Producer#flush doesn't respect non-batched messages

[equanz]

Search before asking

• I searched in the issues and found nothing similar.

Version

main( ba1a7e1 )

Minimal reproduce step

1. Create a producer with batchingEnabled=false
2. Send some messages asynchronously
3. Call Producer#flush or Producer#flushAsync
4. (Close a producer)

• to get AlreadyClosed exception
  

  pulsar-client-cpp/lib/ProducerImpl.cc

  Lines 665 to 666 in ba1a7e1

  	// ensure any remaining send callbacks are called before calling the close callback
  	failPendingMessages(ResultAlreadyClosed, false);

What did you expect to see?

When Producer#flush or Producer#flushAsync is called, wait for the completion of sending messages, even if non-batched messages.

What did you see instead?

Producer#flush and Producer#flushAsync don't guarantee the completion of sending non-batched messages.

Anything else?

Currently, ProducerImpl#flushAsync do nothing if batchMessageContainer_ is not initialized.

pulsar-client-cpp/lib/ProducerImpl.cc

Lines 331 to 333 in ba1a7e1

	} else {
	callback(ResultOk);
	}

In Java client, wait last sent messages. We should implement C++ client like it.
apache/pulsar#2103

Are you willing to submit a PR?

• I'm willing to submit a PR!

[shibd]

I reproduced it and I'll start fixing it.

[equanz]

I'll close this issue because #98 was merged.
Thank you @shibd.