I’m learning Docker and I have a question that is certainly simple, but I haven’t found it anywhere yet: I want a Keycloak container to connect to the SQL Server database that is installed locally on my machine – that is, the database data is not in container.

I saw in some places that if a container wanted to connect to a specific port on my machine it could use host.docker.internal. But would this work for databases?

See, I set up this very simple docker-compose to test this solution, but I haven’t managed to do it yet, because whenever the container starts running, an error is returned.

docker-compose

services:
  keycloak:
    image: quay.io/keycloak/keycloak:latest
    environment:
      KC_DB: mssql
      KC_DB_URL: jdbc:sqlserver://host.docker.internal:1433;databaseName=Keycloak;encrypt=false;trustServerCertificate=true;loginTimeout=30
      KC_DB_USERNAME: xxx
      KC_DB_PASSWORD: yyy
      KEYCLOAK_ADMIN: admin
      KEYCLOAK_ADMIN_PASSWORD: admin
    ports:
      - "4000:8080"
    command:
      - start-dev
    restart: always

Container logs:

Updating the configuration and installing your custom providers, if any. Please wait.
2024-07-21 01:19:18,531 INFO  [io.qua.dep.QuarkusAugmentor] (main) Quarkus augmentation completed in 4866ms
2024-07-21 01:19:21,968 INFO  [org.infinispan.CONTAINER] (ForkJoinPool.commonPool-worker-1) ISPN000556: Starting user marshaller 'org.infinispan.jboss.marshalling.core.JBossUserMarshaller'
2024-07-21 01:19:26,794 WARN  [org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator] (JPA Startup Thread) HHH000342: Could not obtain connection to query metadata: java.lang.NullPointerException: Cannot throw exception because the return value of "java.util.function.BiFunction.apply(Object, Object)" is null
        at org.hibernate.resource.transaction.backend.jta.internal.JtaIsolationDelegate.doTheWork(JtaIsolationDelegate.java:202)
        at org.hibernate.resource.transaction.backend.jta.internal.JtaIsolationDelegate.lambda$delegateWork$3(JtaIsolationDelegate.java:91)
        at org.hibernate.resource.transaction.backend.jta.internal.JtaIsolationDelegate.doInSuspendedTransaction(JtaIsolationDelegate.java:123)
        at org.hibernate.resource.transaction.backend.jta.internal.JtaIsolationDelegate.delegateWork(JtaIsolationDelegate.java:88)
        at org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator.getJdbcEnvironmentUsingJdbcMetadata(JdbcEnvironmentInitiator.java:276)
        at org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator.initiateService(JdbcEnvironmentInitiator.java:107)
        at org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator.initiateService(JdbcEnvironmentInitiator.java:68)
        at org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.initiateService(StandardServiceRegistryImpl.java:130)
        at org.hibernate.service.internal.AbstractServiceRegistryImpl.createService(AbstractServiceRegistryImpl.java:263)
        at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:238)
        at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:215)
        at org.hibernate.engine.jdbc.internal.JdbcServicesImpl.configure(JdbcServicesImpl.java:52)
        at org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:136)
        at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:247)
        at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:215)
        at org.hibernate.boot.internal.SessionFactoryOptionsBuilder.<init>(SessionFactoryOptionsBuilder.java:276)
        at io.quarkus.hibernate.orm.runtime.recording.PrevalidatedQuarkusMetadata.buildSessionFactoryOptionsBuilder(PrevalidatedQuarkusMetadata.java:70)
        at io.quarkus.hibernate.orm.runtime.boot.FastBootEntityManagerFactoryBuilder.build(FastBootEntityManagerFactoryBuilder.java:84)
        at io.quarkus.hibernate.orm.runtime.FastBootHibernatePersistenceProvider.createEntityManagerFactory(FastBootHibernatePersistenceProvider.java:72)
        at jakarta.persistence.Persistence.createEntityManagerFactory(Persistence.java:80)
        at jakarta.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
        at io.quarkus.hibernate.orm.runtime.JPAConfig$LazyPersistenceUnit.get(JPAConfig.java:157)
        at io.quarkus.hibernate.orm.runtime.JPAConfig$1.run(JPAConfig.java:64)
        at java.base/java.lang.Thread.run(Thread.java:1583)

2024-07-21 01:19:27,287 INFO  [org.keycloak.broker.provider.AbstractIdentityProviderMapper] (main) Registering class org.keycloak.broker.provider.mappersync.ConfigSyncEventListener
2024-07-21 01:19:27,303 INFO  [org.keycloak.connections.infinispan.DefaultInfinispanConnectionProviderFactory] (main) Node name: node_489463, Site name: null
2024-07-21 01:19:32,311 INFO  [com.arjuna.ats.jbossatx] (main) ARJUNA032014: Stopping transaction recovery manager
2024-07-21 01:19:32,372 ERROR [org.keycloak.quarkus.runtime.cli.ExecutionExceptionHandler] (main) ERROR: Failed to start server in (development) mode
2024-07-21 01:19:32,372 ERROR [org.keycloak.quarkus.runtime.cli.ExecutionExceptionHandler] (main) ERROR: Failed to obtain JDBC connection
2024-07-21 01:19:32,372 ERROR [org.keycloak.quarkus.runtime.cli.ExecutionExceptionHandler] (main) ERROR: Acquisition timeout while waiting for new connection

I’ve already tried changing the connection string and also using network_mode: host but nothing worked.