有一个node应用，部署在多个容器中，需要用到redis存储，同时我想要将node应用和redis独立开来，然后用Nginx在最前端负载均衡这些应用。

1 Nginx container
可以得到如下架构图：

有两种方法可以构建该连接，一：从空白的操作镜像（如：Ubuntu、Debian等）开始构建；二：从一个预先构建好的镜像；这里选择使用一个Redis镜像、一个Nginx镜像和一个基于Ubuntu的node镜像

Redis container
从官方Docker Hub中下载Redis镜像，构建一个Redis容器，端口默认6379

docker run -d --name redis -p 6379:6379 redis
***Dockerfile ***：
# Set the base image to Ubuntu
FROM        ubuntu
# File Author / Maintainer
MAINTAINER InfiniteRain
# Update the repository and install Redis Server
RUN         apt-get update && apt-get install -y redis-server
# Expose Redis port 6379
EXPOSE      6379
# Run Redis Server
ENTRYPOINT  ["/usr/bin/redis-server"]
Node container

从Node镜像中生成一个node容器，同时在应用中指定6379端口为redis侦听的端口。

index.js
var express = require('express'),
    http = require('http'),
    redis = require('redis');
var app = express();
console.log(process.env.REDIS_PORT_6379_TCP_ADDR + ':' + process.env.REDIS_PORT_6379_TCP_PORT);
var client = redis.createClient('6379', 'redis');
app.get('/', function(req, res, next) {
  client.incr('counter', function(err, counter) {
    if(err) return next(err);
    res.send('This page has been viewed ' + counter + ' times!, HOSTNAME:' + process.env.HOSTNAME);
http.createServer(app).listen(process.env.PORT || 8080, function() {
  console.log('Listening on port ' + (process.env.PORT || 8080));
***Dockerfile ***：
# Set the base image to Ubuntu
FROM    ubuntu
# File Author / Maintainer
MAINTAINER InfiniteRain
# Install Node.js and other dependencies
RUN apt-get update && \
    apt-get -y install curl && \
    curl -sL https://deb.nodesource.com/setup_8.x | sudo bash - && \
    apt-get -y install python build-essential nodejs
# Install nodemon
RUN npm install -g nodemon
# Provides cached layer for node_modules
ADD package.json /tmp/package.json
RUN cd /tmp && npm install
RUN mkdir -p /src && cp -a /tmp/node_modules /src/
# Define working directory
WORKDIR /src
ADD . /src
# Expose port
EXPOSE  8080
# Run app using nodemon
CMD ["nodemon", "/src/index.js"]
使用Dockerfile构建一个镜像
docker build -t infinite/node .
创建一个Node容器，指定8080端口，并且连接redis容器
docker run -d --name node -p 8080 --link redis:redis infinite/node
依照上述方法创建三个相同的容器 node1、node2、node3
Nginx container

同样从Docker Hub中拉取镜像，并生成一个名为infinite/nginx的容器

Nginx中关于负载均衡的配置

nginx.conf
worker_processes 4;
events { worker_connections 1024; }
http {
        upstream node-app {
              least_conn;
              server node1:8080 weight=10 max_fails=3 fail_timeout=30s;
              server node2:8080 weight=10 max_fails=3 fail_timeout=30s;
              server node3:8080 weight=10 max_fails=3 fail_timeout=30s;
        server {
              listen 80;
              location / {
                proxy_pass http://node-app;
                proxy_http_version 1.1;
                proxy_set_header Upgrade $http_upgrade;
                proxy_set_header Connection 'upgrade';
                proxy_set_header Host $host;
                proxy_cache_bypass $http_upgrade;
Dockerfile
# Set nginx base image
FROM nginx
# File Author / Maintainer
MAINTAINER InfiniteRain
# Copy custom configuration file from the current directory
COPY nginx.conf /etc/nginx/nginx.conf
docker build -t infinite/nginx .
docker run -d --name nginx -p 80:80 --link node:node infinite/nginx
使用Docker Compose组合应用程序

docker-compose.yml
nginx:
    build: ./nginx
    links:
        - node1:node1
        - node2:node2
        - node3:node3
    ports:
        - "80:80"
node1:
    build: ./node
    links:
        - redis
    ports:
        - "8080"
node2:
    build: ./node
    links:
        - redis
    ports:
        - "8080"
node3:
    build: ./node
    links:
        - redis
    ports:
        - "8080"
redis:
    image: redis
    ports:
        - "6379"
上述YAML文件为各个容器定义了名称，指定了Dockerfile文件，同时还包括了容器之间的连接关系。只需要一个命令docker-compose up就可以建好这五个容器了。最后文件结构如图：