AWS IoT Device SDK for Java v2: problems following tutorial on Publish/subscribe local messages

[marcellorinaldo]

Hello!

I'm following the guide described in https://docs.aws.amazon.com/greengrass/v2/developerguide/ipc-publish-subscribe.html.

I've created a Greengrass component with the following Java code:

// credentials ipcServerSocketPath and authToken are read correctly from env variables
GreengrassCoreIPCClientV2 greengrassClient = GreengrassCoreIPCClientV2.builder()
                        .withSocketPath(ipcServerSocketPath)
                        .withAuthToken(authToken)
                        .withSocketDomain(SocketOptions.SocketDomain.LOCAL)
                        .build();

String topic = "test";
byte[] payloadBody = new String("hello").getBytes();

MessageContext messageContext = new MessageContext().withTopic(topic);
BinaryMessage binaryMessage = new BinaryMessage().withMessage(payloadBody).withContext(messageContext);
PublishMessage publishMessage = new PublishMessage().withBinaryMessage(binaryMessage);
PublishToTopicRequest publishToTopicRequest = new PublishToTopicRequest().withTopic(topic).withPublishMessage(publishMessage);

greengrassClient.publishToTopic(publishToTopicRequest);

Whenever i publish the message I got the following stacktrace:

software.amazon.awssdk.aws.greengrass.model.ServiceError
               	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
               	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:77)
               	at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
               	at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:499)
               	at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:480)
               	at com.google.gson.internal.ConstructorConstructor$4.construct(ConstructorConstructor.java:140)
               	at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:211)
               	at software.amazon.awssdk.eventstreamrpc.EventStreamRPCServiceModel$EventStreamPostFromJsonTypeAdapter.read(EventStreamRPCServiceModel.java:105)
               	at software.amazon.awssdk.eventstreamrpc.EventStreamRPCServiceModel$EventStreamPostFromJsonTypeAdapter.read(EventStreamRPCServiceModel.java:79)
               	at com.google.gson.Gson.fromJson(Gson.java:991)
               	at com.google.gson.Gson.fromJson(Gson.java:956)
               	at com.google.gson.Gson.fromJson(Gson.java:905)
               	at com.google.gson.Gson.fromJson(Gson.java:876)
               	at software.amazon.awssdk.eventstreamrpc.EventStreamRPCServiceModel.fromJson(EventStreamRPCServiceModel.java:357)
               	at software.amazon.awssdk.eventstreamrpc.EventStreamRPCClient$1.onContinuationMessage(EventStreamRPCClient.java:102)
               	at software.amazon.awssdk.crt.eventstream.ClientConnectionContinuationHandler.onContinuationMessageShim(ClientConnectionContinuationHandler.java:41)

It does not seem a permission/authorization error.

Am I missing something?

aws-iot-device-sdk version 1.16.0
Greengrass CLI Version: 2.11.2

[yasminetalby]

Hello @marcellorinaldo ,
I am transferring this discussion to the AWS IoT Java SDK V2 repository for investigation.

Best,

Yasmine

[MikeDombo]

Please use the default builder for the client, you should not set any of those options yourself. GreengrassCoreIPCClientV2.builder().build().

You're using MessageContext which is only used when receiving messages, not when sending messages. The documentation notes "AWS IoT Greengrass Core software sets this context object in messages when you subscribe, and ignores this context object in messages that you publish."

You need to specify the topic to send to in the publish request, not in the message context.

Fully worked examples are provided in the documentation: https://docs.aws.amazon.com/greengrass/v2/developerguide/ipc-publish-subscribe.html#ipc-operation-publishtotopic:~:text=in%20its%20response.-,Examples,-The%20following%20examples

[MikeDombo]

And using that exact code gives you the error in greengrass.log? Please run it again.

The error says that the PublishToTopicRequest had no PublishMessage which does not match the code you have here.

In either the publisher or Greengrass log (look at systemd log output) do you see Illegal reflective access

[marcellorinaldo]

In either the publisher or Greengrass log (look at systemd log output) do you see Illegal reflective access

No, such error is not present anywhere.

[MikeDombo]

Did you retry running the code? Please show the full log.

[marcellorinaldo]

I figured out the problem (my side).

We are using an OSGi framework to integrate the publishing component into a larger application. After some debugging I found that the problem was an incomplete dependency com.google.gson on the classpath with the missing com.google.gson.annotations packages which was causing the error descibed above. Missing packages are usually found at runtime with a NoClassDefFound error. The absence of it mislead me to think that the problem was something else related to the way I used Greengrass.

Thanks for the kind support, from my side you can close the issue.

[MikeDombo]

Alright then, I'm glad you were able to figure it out.

[github-actions[bot]]

Hello! Reopening this discussion to make it searchable.