Set kafka client service name to application default service name.

[mar-kolya]

So that spans inheriting from that client span have application
service name rather than 'kafka'

[labbati]

LGTM! Just a thought though.

Assume that we have an app that only have a consumer and does not have a producer.

Wouldn't we loose visibility on the fact that such app depends on service Kafka? I may be missing something big here and what I wrote might make no sense.

While I do not object that the work done on the consumer callback can be considered part of the application service and not the kafka service, shouldn't we at least instrument the consumer constructor to keep track of the fact that we are at least depending on an external service? Unless I am missing this part from the code, we are not currently doing it.

[labbati]

I wrongly approved it. Please see the comment above.

[mar-kolya]

So in my humble opinion:

• Kafka consumer span still has 'kafka' in some of its fields - so it is fairly obvious that it is coming from kafka when one looks at the span itself.
• Delay in kafka consumer (or any queue consumer, for that matter) is usually not important - we do not care how long we wait for messages, we care long it takes to process them - so we mainly need consumer span to start off processing trace.
• I think services would still be linked assuming producer has APM integration. If producer doesn't have an APM integration I would feel not much changes either.

I would agree that this may not be an ideal solution and it would be nice to have some way to change service name for children spans while not touching parent span - but so far I do not see a good way to do that,

[labbati]

I see the point and for me this is ok to merge.

My comment above was referred also to the fact that in the service map (as an example) you would not even see an arrow from application to a service named kafka. But this may be secondary.
So I stand by my approval then 😄