What is docker container orchestration

In docker, by executing a YAML file, multiple containers defined in the file are started in sequence. This is container orchestration; the tool for implementing container orchestration is "docker-compose". The YAML file defines a series of containers and container runtime properties, and Compose will manage the container based on these configurations.

The operating environment of this tutorial: linux5.9.8 system, docker-1.13.1 version, Dell G3 computer.

Docker container orchestration

What is container orchestration

• By executing a file, multiple containers defined in the file are started in sequence , this is container orchestration
• This file is the yaml file

The tool used to implement container orchestration

• docker-compose

  You can install the Docker Compose tool to implement container orchestration based on YAML files. The YAML file will define a series of containers and container runtime attributes, and Docker Compose will manage the containers based on these configurations.
  

Install docker-compose

• docker-compose in epel source

[root@worker1 ~]# yum install epel-release -y
[root@worker1 ~]# yum install docker-compose -y

Usage of docker-compose command

• Format: docker-compose [options]

• options

  • up: Start the container defined in the yaml file
  • down: Close the container defined in the yaml file
  • -f x.yaml: Specify docker-compose to read yaml file
  • -d: Perform operations in the background
  • ps: Check the status of the container started based on docker-compose
  • logs: Check the logs during the process of starting the container Information for troubleshooting errors

Case:

Write the docker-compose.yaml file to start two containers : nginx, php

1) Prepare the environment

• Install epel
• Install docker-compose
• Restart docker
• Restart the firewall

[root@master ~]# yum install docker -y
[root@master ~]# yum install epel-release -y
[root@master ~]# yum install docker-compose -y
[root@master ~]# systemctl restart docker
[root@master ~]# systemctl restart firewalld

2) Create a yaml file

# 编写yam文件，在文件实现自动启动nginx容器
[root@worker1 ~]# vim docker-compose.yaml

version: '2'
services:
  web:
    image: nginx:1.17.10
    ports:
      - 80:80
    volumes:
      - /opt/html:/web
      - /opt/conf/nginx.conf:/etc/nginx/nginx.conf

• version: specify the version number, 2
• services: Set to start the service, a service is a docker container

2) nginx starts the container

[root@worker1 ~]# docker-compose up -d

View based on yaml The status of the container started by the file

[root@master ~]# docker-compose ps
   Name            Command          State         Ports       
--------------------------------------------------------------
root_web_1   nginx -g daemon off;   Up      0.0.0.0:80->80/tcp

• The status is mainly state: if it is UP, it means normal

View the log during the process of starting the container Information

[root@worker1 ~]# docker-compose logs

Close the container started based on the yaml file

[root@worker1 ~]# docker-compose down

3) Edit the yaml file based on the second step and start php Service

The first step: modify the yaml file

version: '2'services:
  web:
    image: nginx
    ports:
      - 80:80
    volumes:
      - /opt/html:/web
      - /opt/conf/nginx.conf:/etc/nginx/nginx.conf
    links:               # 指定php容器的名称
      - php
  php:                   # 此处需要和links中的值保持一致
    image: php:5.6-fpm
    container_name: php   # 此处需要和links中的值保持一致
    volumes:
      - /opt/php:/php

The second step: modify the nginx configuration file

[root@master ~]# vi /opt/conf/nginx.conf 
        location ~ \.php$ {
            root           /php;
            fastcgi_pass   php:9000;    # 指定php容器名称，docker会自动将名称转换成ip
            fastcgi_index  index.php;     
            fastcgi_param  SCRIPT_FILENAME  $document_root$fastcgi_script_name;
            include        fastcgi_params;
        }

Step 3: Start the service

[root@master ~]# docker-compose up -d
[root@master ~]# docker-compose ps
Name         Command                        State         Ports       
-----------------------------------------------------------------------
php          docker-php-entrypoint php-fpm   Up           9000/tcp          
root_web_1   nginx -g daemon off;            Up           0.0.0.0:80->80/tcp

Container orchestration application question 1

1 Prepare a Centos7 server and check that the network is normal

• 小

2 Check whether the server docker is running normally. If not, please install it

• 小

3 Please write the wordpress.yml template The file is in the correct format

4 Please create new services mysql and wordpress. The startup of wordpress depends on the mysql service

5 Mount the /opt/wordpress/data directory to /var/ of the mysql container Under the lib/mysql directory, do persistent storage!

6 MySQL initial information includes: root password, created database, ordinary user, ordinary user's password

7 WordPress database configuration is correct

8 WordPress does port mapping, will Port 80 of wordprss is mapped to port 8000 of the host machine

# 这个yaml文件要启动两个容器
version: '2'
services:
  # 第一个容器：wordpress容器
  wordpress:
    # 指定镜像名称
    image: wordpress
    # 将容器的80端口映射到宿主机的8000
    ports:
      - 8000:80
    # 设置将mysql容器的名称解析程序mysql容器的IP
    links:
      - mysql
    # 设置容器之间依赖关系，设置成必须先启动mysql容器才启动wordpress容器
    depends_on:
      - mysql
  # 第二个容器：MySQL容器
  mysql:
    # 指定镜像名名称是mysql
    image: mysql:5.6
    # 设置容器的名称的是mysql
    container_name: mysql
    # 设置逻辑卷挂载
    volumes: 
      - /opt/wordpress/data:/var/lib/mysql 
    # 设置mysql容器的环境变量
    environment:
      # 设置mysql容器中mysql的root密码为123
      MYSQL_ROOT_PASSWORD: 123
      # 为wordpress创建一个数据库，库名是wordpress
      MYSQL_DATABASE: wp   
      # 创建一个普通用户wp
      MYSQL_USER: wp
      # 为上面的普通用户设置密码是wp
      MYSQL_PASSWORD: wp

9 docker-compose successfully started each container and successfully accessed the wordpress page

[root@master ~]# docker-compose up -d
[root@master ~]# docker ps

• Browser access: http:/ /ip:8000

Recommended learning: "docker video tutorial"

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