configure-different-host-and-container-ports.md

Configure Different Host And Container Ports

A docker-compose.yml file that sets up something like a PostgreSQL service will proxy a port from your host machine to a port on the docker container.

A basic PostgreSQL service will look like this tying 5432 to 5432 under the ports section.

version: "3.7"
services:
  postgres:
    image: postgres:latest
    restart: always
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=postgres
      - POSTGRES_DB=postgres
    ports:
      - "5432:5432"
    volumes:
      - ./postgres-data:/var/lib/postgresql/data

Requests like queries from a psql instance that we send to localhost:5432 will be proxied to docker-container:5432.

Since those numbers are the same on both sides, it's not necessarily clear which is which. The left is the host and the right is the container -- [host-port]:[container-port].

If you need to use a port other than 5432 on your host machine (e.g. maybe you're running multiple Postgres servers at once), then you can just change the port number on the left side. How about 9876:5432.