I have a container based application running node JS and my backend is a mongoDB container.
Basically, what I am planning to do is to run this in kubernetes.
I have deployed this as separate containers on my current environment and it works fine. I have a mongoDB container and a node JS container.
To connect the two I would do
docker run -d --link=mongodb:mongodb -e MONGODB_URL='mongodb://mongodb:27017/user' -p 4000:4000 e922a127d049
my connection.js runs as below where it would take the MONGODB_URL and pass into the process.env in my node JS container. My connection.js would then extract the MONGODB_URL into the mongoDbUrl as show below.
const mongoClient = require('mongodb').MongoClient;
const mongoDbUrl = process.env.MONGODB_URL;
//console.log(process.env.MONGODB_URL)
let mongodb;
function connect(callback){
mongoClient.connect(mongoDbUrl, (err, db) => {
mongodb = db;
callback();
});
}
function get(){
return mongodb;
}
function close(){
mongodb.close();
}
module.exports = {
connect,
get,
close
};
To deploy on k8s, I have written a yaml file for
1) web controller 2) web service 3) mongoDB controller 4) mongoDB service
This is my current mongoDB controller
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: mongo-deployment
spec:
replicas: 1
template:
metadata:
labels:
name: mongo
spec:
containers:
- image: mongo:latest
name: mongo
ports:
- name: mongo
containerPort: 27017
hostPort: 27017
my mongoDB service
apiVersion: v1
kind: Service
metadata:
labels:
name: mongodb
name: mongodb
spec:
ports:
- port: 27017
targetPort: 27017
selector:
name: mongo
my web controller
apiVersion: v1
kind: ReplicationController
metadata:
labels:
name: web
name: web-controller
spec:
replicas: 1
selector:
name: web
template:
metadata:
labels:
name: web
spec:
containers:
- image: leexha/node_demo:21
env:
- name: MONGODB_URL
value: "mongodb://mongodb:27017/user"
name: web
ports:
- containerPort: 4000
name: node-server
and my web service
apiVersion: v1
kind: Service
metadata:
name: web
labels:
name: web
spec:
type: NodePort
ports:
- port: 4000
targetPort: 4000
protocol: TCP
selector:
name: web
I was able to deploy all the services and pods on my local kubernetes cluster.
However, when I tried to access the web application over a nodeport, it tells me that there is a connection error to my mongoDB.
TypeError: Cannot read property 'collection' of null
at /app/app.js:24:17
at Layer.handle [as handle_request]
This is my node JS code for app.js
var bodyParser = require('body-parser')
, MongoClient = require('mongodb').MongoClient
, PORT = 4000
, instantMongoCrud = require('express-mongo-crud') // require the module
, express = require('express')
, app = express()
, path = require('path')
, options = { //specify options
host: `localhost:${PORT}`
}
, db = require('./connection')
// connection to database
db.connect(() => {
app.use(bodyParser.json()); // add body parser
app.use(bodyParser.urlencoded({ extended: true }));
//console.log('Hello ' + process.env.MONGODB_URL)
// get function
app.get('/', function(req, res) {
db.get().collection('users').find({}).toArray(function(err, data){
if (err)
console.log(err)
else
res.render('../views/pages/index.ejs',{data:data});
});
});
Clearly, this is an error when my node JS application is unable to read the mongoDB service.
I at first thought my MONGODB_URL was not set in my container. However, when I checked the nodeJS container using
kubectl exec -it web-controller-r269f /bin/bash
and echo my MONGODB_URL it returned me back mongodb://mongodb:27017/user which is correct.
Im quite unsure what I am doing wrong as I am pretty sure I have done everything in order and my web deployment is communicating to mongoDB service. Any help? Sorry am still learning kubernetes and please pardon any mistakes
