Exporting metrics for node.js, express, router, and codimd realtime status.

1. **/metrics/router** : exporting node.js/express Prometheus metrics by
[prometheus-api-metrics](https://www.npmjs.com/package/prometheus-api-metrics)

2. **/metrics/codimd** : exporting codimd realtime status (/status) as
Prometheus metrics

Signed-off-by: tarlety <[email protected]>

Author: tarlety

app.js

@@ -17,6 +17,7 @@ var passportSocketIo = require('passport.socketio')
 var helmet = require('helmet')
 var i18n = require('i18n')
 var flash = require('connect-flash')
+var apiMetrics = require('prometheus-api-metrics')
 
 // core
 var config = require('./lib/config')
@@ -56,6 +57,12 @@ function createHttpServer () {
 var app = express()
 var server = createHttpServer()
 
+// API and process monitoring with Prometheus for Node.js micro-service
+app.use(apiMetrics({
+  metricsPath: "/metrics/router",
+  excludeRoutes: ["/metrics/codimd"]
+}))
+
 // logger
 app.use(morgan('combined', {
   stream: logger.stream

lib/routes.js

@@ -28,6 +28,7 @@ appRouter.get('/404', errorPageController.errorNotFound)
 appRouter.get('/500', errorPageController.errorInternalError)
 
 appRouter.get('/status', wrap(statusController.getStatus))
+appRouter.get('/metrics/codimd', wrap(statusController.getMetrics))
 appRouter.get('/config', statusController.getConfig)
 
 // register auth module

lib/status/index.js

@@ -14,6 +14,17 @@ exports.getStatus = async (req, res) => {
   res.send(data)
 }
 
+exports.getMetrics = async (req, res) => {
+  const data = await realtime.getStatus()
+
+  res.set({
+    'Cache-Control': 'private', // only cache by client
+    'X-Robots-Tag': 'noindex, nofollow', // prevent crawling
+    'Content-Type': 'text/plain; charset=utf-8'
+  })
+  res.render('../js/lib/common/metrics.ejs', data)
+}
+
 exports.getConfig = (req, res) => {
   const data = {
     domain: config.domain,

package-lock.json

@@ -86,6 +86,8 @@
     "passport.socketio": "~3.7.0",
     "pg": "~6.1.2",
     "pg-hstore": "~2.3.2",
+    "prom-client": "^12.0.0",
+    "prometheus-api-metrics": "^2.2.5",
     "randomcolor": "~0.5.4",
     "readline-sync": "~1.4.7",
     "request": "~2.88.0",

package.json

@@ -0,0 +1,11 @@
+online_notes <%- onlineNotes %>
+online_users <%- onlineUsers %>
+distinct_online_users <%- distinctOnlineUsers %>
+notes_count <%- notesCount %>
+registered_users <%- registeredUsers %>
+online_registered_users <%- onlineRegisteredUsers %>
+distinct_online_registered_users <%- distinctOnlineRegisteredUsers %>
+is_connection_busy <%- isConnectionBusy ? 1 : 0 %>
+connection_socket_queue_length <%- connectionSocketQueueLength %>
+is_disconnect_busy <%- isDisconnectBusy ? 1: 0 %>
+disconnect_socket_queue_length <%- disconnectSocketQueueLength %>