Tracing not propagated across @Async

[dansiviter]

Expected Behavior

When using @Aync methods the TraceContext is automatically propagated to the new thread linking in with instigating trace. Similar to io.opentelemetry.context.Context#wrap(...).

Actual Behaviour

When @Async is used instigating TraceContext is ignored leaving holes in the resulting trace. The issue goes away if @Async is removed, but that defeats the point.

Steps To Reproduce

1. Annotate a methods with @Async,
2. Invoke the method with a call that has a TraceContext (i.e. HTTP request with B3 header).

Environment Information

• OS: N/A
• Micronaut Trace: 4.1.1

Example Application

No response

Version

3.5.3

[graemerocher]

@n0tl3ss please take a look

[n0tl3ss]

Hi @dansiviter, I tried to recreate test example without success. Could you please provide me Controller class where issue exists. Thanks

[dansiviter]

@n0tl3ss I can't share the code, so will have to create an example when I find some time.

[dansiviter]

After a lot of debugging, I believe the issue can be fixed by tracing.instrument-threads: true (see micronaut-projects/micronaut-core#2307).

Can this behaviour be documented please as it is confusing.

[graemerocher]

If you provide an example maybe we can take it forward. Using instrument-threads can be unsafe if you use a lot of reactive code, hence it is disabled.

[dansiviter]

@graemerocher Every time you use @Async or use ExecutorService directly. All that is needed is a note in the tracing documentation that tracing will not propegate across ExecutorService unless that flag is enabled.

[dansiviter]

FYI, I've noticed that flag doesn't work for OpenTelemetry as there is no OTel equivalent for ThreadTracingInvocationInstrumentFactory.

[n0tl3ss]

We can add ThreadTracingInvocationInstrumentFactory for OTel if it is needed.