Add opentelemetry to manually created gRPC channel

[LarsSven]

We have the requirement that we need to be able to send gRPC requests to arbitrary hosts (the hostname/port to send the message to are part of the user request essentially). Since Quarkus only supports pointing gRPC clients towards static hosts, we have the following bit of code:

suspend fun runAction(endpoint: RuntimeEndpoint, request: RunActionRequest): RunActionResponse {
    val channel = ManagedChannelBuilder.forAddress(
        endpoint.host,
        endpoint.port,
    ).usePlaintext().build()

    val stub = ActionServiceGrpc.newBlockingStub(channel)

    return try {
        withTimeout(request.limits.wallTime * 60) {
            stub.runAction(request)
        }
    } finally {
        channel.shutdown()
    }
}

However we would really like to add otel tracing to this like the managed gRPC clients by Quarkus have. I have tried to look through the documentation and the code, but found it all a bit much and hard to grasp. Would you perhaps have any pointers for how I can integrate this with the Quarkus otel tracing like the Quarkus managed gRPC clients have?

[quarkus-bot[bot]]

/cc @alesj (grpc), @brunobat (opentelemetry), @cescoffier (grpc), @geoand (kotlin), @radcortez (opentelemetry)

[LarsSven]

Actually I managed to solve it!

For anyone else who is trying to do a similar thing, it's as simple as:

@ApplicationScoped
class ActionRunner {
    @Inject
    private lateinit var otelTracingInterceptor: GrpcTracingClientInterceptor

    /**
     * Runs an action on a runtime.
     *
     * @param endpoint The endpoint to send the action gRPC request to.
     * @param request The request to run against the runtime.
     *
     * @return The response from the runtime.
     */
    suspend fun runAction(endpoint: RuntimeEndpoint, request: RunActionRequest): RunActionResponse {
        val channel = Grpc
            .newChannelBuilderForAddress(endpoint.host, endpoint.port, InsecureChannelCredentials.create())
            .build()

        val stub = ActionServiceGrpc.newBlockingStub(channel).withInterceptors(
            otelTracingInterceptor
        )

        return try {
            withTimeout(request.limits.wallTime * 60) {
                stub.runAction(request)
            }
        } finally {
            channel.shutdown()
        }
    }
}

You just inject Quarkus' GrpcTracingClientInterceptor and then add it to the stub.