BatchSpanProcessor.forceFlush() doesn't appear to flush anything

[kenfinnigan]

I was looking at shutdown hooks and following the code and I happened to notice that https://github.com/open-telemetry/opentelemetry-java/blob/main/sdk/trace/src/main/java/io/opentelemetry/sdk/trace/export/BatchSpanProcessor.java#L247 doesn't appear to actually flush any spans that might be present.

Am I missing where it happens or is it a bug?

[jkwatson]

This looks like a bug, for sure. Needs to flush the exporter when called, and use that as the result code.

[jkwatson]

I take it back... there's actually some subtlety in this implementation. The worker thread checks for a request for flushing every 100ms and will initiate the flush. So forceFlush() just sets this value and the worker thread picks it up and uses it. I think not a bug, actually. The code does need a comment about this, though! I will put in a PR to add it.

[jkwatson]

#2807

[kenfinnigan]

Thanks!