Running Spring Boot docker instance with Postgres docker instance

Question

I'm attempting to run a Spring Boot app that connects a Postgres DB using:

docker-compose.yml (for Postgres) :

  version: '3'
  services:
  postgres-db:
  container_name: postgres-db
  image: postgres:latest
  restart: always
  ports:
  - "5432:5432"
  environment:
  POSTGRES_USER: my_user
  POSTGRES_PASSWORD: my_password
  POSTGRES_DB: shorten-db

To run the Postgres DB:

docker-compose up

.Dockerfile (for the Spring Boot app) :

  FROM openjdk:12-jdk-alpine
  RUN addgroup -S spring && adduser -S spring -G spring
  USER spring:spring
  ARG JAR_FILE=target/*.jar
  COPY ${JAR_FILE} app.jar
  ENTRYPOINT ["java","-jar","/app.jar"]

In order to run the Spring app using Docker I use:

  mvn package
  
  docker build -t url-shorten/url-shorten-docker .
  
  docker run -p 8080:8080 url-shorten/url-shorten-docker

But I receive the error when starting when running above docker command:

Caused by: org.postgresql.util.PSQLException: Connection to localhost:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.

In Spring application.properties I connect to the DB using:

spring.datasource.url=jdbc:postgresql://localhost:5432/shorten-db

I think this error is due to the Spring Boot app is running in a different container to DB so it cannot find the DB on localhost. Is there an idiomatic way of connecting the Spring Book docker container to the DB container. Or do I have do access the IP address of my machine and use this address to connect to the Postgres DB running on Docker?

If you're running a container in the same network, it can be accessed by its container name, e.g. postgres-db:5432 — jAC
– jAC, Commented Sep 2, 2020 at 12:55
The answers that you got (to use the container name postgres-db directly) will work only if you run the containers at the same user-defined bridge. The way you are doing it now, the db container runs at the bridge created automatically when you docker-compose up and the other (with docker run ...) will run at the default bridge. — tgogos
– tgogos, Commented Sep 2, 2020 at 13:03
More here: Differences between user-defined bridges and the default bridge — tgogos
– tgogos, Commented Sep 2, 2020 at 13:04
I would put the Spring-boot container details inside the docker-compose.yaml file and let docker-compose deal with the networking. When you docker-compose up / down it creates/deletes automatically a custom bridge for your convenience. Check more here: Networking in Compose — tgogos
– tgogos, Commented Sep 2, 2020 at 13:09
The other option is what you are proposing, yes, to deal with the networks yourself a little bit more "manually". — tgogos
– tgogos, Commented Sep 2, 2020 at 13:20

Nikolai Shevchenko · Accepted Answer · 2020-09-02 12:56:02Z

1

Yes, you can't use localhost in this situation

spring.datasource.url=jdbc:postgresql://postgres-db:5432/shorten-db

answered Sep 2, 2020 at 12:56

Nikolai Shevchenko

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Łukasz Olszewski · Accepted Answer · 2020-09-02 12:55:34Z

1

In Spring application.properties, try to change DB config to:

spring.datasource.url=jdbc:postgresql://postgres-db:5432/shorten-db

In container networks, You need to use the container name as a host.

answered Sep 2, 2020 at 12:55

Łukasz Olszewski

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Igor Amelin · Accepted Answer · 2020-09-02 12:56:18Z

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You can add both DB and app containers to one Docker network and change PostgreSQL host in datasource URL to postgres-db. Then Spring app will work with your DB.

answered Sep 2, 2020 at 12:56

Igor Amelin

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