Docker-compose does not recognice Postgres Host of SpringBoot App - postgresql

Question

I'am trying to use docker-compose with a springboot app(uses JPA) and a postgres database, I am kinda new using docker and I don't know what I am doing wrong.
Problem
When I build the springboot app, if I change
spring.datasource.url=jdbc:postgresql://localhost:5432/postgres(code that works) to host it in postgres container, spring.datasource.url=jdbc:postgresql://postgres:5432/postgres.
It throws me a PSQLException caused by: java.net.UnknownHostException: postgres.(More details below)
application.properties
server.port = 8080
## default connection pool
spring.datasource.hikari.connectionTimeout=20000
spring.datasource.hikari.maximumPoolSize=5
## PostgreSQL
spring.datasource.url=jdbc:postgresql://postgres:5432/postgres
spring.datasource.username=postgres
spring.datasource.password=postgres
spring.jpa.hibernate.ddl-auto=create
Exception
2020-06-22 19:07:10.597 INFO 16088 --- [ main] c.a.a.AnnotationToolApplicationTests : Starting AnnotationToolApplicationTests on DESKTOP-P1E07PA with PID 16088 (started by Pedro in C:\Users\Pedro\git\tfg\annotation-tool\annotation-tool)
2020-06-22 19:07:10.598 INFO 16088 --- [ main] c.a.a.AnnotationToolApplicationTests : No active profile set, falling back to default profiles: default
2020-06-22 19:07:11.584 INFO 16088 --- [ main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data JPA repositories in DEFAULT mode.
2020-06-22 19:07:11.719 INFO 16088 --- [ main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 120ms. Found 3 JPA repository interfaces.
2020-06-22 19:07:12.235 INFO 16088 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.transaction.annotation.ProxyTransactionManagementConfiguration' of type [org.springframework.transaction.annotation.ProxyTransactionManagementConfiguration] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2020-06-22 19:07:12.572 INFO 16088 --- [ main] o.hibernate.jpa.internal.util.LogHelper : HHH000204: Processing PersistenceUnitInfo [name: default]
2020-06-22 19:07:12.746 INFO 16088 --- [ main] org.hibernate.Version : HHH000412: Hibernate Core {5.4.10.Final}
2020-06-22 19:07:13.002 INFO 16088 --- [ main] o.hibernate.annotations.common.Version : HCANN000001: Hibernate Commons Annotations {5.1.0.Final}
2020-06-22 19:07:13.434 INFO 16088 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting...
2020-06-22 19:07:16.873 ERROR 16088 --- [ main] com.zaxxer.hikari.pool.HikariPool : HikariPool-1 - Exception during pool initialization.
org.postgresql.util.PSQLException: The connection attempt failed.
at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:292) ~[postgresql-42.2.9.jar:42.2.9]
...
at org.apache.maven.surefire.booter.ForkedBooter.execute(ForkedBooter.java:126) ~[surefire-booter-2.22.2.jar:2.22.2]
at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:418) ~[surefire-booter-2.22.2.jar:2.22.2]
Caused by: java.net.UnknownHostException: postgres
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:184) ~[na:1.8.0_222]
docker-compose.yml
version: '3'
services:
# SpringBoot App
postgres:
image: "postgres:9.6-alpine"
ports:
- 5432:5432
volumes:
- apiDB:/var/lib/postgresql/data
environment:
- POSTGRES_DB=postgres
- POSTGRES_USER=postgres
- POSTGRES_PASSWORD=postgres
api:
build: ./annotation-tool
ports:
- 8080:8080
depends_on:
- postgres
client:
container_name: client-container
build: ./client
ports:
- 8081:8081
volumes:
apiDB:
Api Dockerfile
FROM maven:3.6.1-jdk-8-slim AS build
RUN mkdir -p /workspace
WORKDIR /workspace
COPY pom.xml /workspace
COPY src /workspace/src
RUN mvn -f pom.xml clean package
FROM openjdk:8
COPY --from=build /workspace/target/*.jar app.jar
EXPOSE 8080
ENTRYPOINT ["java","-jar","app.jar"]
Things that I think that happened/ tried
Maybe the DNS is not working, but I don't know how I can solve it
I tried differents docker-compose and Dockerfiles and it doesn't work
If I run the docker-compose the postgres container is created succesfully
I tried changing the url host to postgres-backend as my container was named that way
I tried by using links between my components.

Answer 1

I think springboot application is finding postgres db before its container is getting up...you can add depends_on property in springboot container ..so the postgres container starts first then springboot
version: '3'
services:
# SpringBoot App
postgres:
image: "postgres:9.6-alpine"
ports:
- 5432:5432
volumes:
- apiDB:/var/lib/postgresql/data
environment:
- POSTGRES_DB=postgres
- POSTGRES_USER=postgres
- POSTGRES_PASSWORD=postgres
api:
build: ./annotation-tool
ports:
- 8080:8080
depends_on:
- postgres
client:
container_name: client-container
build: ./client
ports:
- 8081:8081
volumes:
apiDB:

Answer 2

I don't know if I am thinking to simple right know but all container of your docker-compose file run on the same host, right? So then your url should point to jdbc:postgresql://localhost:5432/postgres.

Answer 3

I don't know if you already solved the problem but have you tried to use a bridge network on the setup?
version: '3'
services:
# SpringBoot App
postgres:
image: "postgres:9.6-alpine"
ports:
- 5432:5432
volumes:
- apiDB:/var/lib/postgresql/data
environment:
- POSTGRES_DB=postgres
- POSTGRES_USER=postgres
- POSTGRES_PASSWORD=postgres
networks:
- database-network
api:
build: ./annotation-tool
ports:
- 8080:8080
depends_on:
- postgres
networks:
- database-network
client:
container_name: client-container
build: ./client
ports:
- 8081:8081
networks:
database-network:
driver: bridge
external: false
volumes:
apiDB: