Use ProducerContext as active context in Consumer

[Steffen911]

Summary

I would like to request a feature flag that toggles whether the ProducerContext should be reused as the ConsumerContext, i.e. Producer and Consumer would be within the same trace.

Current behaviour

We currently observe that the consumer is linked to the producer, but in our APM tools (Datadog, Jaeger) spans aren't shown in the same burn chart. In our case, it would be desirable to use the same TraceId for Consumer and Producer.

Expected behaviour

Add a feature flag to use the Producer Context as active context when creating the consumer span. My assumption is that this would be an update in https://github.com/appsignal/opentelemetry-instrumentation-bullmq/blob/main/src/instrumentation.ts#L449 to use producerContext instead of currentContext. As this would be a breaking behaviour in certain scenarios, I would toggle that flag to false by default.

[Steffen911]

@unflxw Would you have any concerns about this proposal? I'm happy to start a pull request if this has a chance of getting merged.

[unflxw]

Hi @Steffen911, thanks for the suggestion!

I am okay with this being implemented with a false-by-default configuration flag, as this is a common behaviour in other OpenTelemetry background job instrumentations. Please feel free to send a PR our way.

Do note, however, that the OpenTelemetry Semantic Conventions for Messaging Spans say that links should be used:

A single “Process” or “Receive” span can account for a single message, for a batch of messages, or for no message at all (if it is signalled that no messages were received). For each message it accounts for, the “Process” or “Receive” span SHOULD link to the message’s creation context.

I think the reason for this is to support batch message processing. BullMQ Pro does have batch message processing functionality, but this instrumentation currently does not support it. With batch message processing, the same process spans would need to have multiple parents. Anyway, this is not an issue at the moment.

Finally, do note that it is possible to see span links in Datadog, though not as part of the same trace.

My assumption is that this would be an update in https://github.com/appsignal/opentelemetry-instrumentation-bullmq/blob/main/src/instrumentation.ts#L449 to use producerContext instead of currentContext.

Yes, and to not create a link using producerContext here: https://github.com/appsignal/opentelemetry-instrumentation-bullmq/blob/main/src/instrumentation.ts#L479-L482

(If they're parent-child, I don't think they should also be linked)

[Steffen911]

Thank you for the feedback! I created #11 which should cover this requirement.

[Steffen911]

@unflxw Thank you for your support here! Could you also do a new release which includes this change?

[unflxw]

@Steffen911 Done! @appsignal/[email protected] has been released. Thank you for your contribution!

Do note that I renamed the config option in #12.

[Steffen911]

Thank you 🙏