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一、wordpress部署

这里先以wordpress的部署为例引出Docker Compose,wordpress的部署需要wordpress和mysql的镜像:

(一)准备环境

1、拉取wordpress镜像

[root@docker-node1 /]# docker pull wordpress

2、拉取mysql镜像

[root@docker-node1 /]# docker pull mysql

3、镜像列表

[root@docker-node1 /]# docker image ls
REPOSITORY            TAG         IMAGE ID      CREATED       SIZE
wordpress            latest       0947f14b932b    25 hours ago    540MB
mysql              latest       791b6e40940c    43 hours ago    465MB

(二)运行镜像

1、运行mysql镜像

root@docker-node1 /]# docker run -d --name mysql -v mysql-data:/var/lib/mysql -e MYSQL_ROOT_PASSWORD=root -e MYSQL_DATABASE=wordpress mysql
b6e7a57a5fcec79f436d3f65240adf833340b4a9640e3b4f9282870078fb8e57

上述命令中 -v指定存储卷,MYSQL_ROOT_PASSWORD设置数据库密码,MYSQL_DATABASE指定创建数据库的名称,详情参考:https://hub.docker.com/_/mysql

查看启动的容器:

[root@docker-node1 /]# docker ps
CONTAINER ID    IMAGE        COMMAND         CREATED       STATUS       PORTS         NAMES
b6e7a57a5fce    mysql        "docker-entrypoint.s…"  6 minutes ago    Up 6 minutes    3306/tcp, 33060/tcp  mysql

2、启动wordpress镜像

[root@docker-node1 /]# docker run --name wordpress -e WORDPRESS_DB_HOST=mysql:3306 --link mysql -p 8080:80 -d wordpress
6cf0c0fc2ef332728a3ea2bf2dbee65299441b26751d5c64f0a66b329f2679f6

上述命令中WORDPRESS_DB_HOST是需要连接的数据库,指定的就是刚刚创建的mysql容器,这里没有输入WORDPRESS_DB_USER、WORDPRESS_DB_PASSWORD的密码等环境信息,因为默认的就是mysql容器的用户名、密码,详情查看:https://hub.docker.com/_/wordpress。

然后查看容器信息:

[root@docker-node1 /]# docker ps
CONTAINER ID    IMAGE        COMMAND         CREATED       STATUS       PORTS         NAMES
6cf0c0fc2ef3    wordpress      "docker-entrypoint.s…"  3 minutes ago    Up 3 minutes    0.0.0.0:8080->80/tcp  wordpress
b6e7a57a5fce    mysql        "docker-entrypoint.s…"  20 minutes ago   Up 20 minutes    3306/tcp, 33060/tcp  mysql

目前两个容器都已经起来了,最后可以访问主机的8080端口即可。

二、Docker Compose

从上面的部署上可以看出存在以下问题:

  • 需要单独拉取多个容器,一个个的部署
  • 需要同时管理多个容器(包括启动、停止等动作)

那么有没有一种类似批处理的方式,不需要这么繁琐的过程呢?这就需要Docker Compose了。

(一)Docker Compose简介

1、什么是Docker Compose"htmlcode">

services:
  db:
    image:postgres:9.4
    volumes:
      -"db-data:/var/lib/postgresql/data"
    networks:
      -back-tier

上面这个yml文件中定义了一个service,其实就相当于下面这条命令:

docker run -d --network back-tier -v db-data:/var/lib/postgresql/data postgres:9.4

networks

networks:
  back-tier:
    driver:bridge

上面这个yml文件中定义了一个network,其实就相当于下面这条命令:

docker network create -d bridge back-tier  

volumes

volumes:
  db-data:

上面这个yml文件中定义了一个volume,其实就相当于下面这条命令:

docker volume create db-data

(二)Docker Compose环境准备

Docker Cmpose是一个工具,所以是需要安装的,安装详情参考:https://docs.docker.com/compose/install/。

1、下载可执行文件

sudo curl -L "https://github.com/docker/compose/releases/download/1.25.3/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose

2、设置权限

sudo chmod +x /usr/local/bin/docker-compose

3、查看版本

[root@docker-node1 ~]# docker-compose --version
docker-compose version 1.24.1, build 4667896

