Merge pull request #76 from microservices-demo/prometheus-metrics

Prometheus metrics in the front-end

api/metrics/index.js

@@ -0,0 +1,61 @@
+(function (){
+  'use strict';
+
+  var express = require("express")
+    , client  = require('prom-client')
+    , app     = express()
+
+  const metric = {
+    http: {
+      requests: {
+        duration: new client.Summary('request_duration_seconds', 'request duration in seconds', ['method', 'path', 'status']),
+      }
+    }
+  }
+
+  function s(start) {
+    var diff = process.hrtime(start);
+    return (diff[0] * 1e9 + diff[1]) / 1000000000;
+  }
+
+  function parse(path) {
+    var clean_path = path;
+
+    if (path[path.length - 1] != '/') {
+      if (!path.includes('.')) {
+        clean_path = path.substr(0, path.lastIndexOf('/') + 1);
+      }
+    };
+
+    return clean_path;
+}
+
+  function observe(method, path, statusCode, start) {
+    var path = path.toLowerCase();
+    if (path !== '/metrics' && path !== '/metrics/') {
+        var duration = s(start);
+        var method = method.toLowerCase();
+        var clean_path = parse(path);
+        metric.http.requests.duration.labels(method, clean_path, statusCode).observe(duration);
+    }
+  };
+
+  function middleware(request, response, done) {
+    var start = process.hrtime();
+
+    response.on('finish', function() {
+      observe(request.method, request.path, response.statusCode, start);
+    });
+
+    return done();
+  };
+
+
+  app.use(middleware);
+  app.get("/metrics", function(req, res) {
+      res.header("content-type", "text/plain");
+      return res.end(client.register.metrics())
+  });
+
+  module.exports = app;
+}());

helpers/index.js

@@ -11,6 +11,7 @@
    * var app = express();
    * app.use(helpers.errorHandler);
    * */
+
   helpers.errorHandler = function(err, req, res, next) {
     var ret = {
       message: err.message,

package.json

@@ -26,8 +26,7 @@
     "finalhandler": "^0.4.1",
     "request": "^2.72.0",
     "serve-static": "^1.10.2",
-    "epimetheus": "^1.0.46",
-    "prom-client": "^6.1.0",
+    "prom-client": "^6.3.0",
     "morgan": "^1.7.0",
     "connect-redis": "^3.2.0"
   },

server.js

@@ -6,18 +6,17 @@ var request      = require("request")
   , async        = require("async")
   , cookieParser = require("cookie-parser")
   , session      = require("express-session")
-  , epimetheus   = require("epimetheus")
   , config       = require("./config")
   , helpers      = require("./helpers")
   , cart         = require("./api/cart")
   , catalogue    = require("./api/catalogue")
   , orders       = require("./api/orders")
   , user         = require("./api/user")
+  , metrics      = require("./api/metrics")
   , app          = express()
 
-epimetheus.instrument(app);
-
 app.use(express.static("public"));
+app.use(metrics);
 if(process.env.SESSION_REDIS) {
     console.log('Using the redis based session manager');
     app.use(session(config.session_redis));
@@ -29,7 +28,6 @@ else {
 
 app.use(bodyParser.json());
 app.use(cookieParser());
-app.use(helpers.errorHandler);
 app.use(helpers.sessionMiddleware);
 app.use(morgan("dev", {}));
 
@@ -50,6 +48,8 @@ app.use(catalogue);
 app.use(orders);
 app.use(user);
 
+app.use(helpers.errorHandler);
+
 var server = app.listen(process.env.PORT || 8079, function () {
   var port = server.address().port;
   console.log("App now running in %s mode on port %d", app.get("env"), port);