Postgresql Connection Refused in docker container, But Success on server - spring

Question

I try to connect spring app with postgresql.
When I run my app directly on server(not container), Connection success.
java -jar app.jar
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.4.5)
2021-07-05 14:10:58.348 INFO 334534 --- [ main] com.studb.poemNote.PoemNoteApplication : Starting PoemNoteApplication v1 using Java 11.0.11 on ip-172-31-3-67 with PID 334534 (/home/ubuntu/poemnote/poemNote/target/poemNote-1.jar started by ubuntu in /home/ubuntu/poemnote/poemNote)
2021-07-05 14:10:58.355 INFO 334534 --- [ main] com.studb.poemNote.PoemNoteApplication : No active profile set, falling back to default profiles: default
2021-07-05 14:11:00.447 INFO 334534 --- [ main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data JDBC repositories in DEFAULT mode.
2021-07-05 14:11:00.498 INFO 334534 --- [ main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 46 ms. Found 0 JDBC repository interfaces.
2021-07-05 14:11:01.903 INFO 334534 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 9000 (http)
2021-07-05 14:11:01.936 INFO 334534 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2021-07-05 14:11:01.936 INFO 334534 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.45]
2021-07-05 14:11:02.095 INFO 334534 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2021-07-05 14:11:02.095 INFO 334534 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 3595 ms
2021-07-05 14:11:02.945 INFO 334534 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting...
2021-07-05 14:11:03.197 INFO 334534 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Start completed.
2021-07-05 14:11:04.497 INFO 334534 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2021-07-05 14:11:04.762 INFO 334534 --- [ main] o.s.b.a.w.s.WelcomePageHandlerMapping : Adding welcome page: class path resource [static/index.html]
2021-07-05 14:11:05.241 INFO 334534 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 9000 (http) with context path ''
2021-07-05 14:11:05.267 INFO 334534 --- [ main] com.studb.poemNote.PoemNoteApplication : Started PoemNoteApplication in 8.396 seconds (JVM running for 9.694)
^C2021-07-05 14:11:13.986 INFO 334534 --- [extShutdownHook] o.s.s.concurrent.ThreadPoolTaskExecutor : Shutting down ExecutorService 'applicationTaskExecutor'
But when i run container, connection fail like below
docker run -p port:port
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.4.5)
2021-07-05 14:12:37.130 INFO 1 --- [ main] com.studb.poemNote.PoemNoteApplication : Starting PoemNoteApplication v1 using Java 11.0.11 on de04c6a415a5 with PID 1 (/app/BOOT-INF/classes started by root in /app)
2021-07-05 14:12:37.139 INFO 1 --- [ main] com.studb.poemNote.PoemNoteApplication : No active profile set, falling back to default profiles: default
2021-07-05 14:12:38.997 INFO 1 --- [ main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data JDBC repositories in DEFAULT mode.
2021-07-05 14:12:39.055 INFO 1 --- [ main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 47 ms. Found 0 JDBC repository interfaces.
2021-07-05 14:12:40.351 INFO 1 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 9000 (http)
2021-07-05 14:12:40.383 INFO 1 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2021-07-05 14:12:40.383 INFO 1 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.45]
2021-07-05 14:12:40.516 INFO 1 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2021-07-05 14:12:40.516 INFO 1 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 3260 ms
2021-07-05 14:12:41.248 INFO 1 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting...
2021-07-05 14:12:52.405 ERROR 1 --- [ 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:315) ~[postgresql-42.2.19.jar:42.2.19]
at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:51) ~[postgresql-42.2.19.jar:42.2.19]
at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:223) ~[postgresql-42.2.19.jar:42.2.19]
at org.postgresql.Driver.makeConnection(Driver.java:465) ~[postgresql-42.2.19.jar:42.2.19]
at org.postgresql.Driver.connect(Driver.java:264) ~[postgresql-42.2.19.jar:42.2.19]
at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:138) ~[HikariCP-3.4.5.jar:na]
at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:358) ~[HikariCP-3.4.5.jar:na]
at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:206) ~[HikariCP-3.4.5.jar:na]
at com.zaxxer.hikari.pool.HikariPool.createPoolEntry(HikariPool.java:477) ~[HikariCP-3.4.5.jar:na]
It's my dockerfile
FROM adoptopenjdk:11-jre-hotspot as builder
WORKDIR app
ARG JAR_FILE=target/*jar
COPY ${JAR_FILE} app.jar
RUN java -Djarmode=layertools -jar app.jar extract
FROM adoptopenjdk:11-jre-hotspot
WORKDIR app
COPY --from=builder app/dependencies/ ./
COPY --from=builder app/spring-boot-loader/ ./
COPY --from=builder app/snapshot-dependencies/ ./
COPY --from=builder app/application/ ./
EXPOSE 9000
ENTRYPOINT ["java", "org.springframework.boot.loader.JarLauncher"]
I can't understand why it does...
I try run container '--network host' but it's failed.

Answer 1

Postgresql running inside container on the same host
In case postgresql is also running inside a container of the same host, you need to make sure that they share the same network and that the containers can reach each other.
Check configured networks of the container:
docker inspect <container> -f "{{json .NetworkSettings.Networks }}"
Check if you can reach one container from the another:
docker exec -u 0 <container1> ping <container2> -c2
In case they are not on the same network, you need to create the network first and then connect the containers to it:
docker network create <network>
and
docker network connect <network> <container>
Postgresql running directly on the host
In case postgresql is running directly on the host where your docker container is running, you need to make sure that you can reach the host system from your container. Try to add the following command when you start the container
--add-host=host.docker.internal:host-gateway
Useful Links:
How to access host port from docker container
Docker : How to find the network my container is in?
https://docs.docker.com/network/
https://docs.docker.com/network/bridge/