How to use Docker's Compose to implement nginx load balancing

Using docker network management and container ip settings as basic knowledge to implement nginx load balancing

View all docker networks

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

Specify the container ip address

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

Use docker-compose to start the container

docker-compose up -d

Check whether the container is started and confirm whether the network nginx-lsb is created

// 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

View the details of the network nginx-lsb

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": ""
      }
    },
...
*/

Use env_file environment file:

It can be simply understood as: define variables in docker-compose.yml, and reference variables in external .env files

Official document address:

// 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

Restart the composetest project, and check the network details to confirm whether the container ip is set successfully

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

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

Add an nginx server as a load balancing server in the composetest project

// 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

Modify the nginx.conf configuration file, configure load balancing

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;
  }
}

Restart nginx-lsb, load the configuration file

docker-composer restart nginx-lsb

Visit http://server ip address:8000, test server load balancing!

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