A simple web app written in Node.js that you can use for testing.
It reads in an env variable TARGET
and prints "Hello ${TARGET}!". If
TARGET is not specified, it will use "World" as the TARGET.
- A Kubernetes cluster with Knative installed. Follow the installation instructions if you need to create one.
- Docker installed and running on your local machine, and a Docker Hub account configured (we'll use it for a container registry).
- Node.js installed and configured.
While you can clone all of the code from this directory, hello world apps are generally more useful if you build them step-by-step. The following instructions recreate the source files from this folder.
-
Create a new directory and initalize
npm
. You can accept the defaults, but change the entry point toapp.js
to be consistent with the sample code here.npm init package name: (helloworld-nodejs) version: (1.0.0) description: entry point: (index.js) app.js test command: git repository: keywords: author: license: (ISC) Apache-2.0
-
Install the
express
package:npm install express --save
-
Create a new file named
app.js
and paste the following code:const express = require('express'); const app = express(); app.get('/', function (req, res) { console.log('Hello world received a request.'); const target = process.env.TARGET || 'World'; res.send('Hello ' + target + '!'); }); const port = process.env.PORT || 8080; app.listen(port, function () { console.log('Hello world listening on port', port); });
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Modify the
package.json
file to add a start command to the scripts section:{ "name": "knative-serving-helloworld", "version": "1.0.0", "description": "", "main": "app.js", "scripts": { "start": "node app.js" }, "author": "", "license": "Apache-2.0" }
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In your project directory, create a file named
Dockerfile
and copy the code block below into it. For detailed instructions on dockerizing a Node.js app, see Dockerizing a Node.js web app.# Use the official Node 8 image. # https://hub.docker.com/_/node FROM node:8 # Create and change to the app directory. WORKDIR /usr/src/app # Copy application dependency manifests to the container image. # A wildcard is used to ensure both package.json AND package-lock.json are copied. # Copying this separately prevents re-running npm install on every code change. COPY package*.json ./ # Install production dependencies. RUN npm install --only=production # Copy local code to the container image. COPY . . # Configure and document the service HTTP port. ENV PORT 8080 EXPOSE $PORT # Run the web service on container startup. CMD [ "npm", "start" ]
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Create a new file,
service.yaml
and copy the following service definition into the file. Make sure to replace{username}
with your Docker Hub username.apiVersion: serving.knative.dev/v1alpha1 kind: Service metadata: name: helloworld-nodejs namespace: default spec: runLatest: configuration: revisionTemplate: spec: container: image: docker.io/{username}/helloworld-nodejs env: - name: TARGET value: "Node.js Sample v1"
Once you have recreated the sample code files (or used the files in the sample folder) you're ready to build and deploy the sample app.
-
Use Docker to build the sample code into a container. To build and push with Docker Hub, run these commands replacing
{username}
with your Docker Hub username:# Build the container on your local machine docker build -t {username}/helloworld-nodejs . # Push the container to docker registry docker push {username}/helloworld-nodejs
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After the build has completed and the container is pushed to docker hub, you can deploy the app into your cluster. Ensure that the container image value in
service.yaml
matches the container you built in the previous step. Apply the configuration usingkubectl
:kubectl apply --filename service.yaml
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Now that your service is created, Knative will perform the following steps:
- Create a new immutable revision for this version of the app.
- Network programming to create a route, ingress, service, and load balance for your app.
- Automatically scale your pods up and down (including to zero active pods).
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To find the IP address for your service, use
kubectl get svc knative-ingressgateway --namespace istio-system
to get the ingress IP for your cluster. If your cluster is new, it may take sometime for the service to get asssigned an external IP address.kubectl get svc knative-ingressgateway --namespace istio-system NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE knative-ingressgateway LoadBalancer 10.23.247.74 35.203.155.229 80:32380/TCP,443:32390/TCP,32400:32400/TCP 2d
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To find the URL for your service, use
kubectl get ksvc helloworld-nodejs --output=custom-columns=NAME:.metadata.name,DOMAIN:.status.domain NAME DOMAIN helloworld-nodejs helloworld-nodejs.default.example.com
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Now you can make a request to your app to see the result. Replace
{IP_ADDRESS}
with the address you see returned in the previous step.curl -H "Host: helloworld-nodejs.default.example.com" http://{IP_ADDRESS} Hello World: NOT SPECIFIED
To remove the sample app from your cluster, delete the service record:
kubectl delete --filename service.yaml