used prom-client lib to expose custom metrics

Dockerfile

@@ -3,7 +3,7 @@ FROM node
 WORKDIR /app
 
 # Copying npm config file setting npm repository location.
-COPY .npmrc .npmrc
+# COPY .npmrc .npmrc
 
 # If you add the package.json first and run npm install later,
 # Docker won’t have to install the dependencies again if you

app.js

@@ -12,17 +12,16 @@ const libCounter = new Prometheus.Counter({
   help: 'A simple counter for app access during runtime created with unofficial prometheus nodejs library'
 });
 
-const libUptime = new Prometheus.Histogram({
+const libUptime = new Prometheus.Counter({
   name:  'lib_upTime',
-  help: 'uptime A counter of the application\'s uptime in millisenconds.'
+  help: 'uptime A counter of the application\'s uptime in seconds.'
 })
 
-libUptime.startTimer();
 
-const collectDefaultMetrics = Prometheus.collectDefaultMetrics;
+// const collectDefaultMetrics = Prometheus.collectDefaultMetrics;
 
 // Probe every 5th second.
-collectDefaultMetrics({ timeout: 5000 });
+// collectDefaultMetrics({ timeout: 5000 });
 
 // new schema model object based on the structure of what I want to put on MongoDB collection
 var testSchema = new Schema({
@@ -48,9 +47,11 @@ app.get('/metrics', function(req, res){
   // res.write('# HELP invocation_count A simple counter for app access during runtime' + '\n');
   // res.write('# TYPE invocation_count counter'+ '\n');
   // res.write('invocation_count ' + counter + '\n');
+  libUptime.inc(Math.floor(process.uptime()));
   res.set('Content-Type', Prometheus.register.contentType)
   res.end(Prometheus.register.metrics())
   res.end();
+  libUptime.reset();
 });