[fix][client] Fix race-condition causing doReconsumeLater to hang when creating retryLetterProducer has failed

[hanmz]

Motivation

When retryLetterProducer creation fails, retryLetterProducer will be set to null. So retryLetterProducer==null may occur when race-condition is present, at this time, the results cannot be completed.

Only handle the situation when retryLetterProducer is not equal to null:

pulsar/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ConsumerImpl.java

Line 678 in 3f12269

if (retryLetterProducer != null) {

Modifications

When retryLetterProducer==null, mark the result as an completeExceptionally.

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

[lhotari]

Do you have a chance to add a test case?

[hanmz]

Do you have a chance to add a test case?

I've added a test case.

[lhotari]

LGTM, thanks for the contribution @hanmz