Testcontainers: communication between containers

Question

I have 2 testcontainers, one which is a dynamodb instance, and the second one a spring-boot one that needs to connect with the first one. While running locally I was just connecting from spring-boot => dynamodb using localhost:8000 , which won't work given dynamic ports.

So I set up:

public static final GenericContainer dynamoDBLocal = new GenericContainer("amazon/dynamodb-local:latest")
            .withImagePullPolicy(PullPolicy.defaultPolicy())
            .withNetwork(network)
            .withNetworkAliases("dynoDBContainer")
            .withNetworkMode(network.getId())
            .withExposedPorts(8000);
public static final GenericContainer appContainer = new GenericContainer(APP_IMAGE_FUTURE)
            .withImagePullPolicy(PullPolicy.defaultPolicy())
            .withExposedPorts(8080)
            .withNetwork(network)
            .withNetworkAliases("appContainer")
            .withNetworkMode(network.getId())
            .waitingFor(Wait.forHttp("/login").forStatusCode(200))
            .dependsOn(dynamoDBLocal);

And in my @BeforeAll I pass in my dyno port to my appContainer using withEnv which correctly gets picked up.

However in my app container logs I still see: connection to localhost:something refused, while when from my local machine I try to connect to the dyno by keeping the container running using a breakpoint I can connect just fine using localhost:something ?

I saw an akin question, but there the answer seemingly no longer used dynamic ports which seemed to go a bit against the dynamic port aspect of testcontainers.

Answer 1

appContainer should have .withEnv("<dynamo-env-var>", "dynoDBContainer:8000")

When using containers in the same network there is no need to use the exposed random port.

You can find an example here