Add prom-client and export Node.js metrics

zubron · May 21, 2018 · 0f4125f · 0f4125f
1 parent b5179e8
commit 0f4125f
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Showing 6 changed files with 62 additions and 2 deletions.
diff --git a/README.md b/README.md
@@ -36,3 +36,13 @@ Then, follow the [`prometheus` README](./prometheus/README.md) to verify that yo
 provided configuration.
 
 Having problems? Please open an issue in this project :)
+
+### S1
+
+In this branch, we add support for exporting Prometheus metrics from the
+API in `todo-app`.
+
+See the [`todo-app` README](./todo-app/README.md) for more details.
+
+These metrics can be queried within the Prometheus UI as our configuration
+already has an [entry for the ToDo API](./prometheus/prometheus.yml)
diff --git a/todo-app/README.md b/todo-app/README.md
@@ -51,3 +51,27 @@ To print only the URL, use the following command:
 ```
 minikube service demo-prom-demo --url
 ```
+
+## S1: Exporting Prometheus metrics
+
+To export Prometheus metrics from our API, we can use a [Prometheus client for Node.js](https://github.com/siimon/prom-client).
+
+We add this client library as a dependency of our project (including it in [`package.json`](./app/package.json)).
+To use the library, we instantiate an instance of it in the code for handling the [API routes](./app/api/routes.js), and use the client to collect default metrics about the Node.js process.
+We then add an additional endpoint to our API (`/metrics`) which, when requested, sends all the metrics our Prometheus client has gathered.
+
+To deploy this code, [build the latest image](#building-the-images).
+The Helm chart contains changes in this branch to use this latest image.
+To update your `helm` deployment use the following command:
+
+```
+helm upgrade demo chart
+```
+
+You can check the status of the deployment using the [previous instructions](#deploying-the-application).
+
+Once the new version has been deployed, you can see the metrics that are being exported by visting:
+
+```
+$(minikube service demo-prom-demo --url)/metrics
+```
diff --git a/todo-app/app/api/routes.js b/todo-app/app/api/routes.js
@@ -1,5 +1,8 @@
 const paths = require('../config/paths');
 const Todo = require('./models/todo');
+const Prometheus = require('prom-client');
+
+Prometheus.collectDefaultMetrics();
 
 const getTodos = (res) => {
     Todo.find((err, todos) => {
@@ -85,6 +88,12 @@ module.exports = (app) => {
         });
     });
 
+    // Export Prometheus metrics
+    app.get('/metrics', (req, res) => {
+        res.set('Content-Type', Prometheus.register.contentType);
+        res.end(Prometheus.register.metrics());
+    });
+
     app.get('/', (req, res) => {
         res.sendFile(paths.staticFiles);
     });

diff --git a/todo-app/app/package.json b/todo-app/app/package.json
@@ -8,6 +8,7 @@
     "body-parser": "^1.18.2",
     "express": "^4.16.3",
     "mongoose": "^5.0.17",
-    "morgan": "^1.9.0"
+    "morgan": "^1.9.0",
+    "prom-client": "^11.0.0"
   }
 }
diff --git a/todo-app/app/yarn.lock b/todo-app/app/yarn.lock
@@ -25,6 +25,10 @@ basic-auth@~2.0.0:
   dependencies:
     safe-buffer "5.1.1"
 
+bintrees@1.0.1:
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/bintrees/-/bintrees-1.0.1.tgz#0e655c9b9c2435eaab68bf4027226d2b55a34524"
+
 bluebird@3.5.0:
   version "3.5.0"
   resolved "https://registry.yarnpkg.com/bluebird/-/bluebird-3.5.0.tgz#791420d7f551eea2897453a8a77653f96606d67c"
@@ -328,6 +332,12 @@ path-to-regexp@0.1.7:
   version "0.1.7"
   resolved "https://registry.yarnpkg.com/path-to-regexp/-/path-to-regexp-0.1.7.tgz#df604178005f522f15eb4490e7247a1bfaa67f8c"
 
+prom-client@^11.0.0:
+  version "11.0.0"
+  resolved "https://registry.yarnpkg.com/prom-client/-/prom-client-11.0.0.tgz#d7e5b58778e04c774de2aa7e4d400552b48713ab"
+  dependencies:
+    tdigest "^0.1.1"
+
 proxy-addr@~2.0.3:
   version "2.0.3"
   resolved "https://registry.yarnpkg.com/proxy-addr/-/proxy-addr-2.0.3.tgz#355f262505a621646b3130a728eb647e22055341"
@@ -443,6 +453,12 @@ statuses@~1.4.0:
   version "1.4.0"
   resolved "https://registry.yarnpkg.com/statuses/-/statuses-1.4.0.tgz#bb73d446da2796106efcc1b601a253d6c46bd087"
 
+tdigest@^0.1.1:
+  version "0.1.1"
+  resolved "https://registry.yarnpkg.com/tdigest/-/tdigest-0.1.1.tgz#2e3cb2c39ea449e55d1e6cd91117accca4588021"
+  dependencies:
+    bintrees "1.0.1"
+
 type-is@~1.6.15, type-is@~1.6.16:
   version "1.6.16"
   resolved "https://registry.yarnpkg.com/type-is/-/type-is-1.6.16.tgz#f89ce341541c672b25ee7ae3c73dee3b2be50194"

diff --git a/todo-app/chart/values.yaml b/todo-app/chart/values.yaml
@@ -4,7 +4,7 @@
 replicaCount: 1
 image:
   repository: todo-demo
-  tag: s0
+  tag: s1
   pullPolicy: IfNotPresent
 service:
   name: todo-app