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Developing microservice apps with the Node.js Express application stack

duration 40 minutes

What you will learn

Application stacks enable the development and optimization of microservice applications. With application stacks, developers don’t need to manage the full software development stack or be experts on underlying container technologies or Kubernetes. Application stacks are customized for specific enterprises to incorporate their company standards and technology choices. Developers access these stacks by configuring their development environment to point to a stack configuration.

In this guide, you’ll learn how to configure your development environment, then create and run a simple cloud native microservice based on the Node.js Express application stack. Finally, you’ll update the microservice that you created and deploy it to Kubernetes or serverless. Deployment to serverless is optional depending on whether you want to Scale to Zero.

Applications in this guide are written based on the Express API specifications, built and run with Node.js, and deployed to Kubernetes through a modern DevOps toolchain that is triggered in Git.

Prerequisites

  • Docker must be installed.
  • Appsody must be installed.
  • Optional: If your organisation has customized application stacks, you need the URL that points to an index.yaml configuration file.
  • Optional: If you are testing multiple microservices together, you must have access to a Kubernetes cluster for development. For local cluster development on Docker Desktop, you can enable Kubernetes from the menu by selecting Preferences -> Kubernetes -> Enable Kubernetes. Other options include Minishift or Minikube. If you want to use remote cluster development, use Codewind.

Getting started

Configuring your development environment

To check the repositories that you can already access, run the following command:

appsody repo list

You see output similar to the following example:

NAME        URL
*incubator https://github.com/appsody/stacks/releases/latest/download/incubator-index.yaml

Next, run the following command to add the URL for your stack configuration file:

appsody repo add <my-org-stack> <URL>

where <my-org-stack> is your chosen repository name and <URL> is the URL for your stack index.yaml configuration file.

Note: If you do not have customized, pre-configured application stacks, you can skip to Initializing your project and develop your app based on the public application stack for Node.js Express.

Check the repositories again by running appsody repo list to see that your repository was added. In the following examples, the repository is called acme-stacks and the URL is https://github.com/acme.inc/stacks/index.yaml:

NAME        URL
*incubator https://github.com/appsody/stacks/releases/latest/download/incubator-index.yaml
acme-stacks https://github.com/acme.inc/stacks/index.yaml

In this example, the asterisk (*) shows that incubator is the default repository. Run the following command to set acme-stacks as the default repository:

appsody repo set-default acme-stacks

Check the available repositories again by running appsody repo list to see that the default is updated:

NAME        URL
incubator https://github.com/appsody/stacks/releases/latest/download/incubator-index.yaml
*acme-stacks https://github.com/acme.inc/stacks/index.yaml

Recommendation: To avoid initializing projects that are based on the public application stacks, it’s best to remove incubator from the list. Run the following command to remove the incubator repository:

appsody repo remove incubator

Check the available repositories again by running appsody repo list to see that incubator is removed:

NAME     	URL
*acme-stacks https://github.com/acme.inc/stacks/index.yaml

Your development environment is now configured to use your customized application stacks. Next, you need to initialize your project.

Initializing your project

First, create a directory that will contain the project:

mkdir -p ~/projects/simple-nodejs-express
cd ~/projects/simple-nodejs-express

Run the following command to initialize your Node.js Express project:

appsody init nodejs-express

The output from the command is similar to the following example:

Downloading nodejs-express template project from https://github.com/appsody/stacks/releases/download/nodejs-express-v0.4.2/incubator.nodejs-express.v0.4.2.templates.simple.tar.gz
Download complete. Extracting files from /Users/user1/appsody/test6/nodejs-express.tar.gz
Setting up the development environment
Your Appsody project name has been set to test6
Pulling docker image docker.io/appsody/nodejs-express:0.4
Running command: docker pull docker.io/appsody/nodejs-express:0.4
0.4: Pulling from appsody/nodejs-express
Status: Downloaded newer image for appsody/nodejs-express:0.4
docker.io/appsody/nodejs-express:0.4
Running command: docker run --rm --entrypoint /bin/bash docker.io/appsody/nodejs-express:0.4 -c find /project -type f -name .appsody-init.sh
Successfully initialized Appsody project with the incubator/nodejs-express stack and the default template.

Your new project is created, built, and started inside a container.

