为什么docker-compose不会为mongo打开端口？

Question

I can't get docker-compose to open port 27017 or at least allow rest to make a connection with mongo.

Anyway, the following works just fine: docker run -p 27017:27017 mongo:latest

This is my docker-compose.yml :

version: '3.5'
services:
  mongo:
    container_name: mongo
    image: mongo:latest
    ports:
      - "27017:27017"

  web:
    container_name: web
    build:
      context: ./src/main/ui/
    ports:
      - "80:80"

  rest:
    container_name: rest
    links:
      - mongo
    build:
      context: .
    ports:
      - "8080:8080"
    entrypoint: [ "java", "-jar", "/rest/build/libs/pBlog.jar" ]

Output of docker ps (as you can see, port 27017 is closed in mongo):

▶ docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                    NAMES
08f5dfb7acb8        2d8ccd24817e        "java -jar /rest/bui…"   About an hour ago   Up 11 minutes       0.0.0.0:8080->8080/tcp   pblog_rest_1
4929257802c5        mongo               "docker-entrypoint.s…"   2 hours ago         Up 11 minutes       27017/tcp                pblog_mongo_1
816a60eb9c7f        pblog_web           "nginx -g 'daemon of…"   3 days ago          Up 11 minutes       0.0.0.0:80->80/tcp       pblog_web_1

Output of docker logs <mongoContainerId> : https://pastebin.com/raw/XZGUh4UC

Output of docker logs <restContainerId> : https://pastebin.com/raw/F7rwKMCe (it isn't able to connect to the database)

I've tried making shell script to run mongo inside container. Also tried to edit ports section in mongo service to "1-65535:1-65535" (this should open all ports) - won't work either. Deleting ports section and adding expose: - 27017 gives the same result.

It seems like mongo image somehow forces docker to close ports.

Answer 1

You need to open ports only if you want to connect from the outside, which can be useful but for your scenario it is not necessary. Your rest container should be able to find mongo under this URL mongo:27017. Since each container sees itself as localhost, it won't see other containers on localhast at all.

Note: You have opened the port sucessfully, and you should be able to ping it from your PC, but from the inside of containers, the network looks differently.