[Cloud Native] Learning all modules in Docker-compose

 

compose module

        The template file is Composethe core of using , and there are many instruction keywords involved. But don’t worry, most of the commands and related parameters here docker runhave similar meanings.

The default template file name is docker-compose.yml, and the format is YAML format.

version: "3"
services:
  webapp:
    image: examples/web
    ports:
      \- "80:80"
    volumes:
      \- "/data"

Note that each service must imagespecify a mirror through the command or buildthe command (requires Dockerfile), etc. to automatically build and generate the mirror.

If buildthe command is used, Dockerfilethe options set in (for example: CMD, EXPOSE, VOLUME, ENVetc.) will be automatically obtained, and there is no need docker-compose.ymlto repeat the settings in .

The usage of each command is introduced below.

build

Specify Dockerfilethe path of the folder where is located (it can be an absolute path, or a path relative to the docker-compose.yml file). ComposeIt will be used to automatically build this image, and then use this image.

version: '3'
services:
  webapp:
  build: ./dir

You can also use contextthe directive to specify Dockerfilethe path to the folder where is located.

Use dockerfilethe directive to specify Dockerfilethe filename.

Use argthe directive to specify variables when building an image.

version: '3'
services:
  webapp:
  build:
    context: ./dir
    dockerfile: Dockerfile-alternate
    args:
      buildno: 1

Use to cache_fromspecify the cache of the built image

build:
  context: .
  cache_from:
     - alpine:latest
    - corp/web_app:3.14

cap_add, cap_drop

Specifies the kernel capacity allocation for the container.

For example, making a container have all capabilities can be specified as:

cap_add:

- ALL

The ability to remove NET_ADMIN can be specified as:

cap_drop:

- NET_ADMIN

command

Overrides the command that is executed by default when the container starts.

command: echo "hello world"

configs

For use only , please refer to the section Swarm modefor details .Swarm mode

cgroup_parent

Specifying a parent cgroupgroup means that the resource limits of that group will be inherited.

For example, a cgroup group name is created cgroups_1.

cgroup_parent: cgroups_1

container_name

Specify a container name. 项目名称_服务名称_序号This format will be used by default .

container_name: docker-web-container

Note: After specifying the container name, the service will not be able to scale (scale), because Docker does not allow multiple containers with the same name.

deploy

For use only , please refer to the section Swarm modefor detailsSwarm mode

devices

Specifies the device mapping relationship.

devices:

- "/dev/ttyUSB1:/dev/ttyUSB0"

depends_on

Solve the problem of container dependency and startup sequence. In the following example, it will start first redis dband then startweb

version: '3'
​
services:
  web:
    build: .
    depends_on:
     - db
     - redis
​
redis:
  image: redis
​
db:
  image: postgres

Note: webThe service does not wait for redis db"Full Start" before starting.

dns

Custom DNSserver. Can be a value or a list.

dns: 8.8.8.8

dns:
  - 8.8.8.8
  - 114.114.114.114

dns_search

Configure DNSsearch domains. Can be a value or a list.

dns_search: example.com

dns_search:
  \- domain1.example.com
  \- domain2.example.com

tmpfs

Mount a tmpfs file system to the container.

tmpfs: /run

tmpfs:
  \- /run
  \- /tmp

env_file

Get environment variables from a file, which can be a single file path or a list.

If docker-compose -f FILEthe Compose template file is specified by way, env_filethe path of the variable in will be based on the path of the template file.

If a variable name environmentconflicts with a directive, by convention, the latter takes precedence.

env_file: .env

env_file:
  \- ./common.env
  \- ./apps/web.env
  \- /opt/secrets.env

Each line in the environment variable file must conform to the format, supporting #comment lines beginning with .

# common.env: Set development environment

PROG_ENV=development

environment

Set environment variables. You can use both array and dictionary formats.

