path) {
-    return `/${ns}/${path}`;
-}
-
 function checkStub(log) { // eslint-disable-line
     return true;
 }
@@ -38,17 +34,14 @@ class HealthProbeServer extends httpServer {
         super(params.port, logging);
         this.logging = logging;
         this.setBindAddress(params.bindAddress || 'localhost');
-        this._namespace = params.namespace || '_/health';
-        const livenessURI = constructEndpoints(this._namespace,
-            params.livenessURI || 'liveness');
-        const readinessURI = constructEndpoints(this._namespace,
-            params.readinessURI || 'readiness');
         // hooking our request processing function by calling the
         // parent's method for that
         this.onRequest(this._onRequest);
-        this._reqHandlers = {};
-        this._reqHandlers[livenessURI] = this._onLiveness.bind(this);
-        this._reqHandlers[readinessURI] = this._onReadiness.bind(this);
+        this._reqHandlers = {
+            '/_/health/liveness': this._onLiveness.bind(this),
+            '/_/health/readiness': this._onReadiness.bind(this),
+            '/_/monitoring/metrics': this._onMetrics.bind(this),
+        };
         this._livenessCheck = params.livenessCheck || checkStub;
         this._readinessCheck = params.readinessCheck || checkStub;
     }
@@ -68,8 +61,7 @@ class HealthProbeServer extends httpServer {
         if (req.method !== 'GET') {
             sendError(res, log, errors.MethodNotAllowed);
         }
-        if (req.url.startsWith(`/${this._namespace}`) &&
-            req.url in this._reqHandlers) {
+        if (req.url in this._reqHandlers) {
             this._reqHandlers[req.url](req, res, log);
         } else {
             sendError(res, log, errors.InvalidURI);
@@ -92,6 +84,14 @@ class HealthProbeServer extends httpServer {
         }
     }
 
+    _onMetrics(req, res, log) {
+        log.debug('metrics request received');
+        res.writeHead(200);
+        res.end(
+            '# HELP lifecycle_batches Number of lifecycle batches started\n' +
+                '# TYPE lifecycle_batches counter\n' +
+                'lifecycle_batches 42\n');
+    }
 }
 
 module.exports = HealthProbeServer;