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Metaparticle for Javascript

Metaparticle/Package for Javascript Tutorial

This is an in-depth tutorial for using Metaparticle/Package for Javascript

For a quick summary, please see the about metaparticle.

Initial Setup

Check the tools

The docker command line tool needs to be installed and working. Try: docker ps to verify this. Go to the install page if you need to install Docker.

The mp-compiler command line tool needs to be installed and working. Try mp-compiler --help to verify this. Go to the releases page if you need to install the Metaparticle compiler.

Get the code

$ git clone https://github.com/metaparticle-io/package
$ cd package/tutorials/javascript/
# [optional, substitute your favorite editor here...]
$ code .

Initial Program

Inside of the tutorials/javascript directory, you will find a simple node project.

You can build this project with npm run.

The initial code is a very simple “Hello World”

const http = require('http');
const os = require('os');
const port = 8080;

const server = http.createServer((request, response) => {
	console.log(request.url);
	response.end(`Hello World: hostname: ${os.hostname()}\n`);
});

server.listen(port, (err) => {
	if (err) {
		return console.log('server startup error: ', err);
	}
	console.log(`server up on ${port}`);
);

You can run this with npm start.

Step One: Containerize the Application

To build a container from our simple application we need to add a dependency to our build file, and then update the code.

Run:

npm install -s @metaparticle/package

Then update the code to read as follows:

const http = require('http');
const os = require('os');
const mp = require('@metaparticle/package');

const port = 8080;

const server = http.createServer((request, response) => {
	console.log(request.url);
	response.end(`Hello World: hostname: ${os.hostname()}\n`);
});

mp.containerize(
	{
		repository: 'docker.io/docker-user-goes-here',
	},
	() => {
		server.listen(port, (err) => {
			if (err) {
				return console.log('server startup error: ', err);
			}
			console.log(`server up on ${port}`);
		});
	}
);

You will notice that we added a mp.containizerize(...) function. This function takes two arguments, an object that describes how to package the application. You will need to replace your-docker-user-goes-here with an actual Docker repository path.

The containerize also takes a function to execute inside the container, in this case the web server.

Once you have this, you can run the program with:

npm start

This code will start your web server again. But this time, it is running inside a container. You can see this by running:

docker ps

Step Two: Exposing the ports

If you try to access the web server on http://localhost:8080 you will see that you can not actually access the server. Despite it running, the service is not exposed. To do this, you need to add a public: true and supply the ports to expose.

The code snippet to add is:

...
mp.containerize(
	{
                ...
		ports: [8080],
        	public: true
	},...

This tells the runtime the port(s) to expose. The complete code looks like:

const http = require('http');
const os = require('os');
const mp = require('@metaparticle/package');

const port = 8080;

const server = http.createServer((request, response) => {
	console.log(request.url);
	response.end(`Hello World: hostname: ${os.hostname()}\n`);
});

mp.containerize(
	{
		ports: [8080],
		repository: 'docker.io/docker-user-goes-here',
		publish: true,
		public: true
	},
	() => {
		server.listen(port, (err) => {
			if (err) {
				return console.log('server startup error: ', err);
			}
			console.log(`server up on ${port}`);
		});
	}
);

Now if you run this with npm run your webserver will be successfully exposed on port 8080.

Replicating and exposing on the web.

As a final step, consider the task of exposing a replicated service on the internet. To do this, we’re going to expand our usage of the options object. First we will add a replicas field, which will specify the number of replicas. Second we will set our execution environment to metaparticle which will launch the service into the currently configured Kubernetes environment.

Here’s what the snippet looks like:

mp.containerize(
        {
        	ports: [8080],
        	replicas: 4,
                runner: 'metaparticle',
                repository: 'docker.io/docker-user-goes-here',
                publish: true,
                public: true
        },
        ...);
...

And the complete code looks like:

const http = require('http');
const os = require('os');
const mp = require('@metaparticle/package');

const port = 8080;

const server = http.createServer((request, response) => {
	console.log(request.url);
	response.end(`Hello World: hostname: ${os.hostname()}\n`);
});

mp.containerize(
	{
        	ports: [8080],
        	replicas: 4,
		runner: 'metaparticle',
		repository: 'docker.io/docker-user-goes-here',
		publish: true,
		public: true
	},
	() => {
		server.listen(port, (err) => {
			if (err) {
				return console.log('server startup error: ', err);
			}
			console.log(`server up on ${port}`);
		});
	}
);
...

After you compile and run this, you can see that there are four replicas running behind a Kubernetes Service Load balancer:

$ kubectl get pods
...
$ kubectl get services
...

Still looking for more? Continue on to the more advanced sharding tutorial