A variable with only a given name will automatically get the value of the corresponding variable on the host running Compose, which can be used to prevent unnecessary data leakage.

environment:
  RACK_ENV: development
  SESSION_SECRET:

environment:
  \- RACK_ENV=development
  \- SESSION_SECRET

If the variable name or value uses words that true|false，yes|noexpress the meaning of Boolean , it is best to put them in quotation marks to prevent YAML from automatically parsing certain content into corresponding Boolean semantics. These specific words, including

y|Y|yes|Yes|YES|n|N|no|No|NO|true|True|TRUE|false|False|FALSE|on|On|ON|off|Off|OFF

expose

Ports are exposed, but not mapped to the host, only accessed by connected services.

Only internal ports can be specified as parameters

expose:
 - "3000"
 - "8000"

external_links

Note: This command is deprecated.

Links to docker-compose.ymlcontainers outside of , not even Composeexternal containers managed by .

external_links:
 - redis_1
 - project_db_1:mysql
 - project_db_1:postgresql

extra_hosts

Similar to the parameter in Docker --add-host, specify additional host name mapping information.

extra_hosts:
 - "googledns:8.8.8.8"
 - "dockerhub:52.1.157.61"

/etc/hostsThe following two entries will be added to the file in the service container after startup .

8.8.8.8 googledns

52.1.157.61 dockerhub

healthcheck

Check whether the container is healthy and running with the command.

healthcheck:
  test: ["CMD", "curl", "-f", "http://localhost"]
  interval: 1m30s
  timeout: 10s
  retries: 3

image

Specified as an image name or image ID. If the mirror does not exist locally, Composean attempt will be made to pull the mirror.

image: free

image: orchardup/postgresql

image: a4bc65fd

labels

Add Docker metadata (metadata) information for the container. For example, auxiliary description information can be added to the container.

labels:
  com.startupteam.description: "webapp for a startup team"
  com.startupteam.department: "devops department"
  com.startupteam.release: "rc3 for v1.0"

links

Note: This command is deprecated.

logging

Configure logging options.

logging:
  driver: syslog
  options:
    syslog-address: "tcp://192.168.0.42:123"

Currently three log driver types are supported.

driver: "json-file"
driver: "syslog"
driver: "none"

optionsConfigure related parameters of the log driver.

options:
  max-size: "200k"
  max-file: "10"

network_mode

Set the network mode. Use the same value as for the parameter docker runof --network.

network_mode: "bridge"
network_mode: "host"
network_mode: "none"
network_mode: "service:[service name]"
network_mode: "container:[container name/id]"

networks

Configure the network the container is connected to.

version: "3"
services:
​
  some-service:
    networks:
      \- some-network
      \- other-network
​
networks:
  some-network:
  other-network:

pid

Share the process namespace with the host system. The containers with this option enabled, as well as the container and the host system, can access and operate each other through the process ID.

pid: "host"

ports

Expose port information.

Use the hostport:containerport (HOST:CONTAINER)format, or just specify the container's port (the host will choose a port randomly).

ports:
  - "3000"
  - "8000:8000"
  - "49100:22"
  - "127.0.0.1:8001:8001"

Note: When using *HOST:CONTAINER* format to map ports, if you use a container port less than 60 and don't put it in quotes, you may get wrong results, because this number format *YAML* is automatically parsed as base 60. *xx:yy* To avoid this kind of problem, it is recommended that all numeric strings use the string format enclosed in quotation marks.

secrets

Store sensitive data, such as mysqlservice passwords.

version: "3.1"
services:
​
mysql:
  image: mysql
  environment:
    MYSQL_ROOT_PASSWORD_FILE: /run/secrets/db_root_password
  secrets:
    - db_root_password
    - my_other_secret
​
secrets:
  my_secret:
    file: ./my_secret.txt
  my_other_secret:
    external: true

security_opt

Specifies the default attributes (user, role, type, level, etc.) of the container template label (label) mechanism. For example, configure the user name and role name of the label.

security_opt:
    - label:user:USER
    - label:role:ROLE

stop_signal

Set another signal to stop the container. By default it uses SIGTERM to stop the container.

stop_signal: SIGUSR1

sysctls

Configure container kernel parameters.

sysctls:
  net.core.somaxconn: 1024
  net.ipv4.tcp_syncookies: 0
​
sysctls:
  - net.core.somaxconn=1024
  - net.ipv4.tcp_syncookies=0

ulimits

Specifies the ulimits limit value for the container.

