Docker WARNING: Published ports are discarded when using host network mode

Question

I have a Springboot app that I have Dockerized. I have it exposed on port 8081, and can access it as expected.

http://<ipaddress>:8081

Problem

The Springboot app in the docker container needs to connect to a postgres database on the same host (not in a container), but it appears like it does not gave access to the host network.

Connection to localhost:5432 refused

Docker cmd:

docker run -t --rm -d -p 8081:8081 --name nexct-approval-service-container nexct-approval-service-image

So I have read in order to connect to the network, you can use:

--network host 

However, then it stops allowing access to the application itself (port 8081):

WARNING: Published ports are discarded when using host network mode

Question

How can I allow access to the SpringBoot app on port 8081 and allow the Springboot app access to the host network so it can connect to the database?

---

UPDATE

My database connection is defined in Spring Boot:

application.properties

spring.datasource1.driver-class-name=org.postgresql.Driver
spring.datasource1.jdbc-url=jdbc:postgresql://localhost:5432/pims
spring.datasource1.username=postgres
spring.datasource1.password=

MultipleDBConfig.java

@Configuration
@ComponentScan(basePackages = "com.nexct")
public class MultipleDBConfig {

    @Bean(name = "datasource1")
    @ConfigurationProperties("spring.datasource1")
    @Primary
    public DataSource dataSource1(){
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "datasource2")
    @ConfigurationProperties("spring.datasource2")
    public DataSource dataSource2(){
        return DataSourceBuilder.create().build();
    }
}

Answer 1

In my service, I replaced the references to localhost with host.docker.internal, and I was able to publish the container's ports with -p and connect to services on localhost without having to use --network host. My services references a .env file that has the hostnames, so I just created another .env file with the updated hostname.

Answer 2

You should change : localhost in connection string to :

172.17.0.1 its an IP address of containers network

Then check again.