Hi all The PR https://github.com/apache/pulsar/pull/21155 fixes an issue in which the producer sends messages timeout due to the inability to reconnect successfully. The root cause is the client created a new connection to reregister the producer after it assumed the old client was invalidated, but at the same time, the broker assumed the old connection was still validated, so the client got an error "Producer with name 'st-0-5' is already connected to topic".
The fix in the PR https://github.com/apache/pulsar/pull/21155 tries to start a new heartbeat after the broker receives different connections for the same producer registration. In this fix, the PR https://github.com/apache/pulsar/pull/21155 uses a tool method `Servercnx.checkConnectionLiveness`( introduced in the PR https://github.com/apache/pulsar/pull/20026). I want to cherry-pick the tool method `Servercnx.checkConnectionLiveness` into branch-2.10 and branch-2.11 along with the PR #21155 Thanks Yubiao Feng
