Span are not exported by the BatchSpanProcessor

[jderusse]

Describe your environment

Since #788 spans are not all flushed.

• in the onEnd methods, spans are pushed to the batch array buffer.
• the batch buffer is moved to the queue stack by the enqueueBatch method
• the enqueueBatch is called:
  • when the batch buffer has more than maxExportBatchSize traces
  • Or when shouldFlush return true and queue is empty => this requires autoFlush + $this->clock->now() > $this->nextScheduledRun

There are cases (less span than maxExportBatchSize and process finish in less than scheduledDelayNanos) Where spans are not moved from batch buffer to queue stack and thus not flushed / exported

possible solution

Adds if ($this->batch !== []) { $this->enqueueBatch();} in shutdown and forceFlush and ask people to call these methods (or call shutdown on __destruct)

[bobstrecansky]

@Nevay - wanted to check with you that you approve of this approach before we implemented it.

[Nevay]

Calling ::shutdown() is necessary and should flush all enqueued spans (::shutdown() adds the current batch id to the $this->flush queue); do you have a reproducer that calls ::shutdown()?

It's important to run the tracer provider's shutdown() method when the PHP process ends, to enable flushing of any enqueued telemetry.

[jderusse]

indeed, calling shutdown fixes the issue. Sorry for the noise