LogBackend logs from different fiber

[caspiano]

Describe the bug

The OpenTelemetry::Instrumentation::LogBackend logs asynchronously from a different fiber.
This prevents the logs from being attached to the span from which the log entry was produced.

To Reproduce

Configure the Log with OpenTelemetry::Instrumentation::LogBackend as the log backend.

Expected behavior

Logs emitted to OpenTelemetry::Instrumentation::LogBackend should be attached as events to the span that produced the Log::Entry

[wyhaines]

Ah. This makes sense. The solution will take a little more thought, though.

[wyhaines]

I think the easiest fix here is to make the OpenTelemetry::Instrumentation::LogBackend only operate with a SyncDispatcher. The only thing that it is doing is adding an event to the existing span, so this should be extremely fast, which reduces any argument for an AsyncDispatcher. Also, if using the AsyncDispatcher, the code would have to ensure that the Span object itself still exists by the time that the LogBackend#write method ends up being called.

[caspiano]

Nice! That seems like the most logical solution