How to access postgres-docker container other docker container without ip address - postgresql

Question

How to access postgres-docker container other docker container without ip address?
I want to store data in postgres by using myweb. in jar given host like localhost:5432/db..
Here my compose file:
version: "3"
services:
myweb:
build: ./myweb
container_name: app
ports:
- "8080:8080"
- "9090:9090"
networks:
- front-tier
- back-tier
depends_on:
- "postgresdb"
postgresdb:
build: ./mydb
image: ppk:postgres9.5
volumes:
- dbdata:/var/lib/postgresql
ports:
- "5432:5432"
networks:
- back-tier
volumes:
dbdata: {}
networks:
front-tier:
back-tier:

Answer 1

Instead of localhost:5432/db.. use postgresdb:5432/db.. connection string.
By default the container has the same hostname as the service name.
Here is my minimal working example, which is connecting a java client (boxfuse/flyway) with postgres server. The most important part is the heath check, which is delaying the start of the myweb container to the time when postgres is ready to accept connections.
Note that this can be directly executed by docker-compose up, it dosen't have any other dependencies. Both the images are from docker hub.
version: '2.1'
services:
myweb:
image: boxfuse/flyway
command: -url=jdbc:postgresql://postgresdb/postgres -user=postgres -password=123 info
depends_on:
postgresdb:
condition: service_healthy
postgresdb:
image: postgres
environment:
- POSTGRES_PASSWORD=123
healthcheck:
test: "pg_isready -q -U postgres"

Answer 2

That is the Docker Networking problem. The solution is to use postgresdb:5432/db in place of localhost:5432/db because the two service is in the same network named back-tier and docker deamon will use name service like a DNS name to make communication between the two container. I think that my solution will help you so.