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docker-compose ports vs expose

Ports

Ports is defined as

Exports ports. Either specify both ports (HOST:CONTAINER), or just the container port (a random host port will be chosen)

  • Ports mentioned in docker-compose.yml wil be shared amount different services started by the docker-compose
  • Ports will be exposed to the host machine to a random port or a given port

docker-compose.yml

mysql:
  image: mysql:5.7
  ports:
    - "3306"

docker-compose ps

  Name                     Command               State            Ports
-------------------------------------------------------------------------------------
  mysql_1       docker-entrypoint.sh mysqld      Up      0.0.0.0:32769->3306/tcp

expose

Expose is defined as

Expose ports without publishing them to the host machine - they'll only be accessible to linked services. Only the internal port can be specified

  • Ports are not exposed to host machine, only exposed to other services
mysql:
  image: mysql:5.7
  expose:
    - "3306"

 Name                  Command             State    Ports
---------------------------------------------------------------
 mysql_1      docker-entrypoint.sh mysqld   Up      3306/tcp

References