使用Docker Compose 实现nginx负载均衡

以docker的网络管理，容器的IP设置为基础知识实现Nginx负载均衡

查看所有docker网络

docker network ls

/*
NETWORK ID     NAME         DRIVER       SCOPE
b832b168ca9a    bridge        bridge       local
373be82d3a6a    composetest_default  bridge       local
a360425082c4    host         host        local
154f600f0e90    none         null        local

*/

// composetest_default 是上一篇介绍Compose时，docker-compose.yml文件所在的目录名，
// 所以，用docker-compose创建的容器会默认创建一个以目录名为网络名的网络，并且是dridge（桥接）类型

指定容器IP地址

官网文档地址：https://docs.docker.com/compose/compose-file/#ipv4_address-IPv6_address

继续编写上一篇《12.使用Docker Compose容器编排工具》文章中的docker-compose.yml

version: "3"
services:
  web1:
    container_name: web1
    image: "centos:httpd"
    ports:
      - "8080:80"
    privileged: true
    volumes:
      - "/app/www/web1/:/var/www/html/"
    command: ['/usr/sbin/init']
    networks:
      nginx-lsb:
        ipv4_address: 192.169.0.3
  web2:
    container_name: web2
    image: "centos:httpd"
    ports:
      - "8081:80"
    privileged: true
    volumes:
      - "/app/www/web2/:/var/www/html/"
    command: ['/usr/sbin/init']
    networks:
      nginx-lsb:
        ipv4_address: 192.169.0.2
networks:
  nginx-lsb:
    driver: bridge
    ipam:
      config:
        - subnet: 192.169.0.0/16

使用docker-compose启动容器

docker-compose up -d

查看容器是否启动，并确认是否创建了网络 nginx-lsb

// 可以查看当前docker-compose.yml配置的容器组里的容器状态
docker-compose ps

docker network ls

/*
NETWORK ID     NAME          DRIVER       SCOPE
b832b168ca9a    bridge         bridge       local
373be82d3a6a    composetest_default   bridge       local
de6f5b8df1c8    composetest_nginx-lsb  bridge       local
a360425082c4    host          host        local
154f600f0e90    none          null        local
*/

// 创建了nginx-lsb网络，命名是容器组项目的 文件名开头_网络名

查看网络 nginx-lsb的详情

docker network inspect composetest_nginx-lsb

// 详情里面可以看到使用这个网络的每个容器的ip

如：

/*
...
 "Containers": {
      "039aa860ef04f20a7566fdc943fb4398a61d2ad6dd3e373b17c86ac778af89e3": {
        "Name": "web2",
        "EndpointID": "1bc206661179e65999015f132c2889d3d4365b8d42b8a89cf9c260016fedd5ee",
        "MacAddress": "02:42:c0:a9:00:02",
        "IPv4Address": "192.169.0.2/16",
        "IPv6Address": ""
      },
      "437ad7a07da8e46c0abaf845c4b08425338009fbe972bde69478cf47c75c315b": {
        "Name": "web1",
        "EndpointID": "5a36e602a5364ee9ad06e9816d09e3966d56ebf06b9394ebc25b8bcee9546607",
        "MacAddress": "02:42:c0:a9:00:03",
        "IPv4Address": "192.169.0.3/16",
        "IPv6Address": ""
      }
    },
...
*/

使用 env_file环境文件：

简单可以理解为：在docker-compose.yml中定义变量，引用在外部.env文件中进行变量定义

官方文档地址：https://docs.docker.com/compose/compose-file/#env_file

// 还是在composetest目录中定义个 .env文件，用来存放变量
web1_addr=192.169.0.2
web2_addr=192.169.0.3

// 修改docker-compose.yml文件，加入变量定义
version: "3"
services:
  web1:
    container_name: web1
    image: "centos:httpd"
    ports:
      - "8080:80"
    privileged: true
    volumes:
      - "/app/www/web1/:/var/www/html/"
    command: ['/usr/sbin/init']
    networks:
      nginx-lsb:
        ipv4_address: ${web1_addr}
  web2:
    container_name: web2
    image: "centos:httpd"
    ports:
      - "8081:80"
    privileged: true
    volumes:
      - "/app/www/web2/:/var/www/html/"
    command: ['/usr/sbin/init']
    networks:
      nginx-lsb:
        ipv4_address: ${web2_addr}
networks:
  nginx-lsb:
    driver: bridge
    ipam:
      config:
        - subnet: 192.169.0.0/16

重新启动composetest项目，并查看网络详情，确认容器ip是否设置成功

// 重新启动composetest项目
docker-compose up -d

// 查看网络详情
docker network inspect composetest_nginx-lsb

在composetest项目中添加一台nginx服务器作为负载均衡服务器

// 在.env文件里添加一个变量 nginx_lsb
web1_addr=192.169.0.2
web2_addr=192.169.0.3
nginx_lsb=192.169.0.100

// 修改docker-compose.yml文件，加入变量定义
version: "3"
services:
  nginx-lsb:
    container_name: nginx-lsb
    image: "centos:nginx"
    ports: 
      - "8000:80"
    privileged: true
    volumes:
      - "/app/nginx/nginx.conf:/etc/nginx/nginx.conf"
    networks:
      nginx-lsb:
        ipv4_address: ${nginx_lsb}
  web1:
    container_name: web1
    image: "centos:httpd"
    ports:
      - "8080:80"
    privileged: true
    volumes:
      - "/app/www/web1/:/var/www/html/"
    command: ['/usr/sbin/init']
    networks:
      nginx-lsb:
        ipv4_address: ${web1_addr}
  web2:
    container_name: web2
    image: "centos:httpd"
    ports:
      - "8081:80"
    privileged: true
    volumes:
      - "/app/www/web2/:/var/www/html/"
    command: ['/usr/sbin/init']
    networks:
      nginx-lsb:
        ipv4_address: ${web2_addr}
networks:
  nginx-lsb:
    driver: bridge
    ipam:
      config:
        - subnet: 192.169.0.0/16

// 重新启动composetest项目
docker-compose up -d

修改nginx.conf配置文件，配置负载均衡

upstream mydocker {
  server 192.169.0.2;
  server 192.169.0.3;
}

server {
  listen 80；
  server_name mydocker;
  location / {
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_buffering off;
    proxy_pass http://mydocker;
  }
}

重新启动nginx-lsb，加载配置文件

docker-composer restart nginx-lsb

访问 http://服务器IP地址:8000，测试服务器负载均衡！