Dockerizing a Node.js web app

The goal of this example is to show you how to get a Node.js application into a Docker container. The guide is intended for development, and not for a production deployment. The guide also assumes you have a working Docker installation and a basic understanding of how a Node.js application is structured.

示例展示了如何在Docker容器中运行一个Node.js程序,在继续之前，我们假定你已经有知道如何安装Docker并且理解Node.js程序是如何组织的。

In the first part of this guide we will create a simple web application in Node.js, then we will build a Docker image for that application, and lastly we will run the image as container.

在文档的第一部分，我们会用Node.js创建一个简单的web应用程序，之后为这个应用生成一个Docker镜像，最后将这个镜像作为容器来运行。

Docker allows you to package an application with all of its dependencies into a standardized unit, called a container, for software development. A container is a stripped-to-basics version of a Linux operating system. An image is software you load into a container.

在软件开发中Docker允许我们将一个程序以及它的所有依赖打包进一个标准化单元——容器，容器是一个只保留了基础功能的Linux发行版，镜像是运行在容器中的软件。

Create the Node.js app

First, create a new directory where all the files would live. In this directory create a package.json file that describes your app and its dependencies:

首先，创建一个存放所有项目文件的文件夹，在这个文件夹中创建一个描述它依赖的 package.json 文件：

{    "name": "docker_web_app",    "version": "1.0.0",    "description": "Node.js on Docker",    "author": "First Last <first.last@example.com>",    "main": "server.js",    "scripts": {      "start": "node server.js"    },    "dependencies": {      "express": "^4.13.3"    }  }

Then, create a server.js file that defines a web app using the Express.js framework:

然后创建一个基于 Express.js 框架的web程序的描述文件：

'use strict';    const express = require('express');    // Constants  const PORT = 8080;    // App  const app = express();    app.get('/', function (req, res) {      res.send('Hello world\n');  });    app.listen(PORT);    console.log('Running on http://localhost:' + PORT);  

In the next steps, we'll look at how you can run this app inside a Docker container using the official Docker image. First, you'll need to build a Docker image of your app.

在下一部中我们会看到在使用官方Docker镜像的容器中运行这个程序，当然，首先我们需要生成一个这个应用的Docker镜像.

Creating a Dockerfile

Create an empty file called Dockerfile :

创建名为 Dockerfile 的空文件:

touch Dockerfile  

Open the Dockerfile in your favorite text editor

在你喜欢的编辑器中打开 Dockerfile

The first thing we need to do is define from what image we want to build from. Here we will use the latest LTS (long term support) version argon of node available from the Docker Hub :

我们需要做的第一件事是定义我们从哪个镜像来构建，在这里我们使用 node 的长期支持版本 argon 来构建，它可以从 Docker Hub 处来获得：

FROM node:argon  

Next we create a directory to hold the application code inside the image, this will be the working directory for your application:

# Create app directory  RUN mkdir -p /usr/src/app    WORKDIR /usr/src/app  

This image comes with Node.js and NPM already installed so the next thing we need to do is to install your app dependencies using the npm binary:

# Install app dependencies  COPY package.json /usr/src/app/    RUN npm install  

# Bundle app source  COPY . /usr/src/app  

Your app binds to port 8080 so you'll use the EXPOSE instruction to have it mapped by the docker daemon:

EXPOSE 8080  

Last but not least, define the command to run your app using CMD which defines your runtime. Here we will use the basic npm start which will run node server.js to start your server:

CMD [ "npm", "start" ]  

Your Dockerfile should now look like this:

FROM node:argon    # Create app directory  RUN mkdir -p /usr/src/app    WORKDIR /usr/src/app    # Install app dependencies  COPY package.json /usr/src/app/    RUN npm install    # Bundle app source  COPY . /usr/src/app    EXPOSE 8080    CMD [ "npm", "start" ]  

Building your image

Go to the directory that has your Dockerfile and run the following command to build the Docker image. The -t flag lets you tag your image so it's easier to find later using the docker images command:

$ docker build -t <your username>/node-web-app .

Your image will now be listed by Docker:

$ docker images    # Example  REPOSITORY                      TAG        ID              CREATED    node                            argon      539c0211cd76    3 weeks ago    <your username>/node-web-app    latest     d64d3505b0d2    1 minute ago  

Run the image

Running your image with -d runs the container in detached mode, leaving the container running in the background. The -p flag redirects a public port to a private port inside the container. Run the image you previously built:

$ docker run -p 49160:8080 -d <your username>/node-web-app

Print the output of your app:

# Get container ID  $ docker ps    # Print app output  $ docker logs <container id>    # Example  Running on http://localhost:8080  

If you need to go inside the container you can use the exec command:

# Enter the container  $ docker exec -it <container id> /bin/bash

Test

To test your app, get the port of your app that Docker mapped:

$ docker ps    # Example  ID            IMAGE                                COMMAND    ...   PORTS    ecce33b30ebf  <your username>/node-web-app:latest  npm start  ...   49160->8080  

In the example above, Docker mapped the 8080 port inside of the container to the port 49160 on your machine.

Now you can call your app using curl (install if needed via: sudo apt-get install curl ):

$ curl -i localhost:49160    HTTP/1.1 200 OK    X-Powered-By: Express    Content-Type: text/html; charset=utf-8    Content-Length: 12    Date: Sun, 02 Jun 2013 03:53:22 GMT    Connection: keep-alive    Hello world  

We hope this tutorial helped you get up and running a simple Node.js application on Docker.

You can find more information about Docker and Node.js on Docker in the following places:

• Official Node.js Docker Image
• Official Docker documentation
• Docker Tag on StackOverflow
• Docker Subreddit
• Build your own images

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