OpenTracing with Kafka Streams - How to?

zooes :

I am trying to integrate Jaeger tracing into K-Streams. I was planning to add tracing to few of my most important pipelines and was wondering what would be a good way to pass traceid from one piepline to another?

Here is what I have so far - At the start of stream processing pipeline, I start a server span and save the traceid into a state store. Later on, in a transform pipeline, I access the statestore and capture the trace from the transform() method. Is this a good way to handle tracing in stream processing?

input
  .mapValues(toSomethingThatMyAppUnderstands)      
  .mapValues(this::startStreamTrace)
  .filter((k, v) -> v.isPresent())            
  .mapValues(Optional::get)                   
  .mapValues(doSomethingHereWith)       
  .flatMapValues(doSomethingElse)       
  .filter((k, v) -> isInterestingEvent(v))    
  .transform(() -> new TransformerWithTracing<SomeObjectA, SomeObjectB>(IN_MEM_STORE_NAME, someFunction), IN_MEM_STORE_NAME)
  .flatMapValues(c -> c)
  .to(outTopic, Produced.with(Serdes.String(), new EventSerde()));



public class TransformerWithTracing<V, VR> implements Transformer<String, V, KeyValue<String, VR>> {

  final Function valueAction;
  final String storeId;
  private KeyValueStore<String, String> traceIdStore;

  public TransformerWithTracing(String storeId, Function valueAction) {
    this.storeId = storeId;
    this.valueAction = valueAction;
  }

  @Override
  public void init(ProcessorContext context) {
   // KeyValueStore store = ((KeyValueStore<String, String>) context.getStateStore(storeId));
    InMemoryKeyValueStore inMemoryKeyValueStore = (InMemoryKeyValueStore) store;
    this.traceIdStore = store;
  }

  @Override
  public KeyValue<String, VR> transform(String key, V value) {
    System.out.println(traceIdStore.get(key));

    // BuildTraceHeader 
    try(Scope scope = serviceTracer.startServerSpan(traceHeader, "Converting to Enterprise Event")) {
      return KeyValue.pair(key, (VR) valueAction.apply(value));
    }
  }

  @Override
  public KeyValue<String, VR> punctuate(long timestamp) {
    return null;
  }

  @Override
  public void close() {
//    if (streamId != null)   traceIdStore.delete(streamId);
  }

}

lenny :

There are similar ideas in this zipkin/brave repo by @jeqo.

https://github.com/jeqo/brave/tree/kafka-streams-processor/instrumentation/kafka-streams

There also seems to be something available in opentracing-contrib repo but it seems to only at trace producer/consumer level.

https://github.com/opentracing-contrib/java-kafka-client/tree/master/opentracing-kafka-streams

• lenny