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In this final stage, we'll take everything we've learned so far and Dockerize a simple Node.js web app.
This Node.js web app simply listens for connections on port 80, and responds with the message "Hello from Node.js!".
server.js
'use strict';
const express = require('express');
// Constants
const PORT = 80;
const HOST = '0.0.0.0';
// App
const app = express();
app.get('/', (req, res) => {
res.send('Hello from Node.js!\n');
});
app.listen(PORT, HOST);
console.log(`Running on http://${HOST}:${PORT}`);
Like most Node apps, this app also includes a file named package.json that defines how it's built. The "start" line is particularly important; it contains the command that will run the server.
package.json
{
"name": "docker_web_app",
"version": "1.0.0",
"description": "Node.js on Docker",
"author": "Jared Smith <jared@jaredthecoder.com>",
"main": "server.js",
"scripts": {
"start": "node server.js"
},
"dependencies": {
"express": "^4.13.3"
}
}
Now that we have our server code, it's time to build the Dockerfile to deploy it!
# Build off this base image
FROM node:7
# Set up app directory
WORKDIR /usr/src/app
# Install app dependencies
COPY package.json /usr/src/app/
RUN npm install
# Bundle app source
COPY . /usr/src/app
# Expose the server to the host machine
EXPOSE 8080
# Run this command on startup
ENTRYPOINT ["npm", "start"]
New Terms
- Node.js: A JavaScript runtime for non-browser environments.
- package.json: A file that defines a JavaScript packages settings (i.e. how to build it, how to start it, metadata, etc.)
- Express: A JavaScript/Node.js web server framework, like Flask or Django for Python, or Sinatra or Ruby on Rails for Ruby.
- NPM: Node.js Package Manager, the package manager for installing JavaScript/Node.js packages into your development or production environment.
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In this final stage, we'll take
everything we've learned so far and
0:00
dockerize this simple Node.js web app.
0:04
See the teacher's notes if you'd like to
retrieve a copy of the app for yourself.
0:06
Node.js is a run-time that allows
you to run JavaScript on a server.
0:10
This app simply listens for
connections on port 80, and
0:15
responds with the message,
Hello from Node.js.
0:18
It's quite short,
0:21
because it relies on the express
framework to handle browser requests.
0:23
So to make this work
in a Docker container,
0:27
we're going to need both Node.js and
the express library installed.
0:29
Like most node apps, this app also
includes a file named package.json,
0:33
that defines how it's built.
0:38
The start line is particularly important.
0:40
It contains the command
that will run the server.
0:42
Now that we have our server code,
0:46
it's time to build the Docker
file to deploy it.
0:47
As usual, in the same directory
as the app code, create a file,
0:50
named, Docker file, with a capital D,
and no file name extension.
0:54
The first thing we'll want to do
is ensure our new docker image is
0:58
using an appropriate base image,
we'll do that using the from instruction.
1:02
From takes the name and
tag of an image to use,
1:07
we'll use the Node image from docker hub.
1:10
The maintainers of the node docker images
chose to tag their images with the node
1:13
version number so we'll write a colon and
then a tag with the version we want, 7.
1:18
Now we want to create a directory
inside image that will house our app.
1:23
The WORKDIR instruction will create
a directory, and also ensure that all
1:27
remaining instructions in this Docker
file, operate within that directory.
1:32
We'll give it a path of /usr/src/app.
1:37
Next we need to install
our app's dependencies.
1:41
Since we're using the node base image,
Node.js and
1:44
its package manager,
NPM will already be installed.
1:49
We can just use NPM to install the express
library and any other dependencies for us,
1:54
but NPM needs our package.json file so
that it knows what packages to install.
2:01
So we'll use the copy instruction
to copy the package.json file from
2:06
the directory on our host to the image.
2:11
Because we set the working directory
to user/src/app earlier in the file,
2:17
all we have to do is provide a target
file name of package.json, and
2:22
it'll copy the file straight
into the app directory.
2:27
With the package.json file copied over,
we'll be able to run NPM.
2:30
We can execute commands while building
an image with the RUN instruction,
2:35
and we'll run a command of npm install.
2:40
That'll read the package.json file,
see that our app has a dependency
2:42
on the express web framework,
and install it for us.
2:47
In addition to the package.js
file we're of course going to
2:51
need the file containing the app itself.
2:55
We can use another copy instruction to
copy that over to the working directory,
2:58
COPY server.js, to a destination file of,
3:03
server.js, which of course
that will take place within,
3:07
that'll be copied to the user
source app directory by default.
3:11
Our server is going to
be running on port 80.
3:16
So the browsers can connect,
3:18
we're going to need to expose
that port on the container.
3:20
We do that with the EXPOSE instruction,
and we'll expose port 80,
3:22
and lastly we need to run the server
when the container starts up.
3:28
NPM can use the start instruction in our
package.json file to launch the server,
3:33
but we need to launch NPM.
3:39
So we'll use the ENTRYPOINT instruction,
and that'll set up a command to run.
3:41
We'll have it run the npm command.
3:49
And we'll pass an argument
of start to npm.
3:54
We'll save that and
that should be all the setup we need.
3:57
In the next video, we'll build and
run the image, and try it out.
4:01
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