For example, specify the maximum number of processes as 65535, specify the number of file handles as 20000 (soft limit, which can be modified by the application at any time, and cannot exceed the hard limit) and 40000 (system hard limit, which can only be increased by the root user).

  ulimits:
    nproc: 65535
    nofile:
      soft: 20000
      hard: 40000

volumes

The path setting where the data volume is mounted. It can be set as host path ( HOST:CONTAINER) or data volume name ( VOLUME:CONTAINER), and access mode ( HOST:CONTAINER:ro).

The path in this directive supports relative paths.

volumes:
  - /var/lib/mysql
  - cache/:/tmp/cache
  - ~/configs:/etc/configs/:ro

If the path is a data volume name, the data volume must be configured in the file.

version: "3"
​
services:
  my_src:
    image: mysql:8.0
    volumes:
      - mysql_data:/var/lib/mysql
​
volumes:
  mysql_data:  

other instructions

In addition, there are domainname, entrypoint, hostname, ipc, mac_address, privileged, read_only, shm_size, restart, stdin_open, tty, user, working_dirinstructions including and so on, which are basically docker runconsistent with the functions of the corresponding parameters in .

Specify the entry file to be executed after the service container starts.

entrypoint: /code/entrypoint.sh

Specifies the username running the application in the container.

user: nginx

Specifies the working directory in the container.

working_dir: /code

Search the domain name, host name, mac address, etc. in the specified container.

domain name: your_website.com

hostname: test

mac_address: 08-00-27-00-0C-0A

Allow some privileged commands to run in the container.

privileged: true

Specifies that the restart policy after the container exits is always restart. alwaysThis command is very effective for keeping the service running all the time, and it is recommended to configure it as or in a production environment unless-stopped.

restart: always

Mounting the root filesystem of a container in read-only mode means that the contents of the container cannot be modified.

read_only: true

Open standard input, which can accept external input.

stdin_open: true

Simulate a pseudo-terminal.

tty: true

read variable

Compose template files support dynamic reading of host system environment variables and .envvariables in files in the current directory.

For example, the Compose file below will read ${MONGO_VERSION}the values ​​of variables from the environment in which it is run, and write them to the executed instructions.

version: "3"

services:

db:

image: "mongo:${MONGO_VERSION}"

If executed MONGO_VERSION=3.2 docker-compose up, a mongo:3.2mirrored container will be started; if executed, MONGO_VERSION=2.8 docker-compose upa mongo:2.8mirrored container will be started.

If there is .enva file in the current directory, docker-composevariables will be read from the file when the command is executed.

Create a new file in the current directory .envand write the following content.

# Support # comments

MONGO_VERSION=3.6

Executing docker-compose upwill start a mongo:3.6mirrored container.

Common modules

1. build command

Build the image according to the dockerfile before starting the container through docker-compose, and then start the container according to the built image

2.command

Override the command executed by default after the container starts

3.container_name

Used to specify the docker-compose startup container name Note: It is not recommended to specify the container name

4.depends_on

Solve the problem of container dependency and startup sequence

5.environment

Used to specify environment variables for container startup equivalent to docker run -e

6.env_file

Used to specify the environment variable file for container startup

7.expose

Used to specify the port number exposed by the container during image building docker run -p port: port

8.image

Used to specify the starting container to use the image docker run image (image name or ID)

9.networks

Used to specify the network docker run --network for container startup

10.ports

Used to specify host and container port mapping docker run -p

11.volumes

Used to specify the container directory mapping docker run -v in the host

12.restart

Used to specify whether the docker container always runs docker run --restart=always