4、docker-compose中的常用命令

[root@docker-node1 compose-wordpress]# docker-compose --help
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
 --log-level LEVEL      Set log level (DEBUG, INFO, WARNING, ERROR, CRITICAL)
 --no-ansi          Do not print ANSI control characters
 -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
 --project-directory PATH  Specify an alternate working directory
               (default: the path of the Compose file)
 --compatibility       If set, Compose will attempt to convert keys
               in v3 files to their non-Swarm equivalent

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
 images       List images
 kill        Kill containers
 logs        View output from containers
 pause       Pause services
 port        Print the public port for a port binding
 ps         List containers
 pull        Pull 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
 top        Display the running processes
 unpause      Unpause services
 up         Create and start containers
 version      Show the Docker-Compose version information

docker-compose up

用于启动service创建容器,执行yml文件

docker-compose -d

后台执行容器服务

docker-compose ps

显示正在运行的容器

docker-compose stop

停止正在运行的容器服务

docker-compose down

停止容器服务,并且移除容器(container)、镜像(image)、网络(network)以及存储卷(volume)

docker-compose images

显示通过docker-compose up创建的容器服务的镜像列表

docker-compose exec container(Names) bash

进入某个容器,可以在容器内部进行操作

(三)Docker Compose实战

1、wordpress

编写docker-compose.yml文件

version: '3'  #docker-compose.yml版本

services:  #定义多个容器服务

 wordpress:  #wordpress容器名称
  image: wordpress #镜像来源
  ports:    #端口映射
   - 8080:80
  environment:  #环境变量
   WORDPRESS_DB_HOST: mysql #连接的数据库,就是下面mysql容器的名称
   WORDPRESS_DB_PASSWORD: root #数据库密码
  networks:  #使用的网络,是下面networks中定义的my-bridge
   - my-bridge

 mysql:  #mysql容器名称
  image: mysql #mysql镜像
  command: --default-authentication-plugin=mysql_native_password #解决数据库密码加密问题
  environment: #环境变量
   MYSQL_ROOT_PASSWORD: root
   MYSQL_DATABASE: wordpress
  volumes: #定义存储卷,就是下面volumes中定义的
   - mysql-data:/var/lib/mysql
  networks:
   - my-bridge

volumes:
 mysql-data:

networks:
 my-bridge:
  driver: bridge

启动services中的容器

[root@docker-node1 compose-wordpress]# ls
docker-compose.yml
[root@docker-node1 compose-wordpress]# docker-compose up

通过docker-compose up启动容器,这个命令默认执行的就是当前目录下的docker-compose.yml文件,你也可以将这个命令写完整就是docker-compose -f docker-compose.yml up

2、Flask Web

新建app.py docker-compose.yml Dockerfile三个文件

[root@docker-node1 compose-flask]# ls
app.py docker-compose.yml Dockerfile

编写app.py文件

from flask import Flask
from redis import Redis
import os

app = Flask(__name__)
redis = Redis(host=os.environ.get('REDIS_HOST'),port=6379)

@app.route('/')
def hello():
  return 'Hello World'

if __name__ == "__main__":
  app.run(host="0.0.0.0",port=5000,debug=True)

编写Dockerfile文件

FROM python:2.7
COPY . /app/
WORKDIR /app/
RUN pip install flask redis
EXPOSE 5000
CMD ["python","app.py"]

编写docker-compose.yml文件

version: "3"

services:

 redis:
  image: redis

 web:
  build:
   context: .
   dockerfile: Dockerfile
  ports:
   - 8080:5000
  environment:
   REDIS_HOST: redis

启动容器服务

[root@docker-node1 compose-flask]# docker-compose up

访问服务

Docker Compose多容器部署的实现

(四)水平扩展和负载均衡

1、scale

在上面通过Docker Compose完成了flask的应用部署,目前运行的容器:

[root@docker-node1 compose-flask]# docker-compose ps
    Name            Command        State      Ports     
---------------------------------------------------------------------------------------
compose-flask_redis_1  docker-entrypoint.sh redis ...  Up   6379/tcp       
compose-flask_web_1   python app.py          Up   0.0.0.0:8080->5000/tcp

通过docker-compose --help命令,可以看到有一个scale参数:

[root@docker-node1 compose-flask]# docker-compose --help
  scale       Set number of containers for a service

它的意思就是可以启用多个应用容器:

