jaro-herod opened a new issue, #25837: URL: https://github.com/apache/pulsar/issues/25837
### 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 Java Client Library : ┌─────────┬───────────────────────────┐ │ Version │ Bug present? │ ├─────────┼───────────────────────────┤ │ 4.1.1 │ ✅ yes │ ├─────────┼───────────────────────────┤ │ 4.1.2 │ ✅ yes │ ├─────────┼───────────────────────────┤ │ 4.1.3 │ ✅ yes │ ├─────────┼───────────────────────────┤ │ 4.2.0 │ ✅ yes │ ├─────────┼───────────────────────────┤ │ 4.2.1 │ ✅ yes │ ├─────────┼───────────────────────────┤ │ master │ ✅ yes (as of 2026-05-20) │ └─────────┴───────────────────────────┘ ### Issue Description Calling consumer.hasMessageAvailable() (or the async variant) on a consumer created via PulsarClient.newConsumer().subscribe() throws UnsupportedOperationException: Unknown MessageId type: null if called before any message has been dequeued. The exception propagates from MessageIdAdv.compareTo() when ConsumerImpl.hasMoreMessages() is called with a null startMessageId. ### Error messages ```text java.lang.UnsupportedOperationException: Unknown MessageId type: null at org.apache.pulsar.client.api.MessageIdAdv.compareTo(MessageIdAdv.java:106) at org.apache.pulsar.client.api.MessageIdAdv.compareTo(MessageIdAdv.java:29) at org.apache.pulsar.client.impl.ConsumerImpl.hasMoreMessages(ConsumerImpl.java:2805) at org.apache.pulsar.client.impl.ConsumerImpl.hasMessageAvailableAsync(ConsumerImpl.java:2757) at org.apache.pulsar.client.impl.ConsumerImpl.hasMessageAvailable(ConsumerImpl.java:2694) ``` ### Reproducing the issue ``` PulsarClient client = PulsarClient.builder().serviceUrl("pulsar://localhost:6650").build(); Consumer<byte[]> consumer = client.newConsumer() .topic("persistent://my-tenant/my-ns/my-topic") .subscriptionName("my-sub") .subscriptionType(SubscriptionType.Exclusive) .subscribe(); // Throws UnsupportedOperationException BEFORE any readNext() call: boolean hasMessages = consumer.hasMessageAvailable(); ``` Note: The exception does not occur if consumer.receive() / consumer.receive(timeout, unit) is called at least once first, because lastDequeuedMessageId is then non-earliest and hasMoreMessages takes a different code path. ### Additional information _No response_ ### Are you willing to submit a PR? - [ ] 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]
