Dec 14, 2021
7 min read

What’s New in Apache Pulsar 2.7.4

Yu Liu

The Apache Pulsar community releases version 2.7.4! 32 contributors provided improvements and bug fixes that delivered 98 commits.

Highlights of this release are as below:

  • Upgrade Log4j to 2.17.0 - CVE-2021-45105. PR-13392
  • ManagedLedger can be referenced correctly when OpAddEntry is recycled. PR-12103
  • NPE does not occur on OpAddEntry while ManagedLedger is closing. PR-12364

This blog walks through the most noteworthy changes grouped by the affected functionalities. For the complete list including all enhancements and bug fixes, check out the Pulsar 2.7.4 Release Notes.

Notable bug fixes and enhancements

Upgrade Log4j to 2.17.0 - CVE-2021-45105. PR-13392

  • Issue
  • A serious vulnerability was reported regarding Log4j that can allow remote execution for attackers. The vulnerability issue is described and tracked under CVE-2021-44228.
  • Resolution
  • Pulsar 2.7.4 upgraded Log4j to 2.17.0.

ManagedLedger can be referenced correctly when OpAddEntry is recycled. PR-12103

  • Issue
  • Previously, after a write failure, a task was scheduled in the background to force close the ledger and trigger the creation of a new ledger. If the OpAddEntry instance was already recycled, that could lead to either an NPE or undefined behavior.
  • Resolution
  • The ManagedLedgerImpl object reference is copied to a final variable so the background task will not be dependent on the lifecycle of the OpAddEntry instance.

No potential race condition in the BlobStoreBackedReadHandler. PR-12123

  • Issue
  • Previously, BlobStoreBackedReadHandler entered an infinite loop when reading an offload ledger. There was a race condition between the operation of reading entries and closing BlobStoreBackedReadHandler.
  • Resolution
  • Added a state check before reading entries and made the BlobStoreBackedReadHandler exit loop when the entryID is bigger than the lastEntryID.

NPE does not occur on OpAddEntry while ManagedLedger is closing. PR-12364

  • Issue
  • Previously, the test ManagedLedgerBkTest#managedLedgerClosed closed ManagedLedger object on some asyncAddEntry operations and failed with NPE.
  • Resolution
  • Closed OpAddEntry when ManagedLedger signaled OpAddEntry to fail. In this way, the OpAddEntry object was correctly recycled and the failed callback was correctly triggered.

Set a topic policy through the topic name of a partition correctly. PR-11294

  • Issue
  • Previously, the topic name of a partition could not be used to set a topic policy.
  • Resolution
  • Allowed setting a topic policy through a topic name of a partition by converting the topic name of a partition in SystemTopicBasedTopicPoliciesService.

Dispatch rate limiter takes effect for consumers. PR-8611

  • Issue
  • Previously, dispatch rate limiter did not take effect in cases where all consumers started reading in the next second since acquiredPermits was reset to 0 every second.
  • Resolution
  • Changed the behaviour of DispatchRateLimiter by minus permits every second instead of reset acquiredPermits to 0. Consumers stopped reading entries temporarily until acquiredPermits returned to a value less than permits .

NPE does not occur when executing unload bundles operations. PR-11310

  • Issue
  • When performing pressure tests on persistent partitioned topics, NPE occurred when executing unload bundles operations. Concurrently, producers did not write messages.
  • Resolution
  • Added more safety checks to fix this issue.

Fix inconsistent behavior for Namespace bundles cache. PR-11346

  • Issue
  • Previously, namespace bundle cache was not invalidated after a namespace was deleted.
  • Resolution
  • Invalidated namespace policy cache when bundle cache was invalidated.

Close the replicator and replication client after a cluster is deleted. PR-11342

  • Issue
  • Previously, the replicator and the replication client were not closed after a cluster was deleted. The producer of the replicator would then try to reconnect to the deleted cluster continuously.
  • Resolution
  • Closed the relative replicator and replication client.

Publish rate limiter takes effect as expected. PR-10384

  • Issue
  • Previously, there were various issues if preciseTopicPublishRateLimiterEnable was set to true for rate limiting:
  • Updating the limits did not set a boundary when changing the limits from a bounded limit to an unbounded limit.
  • Each topic created a scheduler thread for each limiter instance.
  • Topics did not release the scheduler thread when the topic was unloaded or the operation closed.
  • Updating the limits did not close the scheduler thread related to the replaced limiter instance
  • Resolution
  • Cleaned up the previous limiter instances before creating new limiter instances.
  • Used brokerService.pulsar().getExecutor() as the scheduler for the rate limiter instances.
  • Added resource cleanup hooks for topic closing (unload).

Clean up newly created ledgers if fails to update ZNode list. PR-12015

  • Issue
  • When updating a ZNode list, ZooKeeper threw an exception and did not clean up the created ledger. Newly created ledgers were not indexed to a topic managedLedger list and could not be cleared up as topic retention. Also, ZNode numbers increased in ZooKeeper if the ZNode version mismatch exception was thrown out.
  • Resolution
  • Deleted the created ledger from broker cache and BookKeeper regardless of exception type when the ZNode list failed to update.

What’s Next?

If you are interested in learning more about Pulsar 2.7.4, you can download and try it out now!

Pulsar Summit Asia 2021 will take place on January 15-16, 2022. Register now and help us make it an even bigger success by spreading the word on social media!

For more information about the Apache Pulsar project and current progress, visit the Pulsar website, follow the project on Twitter @apache_pulsar, and join Pulsar Slack!

Get involved

To get started, you can download Pulsar directly or you can spin up a Pulsar cluster with a free 30-day trial of StreamNative Cloud! We also offer technical consulting and expert training to help get your organization started. As always, we are highly responsive to your feedback. Feel free to contact us if you have any questions at any time. We look forward to hearing from you and stay tuned for the next Pulsar release!

Yu Liu
Yu Liu is an Apache Pulsar PMC member and a content strategist from StreamNative.


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