Inter container docker communication using network alias results in "Invalid DNS name"

Question

I sent a request to "container 1" from my localhost, which is supposed to call "container 2" in a synchronous fashion and return a response to the request made from the localhost. The request is received by container 1, but it fails to communicate with container 2.

PS: I am able to login to container 1 and ping container 2 ("ping metadata") using it's network alias without any issues.

• Container 1:

Dockerfile:

FROM java:8
WORKDIR /
ADD /target/api-1.0-jar-with-dependencies.jar api-1.0.jar
EXPOSE 8000 9000
CMD java -jar api-1.0.jar

Docker command:

docker run --network backend -d -p 8000:8000 api

Java code where exception is thrown:

String target = "metadata:9000";
ManagedChannel channel = ManagedChannelBuilder.forTarget(target)
                .usePlaintext()
                .build();
        MetadataGrpc.MetadataBlockingStub blockingStub = MetadataGrpc.newBlockingStub(channel);
        MetadataIO.Response response = blockingStub.create(req);
        responseObserver.onNext(response);
        responseObserver.onCompleted();
        shutdownManagedChannel(channel);

Exception:

Feb 04, 2021 11:33:50 PM io.grpc.internal.SerializingExecutor run
SEVERE: Exception while executing runnable io.grpc.internal.ServerImpl$JumpToApplicationThreadServerStreamListener$1HalfClosed@7fbc2a7f
java.lang.IllegalArgumentException: Invalid DNS name: linkview_domain_metadata:9000
    at com.google.common.base.Preconditions.checkArgument(Preconditions.java:217)
    at io.grpc.internal.DnsNameResolver.<init>(DnsNameResolver.java:171)
    at io.grpc.internal.DnsNameResolverProvider.newNameResolver(DnsNameResolverProvider.java:58)
    at io.grpc.internal.DnsNameResolverProvider.newNameResolver(DnsNameResolverProvider.java:41)
    at io.grpc.NameResolverRegistry$NameResolverFactory.newNameResolver(NameResolverRegistry.java:154)
    .......

• Container 2:

Dockerfile:

FROM java:8
WORKDIR /
ADD /target/metadata-1.0-jar-with-dependencies.jar metadata-1.0.jar
EXPOSE 9000
CMD java -jar metadata-1.0.jar

Docker command:

docker run --network-alias metadata --network backend -d  metadata

question from:https://stackoverflow.com/questions/66056127/inter-container-docker-communication-using-network-alias-results-in-invalid-dns

Answer 1

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