[root@docker-node1 compose-flask]# docker-compose up --scale web=3 -d

但是显然这样会出错,为什么呢?因为三个容器端口映射都是一样的,必然剩下的两个应用容器会报端口占用的错误。此时需要修改一下docker-compose.yml文件将web应用的端口那一项配置去掉:

version: "3"

services:

 redis:
  image: redis

 web:
  build:
   context: .
   dockerfile: Dockerfile
  ports:     #去掉这一项
   - 8080:5000
  environment:
   REDIS_HOST: redis

这样就可以了。

[root@docker-node1 compose-flask]# docker-compose up --scale web=3 -d
Recreating compose-flask_web_1 ... 
Recreating compose-flask_web_1 ... done
Recreating compose-flask_web_2 ... done
Recreating compose-flask_web_3 ... done

查看容器:

[root@docker-node1 compose-flask]# docker ps
CONTAINER ID    IMAGE        COMMAND         CREATED       STATUS       PORTS    NAMES
d0ae3307eb9e    compose-flask_web  "python app.py"     51 seconds ago   Up 46 seconds    5000/tcp  compose-flask_web_1
67483b8decd3    compose-flask_web  "python app.py"     52 seconds ago   Up 47 seconds    5000/tcp  compose-flask_web_2
741766d49902    compose-flask_web  "python app.py"     52 seconds ago   Up 47 seconds    5000/tcp  compose-flask_web_3
be3800004658    redis        "docker-entrypoint.s…"  5 hours ago     Up 6 minutes    6379/tcp  compose-flask_redis_1

但是显然这样只能在容器内去访问,因为端口没有映射出来,那么这样接下来怎么做呢?

Docker Compose多容器部署的实现

我们接下来可以这样做,用一个HAProxy的容器来接收请求,然后通过端口转发给不同的web服务器,这样就解决以下问题:

  • 外界不能访问,只能容器内访问
  • 负载均衡

2、水平扩展和负载均衡

文件结构

[root@docker-node1 compose-flask]# ls
app.py docker-compose.yml Dockerfile

编写app.py

from flask import Flask
from redis import Redis
import os

app = Flask(__name__)
redis = Redis(host=os.environ.get('REDIS_HOST'),port=6379)

@app.route('/')
def hello():
  return 'Hello World'

if __name__ == "__main__":
  app.run(host="0.0.0.0",port=80,debug=True)

编写Dockerfile文件

FROM python:2.7
COPY . /app/
WORKDIR /app/
RUN pip install flask redis
EXPOSE 80
CMD ["python","app.py"]

编写docker-compose.yml文件

version: "3"

services:

 redis:
  image: redis

 web:
  build:
   context: .
   dockerfile: Dockerfile
  environment:
   REDIS_HOST: redis

 lb:
  image: dockercloud/haproxy
  links:
   - web
  ports:
   - 8080:80
  volumes:
   - /var/run/docker.sock:/var/run/docker.sock

运行

[root@docker-node1 compose-flask]# docker-compose up -d
Creating network "compose-flask_default" with the default driver
Creating compose-flask_web_1  ... done
Creating compose-flask_redis_1 ... done
Creating compose-flask_lb_1  ... done

可以看到启动了三个容器,分别为:

[root@docker-node1 compose-flask]# docker-compose ps
    Name            Command        State         Ports        
---------------------------------------------------------------------------------------------------
compose-flask_lb_1   /sbin/tini -- dockercloud- ...  Up   1936/tcp, 443/tcp,        
                                 0.0.0.0:8080->80/tcp       
compose-flask_redis_1  docker-entrypoint.sh redis ...  Up   6379/tcp             
compose-flask_web_1   python app.py          Up   5000/tcp

我们看到web应用目前只有一个,可以启动多个来处理请求:

[root@docker-node1 compose-flask]# docker-compose up --scale web=5 -d
compose-flask_redis_1 is up-to-date
Starting compose-flask_web_1 ... done
Creating compose-flask_web_2 ... done
Creating compose-flask_web_3 ... done
Creating compose-flask_web_4 ... done
Creating compose-flask_web_5 ... done
compose-flask_lb_1 is up-to-date

可以看到,直接将web应用启动了5个容器,分担从HAProxy的请求。

标签:
Docker,Compose多容器部署,Docker,Compose多容器

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