How to connect to DB? What is hostname of another running template?

[Serhioromano]

I have Logto template running. It have 2 containers, app and postgres. I created another service pgAdmin. It works fine. Now I want to connect to postgres of logto service.

This is my pgAdmin service

services:
  pgadmin:
    image: dpage/pgadmin4:2025-08-20-1
    restart: unless-stopped
    environment:
      - PGADMIN_DEFAULT_EMAIL=${PGADMIN_DEFAULT_EMAIL}
      - PGADMIN_DEFAULT_PASSWORD=${PGADMIN_DEFAULT_PASSWORD}
      - PGADMIN_CONFIG_SERVER_MODE=False
      - PGADMIN_CONFIG_MASTER_PASSWORD_REQUIRED=False
    volumes:
      - pgadmin-data:/var/lib/pgadmin

networks:
  dokploy-network:
    external: true

volumes:
  pgadmin-data:

But whatever I enter in hostname when connect new DB fails with cannot resolve. What is hostname of postgres service that I can access in another service?

My logto service looks like this

services:
  app:
    depends_on:
      postgres:
        condition: service_healthy
    image: ghcr.io/logto-io/logto:1.27.0
    entrypoint: ["sh", "-c", "npm run cli db seed -- --swe && npm start"]
    ports:
      - 3001
      - 3002

    environment:
      TRUST_PROXY_HEADER: 1
      DB_URL: postgres://logto:${LOGTO_POSTGRES_PASSWORD}@postgres:5432/logto
      ENDPOINT: ${LOGTO_ENDPOINT}
      ADMIN_ENDPOINT: ${LOGTO_ADMIN_ENDPOINT}
    volumes:
      - logto-connectors:/etc/logto/packages/core/connectors
  postgres:
    image: postgres:17-alpine
    user: postgres

    environment:
      POSTGRES_USER: logto
      POSTGRES_PASSWORD: ${LOGTO_POSTGRES_PASSWORD}
    volumes:
      - postgres-data:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready", "-U", "logto"]
      interval: 10s
      timeout: 5s
      retries: 5

networks:
  dokploy-network:
    external: true

volumes:
  logto-connectors:
  postgres-data:

[djsisson]

they need to be in the same docker network in order to connect using a service name

[Serhioromano]

Thank you. I added

networks:
  - dokploy-network

to both services and now I am able to connect them by hostname. Perfect. So yeasy :)