How do I access a postgresql DB that was setup with docker-compose?-CodePudding

I use the following docker-compose.yml file:

version: '3.8'

services:
  db:
    image: postgres:13-alpine
    volumes:
      - postgres_data:/var/lib/postgresql/data/
    expose:
      - 5432
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=postgres
      - POSTGRES_DB=testdb
volumes:
  postgres_data:

I bring it up with docker-compose up -d --build. Now when I try to access it from Python, say, with psycopg2 the following errors show up

>>> conn = psycopg2.connect(host="localhost", database="testdb", user="postgres", password="postgres")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.9/site-packages/psycopg2/__init__.py", line 122, in connect
    conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
psycopg2.OperationalError: connection to server at "localhost" (::1), port 5432 failed: Connection refused
    Is the server running on that host and accepting TCP/IP connections?
connection to server at "localhost" (127.0.0.1), port 5432 failed: Connection refused
    Is the server running on that host and accepting TCP/IP connections?

>>> conn = psycopg2.connect(host="db", database="testdb", user="postgres", password="postgres")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.9/site-packages/psycopg2/__init__.py", line 122, in connect
    conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
psycopg2.OperationalError: could not translate host name "db" to address: nodename nor servname provided, or not known

Could you help me to resolve that?

CodePudding user response：

The problem is that expose does not publish the ports to the host machine. They are only accessible to linked services.

You have to manually publish the ports:

docker-compose run -d -p 5432:5432 db

CodePudding user response：

Instead of using expose us this instead:

ports:
  - "5432:5432"

This defines the port forwarding to the docker container

CodePudding user response：

You should remove expose option from your docker-compose.yml file and add ports option such as:

ports:
  -"5432:5432"

Then you can connect to database by host localhost from your application.