Understanding the project layout

For context, the following image displays the structure of the project that you’re working on:

Project structure

This project contains the following artifacts:

  • app.js, a sample javascript app
  • package-lock.json, a project build file
  • package.json, a project build file
  • test.js, a simple test

Running the development environment

Run the following command to start the development environment:

appsody run

The CLI launches a local Docker image that contains the Node.js Express runtime environment that hosts the microservice. After some time, you see a message similar to the following example:

[Container] Running command:  npm start
[Container]
[Container] > nodejs-express@0.4 start /project
[Container] > node server.js
[Container]
[Container] [Mon Nov 18 10:46:35 2019] com.ibm.diagnostics.healthcenter.loader INFO: Node Application Metrics 5.1.1.201911141807 (Agent Core 4.0.5)
[Container] [Mon Nov 18 10:46:35 2019] com.ibm.diagnostics.healthcenter.mqtt INFO: Connecting to broker localhost:1883
[Container] App started on PORT 3000

This message indicates that the project is started. Browse to http://localhost:3000 and you can see the splash screen.

Browser showing Appsody splash screen

You are now ready to begin developing your application.

Creating and updating the application

You are now going to create a new route that listens on http://localhost:3000/example.

Create a new file called example.js in your project folder and populate it with the following code:

var express = require('express');
var router = express.Router();
/* GET users listing. */
router.get('/', function(req, res, next) {
 res.send('NEW ROUTE LISTENING');
});
module.exports = router;

Save the changes.

Edit the app.js file and update the contents to match the following code:

const app = require('express')()
var exampleRouter = require("./example")
app.get('/', (req, res) => {
 res.send("Hello from Appsody!");
});
app.use("/example", exampleRouter);
module.exports.app = app;

Save the changes.

The development environment watches for file changes and automatically updates your application. Point your browser to http://localhost:3000/example to see your new route, which displays NEW ROUTE LISTENING.

Testing the application

If you are building an application that is composed of microservices, you need to test within the context of the overall system. First, test your application and perform unit testing in isolation. To test the application as part of the system, deploy the system and then the new application.

You can choose how you want to deploy the system and application. If you have adequate CPU and memory to run MiniShift, the application, and the associated services, then you can deploy the application on a local Kubernetes that is running on your computer. Alternatively, you can enable Docker Desktop for Kubernetes, which is described in the Prerequisites section of the guide.

You can also deploy the system, application, and the associated services in a private namespace on a development cluster. From this private namespace, you can commit the microservices in Git repositories and deploy them through a DevOps pipeline, not directly to Kubernetes.

Testing locally on Kubernetes

After you finish writing your application code, the CLI makes it easy to deploy directly to a Kubernetes cluster for further local testing. The ability to deploy directly to a Kubernetes cluster is valuable when you want to test multiple microservices together or test with services that the application requires.

Ensure that your kubectl command is configured with cluster details and run the following command to deploy the application:

appsody deploy

This command builds a new Docker image that is optimized for production deployment and deploys the image to your local Kubernetes cluster. After some time you see a message similar to the following example:

Deployed project running at http://localhost:30262

Run the following command to check the status of the application pods:

kubectl get pods

In the following example output, you can see that a simple-nodejs-express pod is running:

NAME                                    READY   STATUS    RESTARTS   AGE
appsody-operator-6bbddbd455-nfhnm        1/1     Running   0          26d
simple-nodejs-express-775b655768-lqn6q   1/1     Running   0          3m10s

After the simple-nodejs-express pod starts, go to the URL that was returned when you ran the appsody deploy command, and you see the splash screen. To see the response from your application, point your browser to the <URL_STRING>/example URL, where <URL_STRING> is the URL that was returned. For example, http://localhost:30262 was returned in the previous example. Go to the http://localhost:30262/example URL to see the deployed application response.

Use the following command to stop the deployed application:

appsody deploy delete

After you run this command and the deployment is deleted, you see the following message:

Deployment deleted

Testing with serverless

You can choose to test an application that is deployed with serverless to take advantage of Scale to Zero. Not all applications can be written to effectively take advantage of Scale to Zero. The Kabanero operator-based installation configures serverless on the Kubernetes cluster. Because of the resources that are required to run serverless and its dependencies, testing locally can be difficult. Publish to Kubernetes by using pipelines that are described later in the guide. Your operations team can configure the pipelines so that serverless is enabled for deployment.

Publishing to Kubernetes by using pipelines

After you develop and test your application in your local environment, it’s time to publish it to your enterprise’s pipeline. From your enterprise’s pipeline, you can deploy the application to the appropriate Kubernetes cluster for staging or production. Complete this process in Git.

When Kabanero is installed, deploying applications to a Kubernetes cluster always occurs through the DevOps pipeline that is triggered in Git. Using DevOps pipelines to deploy applications ensures that developers can focus on application code, not on containers or Kubernetes infrastructure. From an enterprise perspective, this deployment process ensures that both the container image build and the deployment to Kubernetes or serverless happen in a secure and consistent way that meets company standards.

To deliver your application to the pipeline, push the project to the pre-configured Git repository that has a configured webhook. This configured webhook triggers the enterprise build and deploy pipeline.

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