[Enhancement]: Containers declared with @Container can not depend od each other mapped ports using method withEnv(). Use Supplier<String> for env values

Module

Core

Proposal

When configuring test case like:

    @Container
    public static final GenericContainer<?> ACTIVE_MQ_CONTAINER = new GenericContainer<>(ACTIVE_MQ_IMAGE)
            .withExposedPorts(61616, 8161, 5672)
            .withExtraHost("host.docker.internal", "host-gateway")
            .withAccessToHost(true)
            .withNetwork(NETWORK);
            
            
    @Container
    private static final GenericContainer<?> MOCK_SERVER = new GenericContainer<>(MOCK_SERVER_IMAGE)
            .withExposedPorts(1080)
            .withNetwork(NETWORK)
            .withExtraHost("host.docker.internal", "host-gateway")
            .withAccessToHost(true); 
            
    @Container
    private static final GenericContainer MS_SQL_CONTAINER = new GenericContainer<>(MS_SQL_IMAGE)
            .withEnv("ACCEPT_EULA", "Y")
            .withEnv("SA_PASSWORD", "yourStrong(!)Password")
            .withNetwork(NETWORK)
            .withExposedPorts(1433)
            .withNetworkAliases("base");

    @Container
    private static final GenericContainer<?> APP_SERVER = new GenericContainer<>(APP_IMAGE)
            .dependsOn(MS_SQL_CONTAINER,MOCK_SERVER, ACTIVE_MQ_CONTAINER)
            .withEnv("ConnectionStrings__AzureServiceBus", "amqp://host.docker.internal:" + ACTIVE_MQ_CONTAINER.getMappedPort(5672))
...

dependency will fail because the first three Testcontainers are not started and line:
.withEnv("ConnectionStrings__AzureServiceBus", "amqp://host.docker.internal:" + ACTIVE_MQ_CONTAINER.getMappedPort(5672))
will throw an error because can not read the value from the not-started container.

Automated init sequence when using @Container annotation can be replaced with:

 private static final GenericContainer<?> FIRST_CONTAINER = new GenericContainer<>(
        JUnitJupiterTestImages.HTTPD_IMAGE).withExposedPorts(80);

    private static final GenericContainer<?> SECOND_CONTAINER = new GenericContainer<>(
        JUnitJupiterTestImages.HTTPD_IMAGE).withExposedPorts(80);

    private static final GenericContainer<?> APP_CONTAINER = new GenericContainer<>(JUnitJupiterTestImages.HTTPD_IMAGE)
        .dependsOn(FIRST_CONTAINER, SECOND_CONTAINER).withExposedPorts(80)
              .withEnv(FIRST_DEPENDENCY_ENV_KEY, String.valueOf(FIRST_CONTAINER.getFirstMappedPort()))
              .withEnv(SECOND_DEPENDENCY_ENV_KEY, String.valueOf(SECOND_CONTAINER.getFirstMappedPort()));

    @BeforeAll
    public static void setupWithException() {
                FIRST_CONTAINER.start();
                SECOND_CONTAINER.start();
                APP_CONTAINER.start();

A possible solution is to defer the resolution of dependency of ACTIVE_MQ_CONTAINER.getMappedPort(5672)) to a read stage of the dependent container (APP_SERVER container startup time).

Using Supplier<String> instead of String for type of value in Env Map. With this change, the example from above will work.

The current workaround is to start containers manually without @ Container annotation and using manually written checks 'is container started'. Containers in the test class must be declared in an ordered way.
Code snippet for manual container start-check:

    public static final GenericContainer<?> ACTIVE_MQ_CONTAINER;

    static {
        ACTIVE_MQ_CONTAINER = new GenericContainer<>(ACTIVE_MQ_IMAGE)
                .withExposedPorts(61616, 8161, 5672)
                .withExtraHost("host.docker.internal", "host-gateway")
                .withAccessToHost(true)
                .withNetwork(NETWORK);
        ACTIVE_MQ_CONTAINER.start();
    }

    static {
        boolean started = false;
        while (!started) {
            try {
                log.info("ACTIVE_MQ_CONTAINER.getFirstMappedPort(): " + ACTIVE_MQ_CONTAINER.getMappedPort(5672));
                started = true;
            } catch (Exception e) {
                // nothing
                log.info("in loop error");
            }
        }
    }

alternative is:

 private static final GenericContainer<?> FIRST_CONTAINER = new GenericContainer<>(
        JUnitJupiterTestImages.HTTPD_IMAGE).withExposedPorts(80);

    private static final GenericContainer<?> SECOND_CONTAINER = new GenericContainer<>(
        JUnitJupiterTestImages.HTTPD_IMAGE).withExposedPorts(80);

    private static final GenericContainer<?> APP_CONTAINER = new GenericContainer<>(JUnitJupiterTestImages.HTTPD_IMAGE)
        .dependsOn(FIRST_CONTAINER, SECOND_CONTAINER).withExposedPorts(80);

    @BeforeAll
    public static void setupWithException() {
                FIRST_CONTAINER.start();
                SECOND_CONTAINER.start();
                // read mapped ports after containers are started
                APP_CONTAINER
                     .withEnv(FIRST_DEPENDENCY_ENV_KEY, String.valueOf(FIRST_CONTAINER.getFirstMappedPort()))
                     .withEnv(SECOND_DEPENDENCY_ENV_KEY, String.valueOf(SECOND_CONTAINER.getFirstMappedPort()));

                APP_CONTAINER.start();

Expected behavior should be:

    @Container
    public static final GenericContainer<?> ACTIVE_MQ_CONTAINER = new GenericContainer<>(ACTIVE_MQ_IMAGE)
            .withExposedPorts(61616, 8161, 5672);
            
            
    @Container
    private static final GenericContainer<?> MOCK_SERVER = new GenericContainer<>(MOCK_SERVER_IMAGE)
            .withExposedPorts(1080);
            
    @Container
    private static final GenericContainer MS_SQL_CONTAINER = new GenericContainer<>(MS_SQL_IMAGE)
            .withEnv("ACCEPT_EULA", "Y")
            .withEnv("SA_PASSWORD", "yourStrong(!)Password")
            .withNetwork(NETWORK)
            .withExposedPorts(1433);

    @Container
    private static final GenericContainer<?> APP_SERVER = new GenericContainer<>(APP_IMAGE)
            .dependsOn(MS_SQL_CONTAINER,MOCK_SERVER, ACTIVE_MQ_CONTAINER)
            .withEnv("ConnectionStrings__AzureServiceBus", () -> "amqp://host.docker.internal:" + ACTIVE_MQ_CONTAINER.getMappedPort(5672))
...

Last line:
.withEnv("ConnectionStrings__AzureServiceBus", "amqp://host.docker.internal:" + ACTIVE_MQ_CONTAINER.getMappedPort(5672))
replaced by deferred value retrieval:
.withEnv("ConnectionStrings__AzureServiceBus", () -> "amqp://host.docker.internal:" + ACTIVE_MQ_CONTAINER.getMappedPort(5672))

ensures proper startup order when one container depends on some runtime value of another container.

Beginne mit GenericContainer.withEnv und dem im Issue beschriebenen @Container-Start- und Abhängigkeitspfad. Verfolge, wann Umgebungswerte relativ zu dependsOn und der Verfügbarkeit zugeordneter Ports gelesen werden. Als erledigt gilt die Aufgabe, wenn ein auf Supplier basierender Umgebungswert während des Starts des abhängigen Containers aufgelöst wird, sodass das gezeigte Beispiel ohne manuelle Starts funktioniert.