sandeep-mst opened a new issue, #25201: URL: https://github.com/apache/pulsar/issues/25201
### Search before reporting - [x] I searched in the [issues](https://github.com/apache/pulsar/issues) and found nothing similar. ### Read release policy - [x] I understand that [unsupported versions](https://pulsar.apache.org/contribute/release-policy/#supported-versions) don't get bug fixes. I will attempt to reproduce the issue on a supported version of Pulsar client and Pulsar broker. ### User environment - master ### Issue Description There is a reentrancy bug in the Pulsar producer send path where `pendingMessages.clear()` can be executed after a retry message has already been added to `pendingMessages`. This results in the retry send’s CompletableFuture never being completed. This can occur when a retry `sendAsync` is triggered synchronously from within a handleSync callback of a failed send, while holding the producer mutex. This happens in the [failPendingMessages](https://github.com/apache/pulsar/blob/master/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ProducerImpl.java#L2315) method which usually runs on the timer thread. As the [pendingMessages.clear()](https://github.com/apache/pulsar/blob/d630394cdd02792b2dbc3a55443637a5d593a137/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ProducerImpl.java#L2327) is after the completeExceptionally, the retry logic as the code below will add the retryMessage to pendingMessages first and then the clear is called. ``` CompletableFuture<MessageId> firstSend = producer.sendAsync(message); CompletableFuture<MessageId> retrySend = firstSend.handleAsync((msgId, ex) -> { assertNotNull(ex, "First send must timeout"); assertTrue(ex instanceof PulsarClientException.TimeoutException); return producer.sendAsync(retryMessage); }).thenCompose(f -> f); ``` ### Error messages ```text ``` ### Reproducing the issue Set a low timeout value and use synchronous retries as given in the above example. ### Additional information _No response_ ### Are you willing to submit a PR? - [x] I'm willing to submit a PR! -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
