1 format of configuration file

• An example docker-compose.yml

  services:
    elasticsearch:
      image: elasticsearch:7.14.2
      container_name: es
      environment:
        discovery.type: single-node
        ES_JAVA_OPTS: "-Xms512m -Xmx512m"
      ports:
        - "9200:9200"
        - "9300:9300"
      healthcheck:
        test: ["CMD-SHELL", "curl --silent --fail localhost:9200/_cluster/health || exit 1"]
        interval: 10s
        timeout: 10s
        retries: 3
      networks:
        - elastic
    logstash:
      image: logstash:7.14.2
      container_name: log
      environment:
        discovery.seed_hosts: logstash
        LS_JAVA_OPTS: "-Xms512m -Xmx512m"
      volumes:
        - ./logstash/pipeline/logstash-nginx.config:/usr/share/logstash/pipeline/logstash-nginx.config
        - ./logstash/nginx.log:/home/nginx.log
      ports:
        - "5000:5000/tcp"
        - "5000:5000/udp"
        - "5044:5044"
        - "9600:9600"
      depends_on:
        - elasticsearch
      networks:
        - elastic
      command: logstash -f /usr/share/logstash/pipeline/logstash-nginx.config
    kibana:
      image: kibana:7.14.2
      container_name: kib
      ports:
        - "5601:5601"
      depends_on:
        - elasticsearch
      networks:
        - elastic
  networks:
    elastic:
      driver: bridge
  

2. Explain the services section in detail

2.1 image

• web user defined service name
• Image can be specified as the image name or image ID. if it does not exist locally, it will automatically try to pull

services:
  web:
    image: redis

2.2 build

• The service startup can be based on 2.1 image or Dockerfile. The build task will be executed when the service is started up.
• The sub tag context sets the context root directory
• The sub tag Dockerfile specifies the Dockerfile file
• The child tag args specifies the environment variables used during the build

  services:
    web:
      build:
        context: ../
        dockerfile: Dockerfile
        args:
        	- buildno=1
        	- password=123456
  

• Specifying both the image and build tags will name the built image after the image

  services:
    web:
      build: .
      image: webapp:tag
  

2.3 command

• Using command overrides the command to be executed by default after the image is started

  services:
    web:
      command: redis-server /etc/redis/redis.conf --appendonly yes
  

  services:
    web:
      command: ["redis-server", "/etc/redis/redis.conf", "--appendonly", "yes"]
  

2.4 container_name

• The format of docker compose startup container name is: < project name > < service name > < serial number >
• You can also use container_name custom container name

  services:
    web:
      container_name: redis-6379
  

2.5 depends_on

• Generally, in a project, the container needs to have a specific start sequence, otherwise it will fail to start due to dependency problems.
• Example: if you start the application container without starting the database, the application container will exit because the database cannot be found
• Solution: dependencies_ on

  services:
    web: 
      build: .
      depends_on:
        - db
        - redis
    redis:
      image: redis:latest
    db:
      image: mysql:5.7
  

2.6 dns

• The same purpose as the -- dns parameter in docker run

  services:
    web: 
      dns: 8.8.8.8
  

  services:
    web: 
      dns: 
        - 8.8.8.8
        - 114.114.114.114
  

2.7 entrypoint

• There is an instruction entrypoint in Dockerfile to specify the access point. The definition of entrypoint in docker-compose.yml will overwrite the definition in Dockerfile

  services:
    web: 
      entrypoint: java -jar app.jar --spring.profiles.active=release 
  

  services:
    web: 
      entrypoint: 
        - java
        - -jar
        - app.jar
        - --spring.profiles.active=release 
  

2.8 environment

• It is equivalent to the function of docker run -e

  services:
    mysql: 
      image: mysql
      environment:
        - MYSQL_ROOT_PASSWORD=123456
        - MYSQL_ALLOW_EMPTY_PASSWORD=yes 
  

2.9 extra_hosts

• Adding the host name mapping is equivalent to adding records to / etc/hosts, and is equivalent to the function of docker run -- add host

  services:
    web: 
      extra_hosts: 
        - webnode1:192.168.171.100
        - webnode2:192.168.171.101
  

• This is what / etc/hosts in the container can see

  192.168.171.100 webnode1
  192.168.171.101 webnode2
  

2.10 ports

• The port mapping label is equivalent to the docker run -p function

  services:
    web: 
      ports:
        - 80:80
        - 1180:1180 
  

2.11 volumes

• Mounting a directory or an existing data volume container is equivalent to the docker run -v function
• HOST:CONTAINER HOST:CONTAINER:ro,: ro means read-only, and the default is read-write

  services:
    web: 
      volumes:
        - /usr/share/zoneinfo/Asia/Shanghai:/etc/localtime:ro
        - ./webdist:/home/webdist
  

2.12 networks

• Join the specified network

  services:
    web:
      networks:
        - web-net
        - backend-net
  

2.13 cap_add,cap_drop

• Add or remove the kernel functionality of the container

2.14 cgroup_parent

• Specifies the parent cgroup of the container

2.15 others

• There are other single value Tags: user working_dir hostname privileged restart

  services:
    web:
      user: mysql
      working_dir: /home/webdist
      hostname: webnode
      privileged: true
      restart: always
  

Reference article:

https://www.jianshu.com/p/2217cfed29d7