[CASSANDRA-8862] Commit log pending tasks incremented during getPendingTasks

• Type: Bug
• Status: Resolved
• Priority: Low
• Resolution: Fixed
• Fix Version/s: 2.1.5
• Severity: Low
• Assignee: Jonathan Ellis
• Reporter: Michael Swiecicki

Authors

Jonathan Ellis

• Created: 25/Feb/15 10:04
• Updated: 16/Apr/19 09:31
• