This example creates a simple web service development environment setup using nodejs
- You must have node js installed
- You must have
expressinstalled by:npm install express - You must have Docker installed and running in your machine
Create your project directory(for me it is docker_node, you may choose yours):
$ mkdir docker_node
$ cd docker_nodeCreate the packge.json file with the following content:
$ cat package.json
{
"name": "HelloWorld",
"version": "1.0.0",
"description": "My hello world app",
"author": "Dipanjan Bhowmik",
"license": "ISC",
"main": "server.js",
"scripts": {
"start": "node server.js",
"dev": "nodemon server.js"
},
"dependencies": {
"express": "^4.13.3"
}
}Create the simple web service script server.js:
$ cat server.js
'use strict';
const express = require('express');
var os = require("os");
var hostname = os.hostname();
// Constants
const PORT = 3000;
// App
const app = express();
app.get('/', function (req, res) {
res.send('Hello world\n');
});
app.get('/console/:user', function (req, res) {
var date = new Date();
var response = `Hello ${req.params.user} from ${hostname} at ${date}\n
`;
res.send(response);
});
app.get('/web/:user', function (req, res) {
var date = new Date();
var bgcolor = "#FFFFFF"
if (/[a-f][0-9]+/.test(hostname)) {
bgcolor = `#${hostname.slice(0, 6)}`;
}
var response = `<html>
<body bgcolor="${bgcolor}">
<h2>Hello ${req.params.user}!</h2>
<h3>I am running on: ${hostname}</h3>
<h3>Current time: ${date} </h3>
</body>
</html>
`;
res.send(response);
});
app.listen(PORT);
console.log('Running on http://localhost:' + PORT);Run the Web Service using npm start:
$ npm start
> HelloWorld@1.0.0 start
$HOME/docker-node
> node server.js
Running on http://localhost:3000Now, test it using curl from another terminal. Notice my hostname cirrus is shown for the second request:
$ curl -i localhost:3000
HTTP/1.1 200 OK
X-Powered-By: Express
Content-Type: text/html; charset=utf-8
Content-Length: 12
ETag: W/"c-8O9wgeFTmsAO9bdhtPsBsw"
Date: Thu, 27 Oct 2016 06:12:03 GMT
Connection: keep-alive
Hello world
$ curl -i localhost:3000/console/dipanjan
HTTP/1.1 200 OK
X-Powered-By: Express
Content-Type: text/html; charset=utf-8
Content-Length: 26
ETag: W/"1a-tXiFts4+U6jA7QRVqjOrOQ"
Date: Thu, 27 Oct 2016 06:12:14 GMT
Connection: keep-alive
Hello dipanjan from dream at Wed Apr 17 2019 11:37:25 GMT+0000 (UTC)Congratualations! Your nodejs based web service is up and running.
Our next step is dockerize your web service so that you can run the same in the docker containers.
Please note docker need to be installed and running in your machine.
First, create a file in the project directory named Dockerfile.
$ cat Dockerfile
FROM mhart/alpine-node:6
WORKDIR /app
ADD . /app
EXPOSE 3000
ENTRYPOINT [ "npm", "start" ]Now, build the docker image. I have given the image name as node-test, you can give yours. It will take a while to build that and you need internet connection as the layers will be downloaded from the internet:
$ docker build -t node-demo .
Sending build context to Docker daemon 2.126MB
Step 1/5 : FROM mhart/alpine-node:6
6: Pulling from mhart/alpine-node
5a3ea8efae5d: Pull complete
b4e7bd7dea94: Pull complete
...
Successfully built 042e2add96c7
Successfully tagged node-demo:latestNext, start the docker as a daemon and we have bound 3000 port which will respond with the docker container id(for my test it was 042e2add96c7..):
$ docker run -p5000:3000 -d node-demo
1ce0575a528And test with the same curl command as earlier:
$ curl -i localhost:3000/console/dipanjan
HTTP/1.1 200 OK
X-Powered-By: Express
Content-Type: text/html; charset=utf-8
Content-Length: 77
ETag: W/"4d-KPkGFKjCU+7Z5vR0H4a1HuhWNuw"
Date: Wed, 17 Apr 2019 11:37:25 GMT
Connection: keep-alive
Hello dipanjan from 51368a110da3 at Wed Apr 17 2019 11:37:25 GMT+0000 (UTC)Note that the hostname is also same as first digits of the docker container id.
Finally, to stop the docker container use docker stop:
$ docker stop 1ce0575a528
1ce0575a528Please note if you are making any changes in the file here you need to run the docker build command again to build the image and then run it.
So far so good and your have successfully dockerized your webservice.
You must have noticed that you need to build the docker image every time you make a change in the project file - effectively change > stop > build > start cycle - which is annoying and slows down your pace of development.
First, we will create a separate Dockerfile for our development named Dockerfile.devel.
FROM mhart/alpine-node:6
RUN npm install -g express nodemon
WORKDIR /app
EXPOSE 3000
ENTRYPOINT [ "npm", "run", "dev" ]Create the docker image for the development.
$ docker build -t node-dev -f Dockerfile.devel .
...
And make the changes in the server.js (just change the string Hello to Hi) and without building, we will stop the docker container and start with the following command.
docker run -p5000:3000 -v $PWD:/app -d node-devSo, we have added the volume which is the current directory and mapped it to the /app directory in the docker container.
Now, for once run the stop > build > run cycle. And then if you change the file server.js - you do not need to do the stop > build > run cycle.
So, now you are in a better productive development environment.
Till now the repository was local. Now, we will push our docker image to the public docker repository. For that, you need to create an account in dockerhub.com. My account in dockerhub is onlydevelop. So, all examples will be with that name.
First, you need to see the list of images:
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
node-demo latest ceb718e9ce8b 6 days ago 43.39 MBThen, you tag the image and see if the image is properly tagged:
$ docker tag ceb718e9ce8b onlydevelop/node-test:latest
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
node-demo latest ceb718e9ce8b 6 days ago 43.39 MB
onlydevelop/node-demo latest ceb718e9ce8b 6 days ago 43.39 MBNext, you login and push your docker image to dockerhub:
$ docker login
Login with your Docker ID to push and pull images from Docker Hub. If you don't have a Docker ID, head over to https://hub.docker.com to create one.
Username: onlydevelop
Password:
Login Succeeded
$ docker push onlydevelop/node-demo
The push refers to a repository [docker.io/onlydevelop/node-demo]
01ae0e045d3d: Pushed
15784ea9704c: Pushed
37a679f0fad0: Pushed
3cccad12f85b: Pushed
011b303988d2: Mounted from library/alpine
latest: digest: ...Now, to test it, remove your existing docker images and pull from the repo:
$ docker rmi -f ceb718e9ce8b
...
$ docker run -p5000:3000 -v $PWD:/app -d onlydevelop/node-demo
Unable to find image 'onlydevelop/node-demo:latest' locally
latest: Pulling from onlydevelop/node-demo
...
c7795799ecc7e618So, now your image is pulled from public dockerhub and run in your local machine.
As a pre-requisite, we will us the node-demo image.
So, build docker and push with a version number:
$ docker build -t node-test:0.1 .
Sending build context to Docker daemon 9.868 MB
Step 1 : FROM alpine
---> baa5d63471ea
Step 2 : RUN apk update && apk upgrade
---> Using cache
---> 947cf5948524
...
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
node-test 0.1 326a7eca6110 52 minutes ago 51.18 MB
$ docker tag 326a7eca6110 onlydevelop/node-test:0.1
[14:56]~/work/anvil/node/docker-node:master ✗ $ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
node-test 0.1 326a7eca6110 53 minutes ago 51.18 MB
onlydevelop/node-test 0.1 326a7eca6110 53 minutes ago 51.18 MB
$ docker login
...
$ docker push onlydevelop/node-test:0.1
...Now, we want to test our service in a minikube/kubectl cluster locally. Please check the documentation how can you install minikube/kubectl locally in your machine.
When you are done, first you need to start minikube:
$ minikube start
There is a newer version of minikube available (v0.12.2). Download it here:
https://github.com/kubernetes/minikube/releases/tag/v0.12.2
To disable this notification, add WantUpdateNotification: False to the json config file at /Users/dbhowmik/.minikube/config
(you may have to create the file config.json in this folder if you have no previous configuration)
Starting local Kubernetes cluster...
Kubectl is now configured to use the cluster.You may start the kubectl dashboard using:
$ minikube dashboard
Opening kubernetes dashboard in default browser...Now, we will start a pod as a single instance of our image:
$ kubectl run node-test --image=onlydevelop/node-test:0.1 --port=3000
deployment "node-test" created
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
node-test-253544039-omvfj 1/1 Running 0 1mNow, we need to expose it as a service so that it can be used from outside:
$ kubectl expose deployment node-test --type=NodePort
service "node-test" exposed
$ kubectl get services
NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes 10.0.0.1 <none> 443/TCP 10d
node-test 10.0.0.23 <nodes> 3000/TCP 1mThe --type for minikube supports NodePort only.
Now, we need to know how to get the URL where the service is exposed:
$ minikube service node-test --url
http://192.168.99.100:31815So, now we can use the URL to test our exposed service:
$ curl $(minikube service node-test --url)/user/dipanjan
Hello dipanjan from node-test-253544039-omvfjGreat! That means, the service is exposed properly for single instance.
Now, let us delete this provision:
$ kubectl delete service,deployment node-test
service "node-test" deleted
deployment "node-test" deletedOK. Next, let us run this in a cluster, which is very easy.
Let us create a cluster of 3 replics(note now there are 3 pods):
$ kubectl run node-test --image=onlydevelop/node-test:0.1 --port=3000 --replicas=3
deployment "node-test" created
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
node-test-253544039-gy49t 1/1 Running 0 49s
node-test-253544039-ktx5q 1/1 Running 0 49s
node-test-253544039-pcm4v 1/1 Running 0 49sNow, we will once again expose the service:
$ kubectl expose deployment node-test --type=NodePort
service "node-test" exposed
$ kubectl get services
NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes 10.0.0.1 <none> 443/TCP 10d
node-test 10.0.0.163 <nodes> 3000/TCP 6s
$ minikube service node-test --url
http://192.168.99.100:32062Now, if you run the same curl command multiple times you will response may come from different pods:
$ curl $(minikube service node-test --url)/user/db
Hello db from node-test-253544039-gy49t
$ curl $(minikube service node-test --url)/user/db
Hello db from node-test-253544039-pcm4v
curl $(minikube service node-test --url)/user/db
Hello db from node-test-253544039-ktx5qThis shows now your service is deployed in a load balanced cluster and any one of the host may respond to your request (note the changes in the hostname part after from).
Finally, if you want to cleanup your environment:
$ kubectl delete service,deployment node-test
service "node-test" deleted
deployment "node-test" deleted
$ minikube stop
Stopping local Kubernetes cluster...
Machine stopped.