[#4569][pulsar-client] C++ client producer sendAsync() method will be blocked forever, if enough batched messages sent timeout. (#4569)

[easyfan]

Fixes #4569

Motivation

*Root cause: a simple mistake in pulsar/pulsar-client-cpp/lib/ProducerImpl.cc:

The reserved spots for all individual messages in a batch message (just reserved, not occupied by pushing in) did not be released in the case of batching message sent failure (sent timeout or any other failure cases), which was processed by ProducerImpl::failPendingMessages(...)*

Modifications

When dealing any failure message, if the current message is a batch one, we should also release the reserved spots in the pendingMessageQueue_, for all individual messages inside this batch message.

Verifying this change

• Make sure that the change passes the CI checks.

This change is already covered by existing tests, such as pulsar/pulsar-client-cpp/tests/ProducerTest.cc.

• Dependencies (does it add or upgrade a dependency): (no)
• The public API: (no)
• The schema: (no)
• The default values of configurations: (no)
• The wire protocol: (no)
• The rest endpoints: (no)
• The admin cli options: (no)
• Anything that affects deployment: no)

Documentation

• Does this pull request introduce a new feature? (no)

[merlimat]

Nice catch on this one!

I think this originates from the fact that pendingMessagesQueue_.clear() does not indeed reset the reserver spots counter

[merlimat]

run cpp tests

[merlimat]

run cpp tests

[easyfan]

@merlimat Already merged? So what happened to the CI blocker?

[merlimat]

Master branch was fixed yesterday. When CI runs, it attempts to do a clean merge with master, so the fix was automatically picked up just by retesting.