There is at least one place where sendAsync does not release the semaphore

[scr-oath]

Describe the bug

If an error occurs that completes the future without releasing the semaphore then the calling thread may block forever.

https://github.com/apache/pulsar/blob/master/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ProducerImpl.java#L354

There may be another case with timeout that tickles this but that's harder to reproduce

To Reproduce
Steps to reproduce the behavior:

Send a bunch of large messages asynchronously; hang

Expected behavior
Any failure path should release the semaphore before returning.

Screenshots
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Desktop (please complete the following information):

• OS: [e.g. iOS]

Additional context
Add any other context about the problem here.

[jiazhai]

@scr-oath Would you like to provide a fix for this?

[jiazhai]

Thanks a lot for the reporting and analysis.

[sijie]

This is fixed by #6488

[scr-oath]

Thanks!

[scr-oath]

@scr-oath Would you like to provide a fix for this?

Looks like you got it!