[Bug]: SimpleSpanProcessor might fail and error is ignored

[dotansimha]

What happened?

The SimpleSpanProcessor might fail silently on some runtime, for example, when thread::Builder::new() is called:

https://github.com/open-telemetry/opentelemetry-rust/blob/main/opentelemetry-sdk/src/trace/span_processor.rs#L106-L109

The error is ignored, and when Spans are reported, the self.message_sender.send call fails with a SendError (internally, the error is Disconnected).

I was trying to run this on a wasm32-unknown-unknown runtime, and it failed silently. Using the global error handler, I was able to get the Disconnected error, and then I figured out that it happens where there are not subscribers listening.

The

API Version

0.x

SDK Version

opentelemetry_sdk@0.21.2

What Exporters are you seeing the problem on?

N/A

Relevant log output

failed to spawn exporter thread: Error { kind: Unsupported, message: "operation not supported on
  this platform" }

[cijothomas]

Would switching SimpleSpanProcessor to be similar to SimpleLogRecordProcessor be sufficient?

This was discussed here : #1409

[TommyCpp]

I think particulate case is caused by we cannot create new thread in WASM as we did for tranditional platform. Switching to mutex based simple span processor. We can look into improving this when we start supporting wasm