Otel threads spawn before "main" impact signal handling

[nleclercq]

Its seems that otel-ccp spawn some threads even before the main function is executed.
That's at least true when the instrumented application is linked against when the otlp_grpc_exporter.
Placing a breakpoint at the entry of main, we clearly see that 3 gRPC threads are already there. I guess they are spawn by hook executed when the shared library is loaded.

The problem is that this behavior as an impact on the signal handling mechanism implemented by our (shared) library. It, in fact, prevents our handler from behind called.

[lalitb]

@nleclercq - Can you share the stack trace, to understand the origin of threads. Also if you have the self-contained reproduction. otlp_grpc_exporter doesn't spawn any threads as of now (until #2407 is merged). Batch span processor creates a worked thread during initialization, but it won't be before main unless you are creating a static/global instance of the processor. But all theory for now, will wait for more details from your side :)

[nleclercq]

Damned! I actually have a singleton statically initialized as a global variable which makes a call to opentelemetry::exporter::otlp::OtlpGrpcExporterFactory::Create. I should have identified it as a potential source of the problem - sorry. Thanks for pointing this out. I'm going to switch to an explicit instantiation and see if it solves the problem. Stay tuned.

[nleclercq]

Ok. Switching to an explicit instantiation solves the problem. Thanks. I think we can close this issue.

[owent]

@nleclercq - Can you share the stack trace, to understand the origin of threads. Also if you have the self-contained reproduction. otlp_grpc_exporter doesn't spawn any threads as of now (until #2407 is merged). Batch span processor creates a worked thread during initialization, but it won't be before main unless you are creating a static/global instance of the processor. But all theory for now, will wait for more details from your side :)

#2407 do not spawn any thread, it will reuse the background threads of gRPC, and they are also created during or after initialization.