使用Docker Compose管理Docker容器

上一篇创建了一个PHP的运行环境，现在需要一个MySQL服务，直接运行：

root@thinkpad:~# docker run --name rocket-mysql -v /home/rocketfish/mysql/data:/var/lib/mysql -e MYSQL_ROOT_PASSWORD=root -d mysql:5.7

这时候，要运行一个Web服务我们需要运行两次的docker run才可以，如果还有更多的Web容器或其他的服务容器呢？
Docker官方提倡一个容器仅提供一个服务，多个服务/容器可以使用docker-compose来管理。
docker-compose本身是一个Python写的工具，可以直接通过pip安装：

root@thinkpad:~# sudo pip install --upgrade pip

 如果你本地并没有Python环境，也可以采用docker-compose的docker镜像来运行：

root@thinkpad:/home/compose-web# curl -L https://github.com/docker/compose/releases/download/1.8.0/run.sh > /usr/local/bin/docker-compose
root@thinkpad:/home/compose-web# docker-compose --version
#开始下载镜像，建议用第一种

 查看帮助

root@thinkpad:~# docker-compose -h
Define and run multi-container applications with Docker.
 
Usage:
  docker-compose [-f <arg>...] [options] [COMMAND] [ARGS...]
  docker-compose -h|--help
 
Options:
  -f, --file FILE             Specify an alternate compose file (default: docker-compose.yml)
  -p, --project-name NAME     Specify an alternate project name (default: directory name)
  --verbose                   Show more output
  -v, --version               Print version and exit
  -H, --host HOST             Daemon socket to connect to
 
  --tls                       Use TLS; implied by --tlsverify
  --tlscacert CA_PATH         Trust certs signed only by this CA
  --tlscert CLIENT_CERT_PATH  Path to TLS certificate file
  --tlskey TLS_KEY_PATH       Path to TLS key file
  --tlsverify                 Use TLS and verify the remote
  --skip-hostname-check       Don't check the daemon's hostname against the name specified
                              in the client certificate (for example if your docker host
                              is an IP address)
 
Commands:
  build              Build or rebuild services
  bundle             Generate a Docker bundle from the Compose file
  config             Validate and view the compose file
  create             Create services
  down               Stop and remove containers, networks, images, and volumes
  events             Receive real time events from containers
  exec               Execute a command in a running container
  help               Get help on a command
  kill               Kill containers
  logs               View output from containers
  pause              Pause services
  port               Print the public port for a port binding
  ps                 List containers
  pull               Pulls service images
  push               Push service images
  restart            Restart services
  rm                 Remove stopped containers
  run                Run a one-off command
  scale              Set number of containers for a service
  start              Start services
  stop               Stop services
  unpause            Unpause services
  up                 Create and start containers
  version            Show the Docker-Compose version information

mkdir docker
cd docker
mkdir web
mkdir db
vim docker-compose.yml

 内容如下：

version: '2'
services:
  db:
    image: mysql:5.7
    ports:
    - "3306:3306"
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: web
      MYSQL_USER: root
      MYSQL_PASSWORD: rootweb
    volumes:
    - ./db/data:/var/lib/mysql
  web:
    depends_on:
      - db
    image: nginx-php-fpm:phalcon
    ports:
    - "80:80"
    restart: always
    environment:
      WEB_DB_HOST: db:3306
      WEB_DB_PASSWORD: root
    volumes:
    - ./web/html:/var/www/html/
    links:
    - db

这里的volumes定义了要映射进容器的文件或文件夹或者数据容器，可以参考这里。注意，多个容器共享同一个目录，会出现写冲突，比如MySQL，多个实例，数据目录需要分开。所以设计好你的程序，哪一部分是需要只读的（可以共享)，哪一部分是需要写的；写的部分是否可以放到各自临时目录，或者其他公共服务里面。
运行并查看

root@thinkpad:/home/compose-web# docker-compose up -d
Creating network "composeweb_default" with the default driver
Creating composeweb_db_1
Creating composeweb_web_1
root@thinkpad:/home/compose-web# docker-compose ps
      Name                   Command             State              Ports            
------------------------------------------------------------------------------------
composeweb_db_1    docker-entrypoint.sh mysqld   Up      0.0.0.0:3306->3306/tcp     
composeweb_web_1   /start.sh                     Up      443/tcp, 0.0.0.0:80->80/tcp
#也可以使用原来的命令
root@thinkpad:/home/compose-web# docker ps
CONTAINER ID        IMAGE                   COMMAND                  CREATED             STATUS              PORTS                         NAMES
efbdaf257748        nginx-php-fpm:phalcon   "/start.sh"              13 seconds ago      Up 11 seconds       0.0.0.0:80->80/tcp, 443/tcp   composeweb_web_1
a6935d20911e        mysql:5.7               "docker-entrypoint.sh"   14 seconds ago      Up 13 seconds       0.0.0.0:3306->3306/tcp        composeweb_db_1

docker-compose仅仅提供了对多个docker服务的管理，仍然可以在这些容器上运行原来的docker命令。检查下web容器的IP： 

root@thinkpad:/home/compose-web# docker inspect composeweb_web_1 | grep IPAddress
            "SecondaryIPAddresses": null,
            "IPAddress": "",
                    "IPAddress": "172.18.0.3",

root@thinkpad:/home/compose-web# docker-compose stop db
Stopping composeweb_db_1 ... done
root@thinkpad:/home/compose-web# docker-compose stop web
Stopping composeweb_web_1 ... done

root@thinkpad:/home/compose-web# docker-compose up -d
Starting composeweb_db_1
Starting composeweb_web_1

docker-compose的配置还有很多其他的参数，可以参考这里。比如刚才我们通过docker inspect来查找容器IP，也可以配置成静态IP：

version: '2'
 
services:
  app:
    image: nginx-php-fpm:phalcon
    networks:
      app_net:
        ipv4_address: 172.18.0.10
        ipv6_address: 2001:3984:3989::10
 
networks:
  app_net:
    driver: bridge
    driver_opts:
      com.docker.network.enable_ipv6: "true"
    ipam:
      driver: default
      config:
      - subnet: 172.18.0.0/24
        gateway: 172.18.0.1
      - subnet: 2001:3984:3989::/64
        gateway: 2001:3984:3989::1

刚才我们的配置文件里面直接指定了镜像，也可以指定Dockerfile镜像构建，假如Dockerfile在web目录下面:

build:
  context: ./web

build:
  context: .
  dockerfile: Dockerfile-alternate

command: [/bin/bash]

 这里的入口程序，如果不能持续运行的话，运行完成后，docker就会退出。所以如果你需要可以后台运行的docker容器，那么入口程序，就必须保持一个程序在前台运行，不退出，比如运行crontab的镜像，入口程序可以是：

cron && bash

 cron这个程序是在后台运行的，如果不配合前台程序bash，容器执行玩cron就会退出了。其他运行crontab的容器，大都是强制一个程序在前台不退出，比如这个：

cron && tail -f /var/log/cron.log

 Docker compose还可以跟Docker Swarm结合。

参考链接：
Install Docker Compose
Quickstart: Docker Compose and WordPress
YAML 模板文件
Introduction to Docker Compose Tool for Multi-Container Applications
Dockerfile基本结构
How to Get Environment Variables Passed Through docker-compose to the Containers

博客原文：使用Docker Compose管理Docker容器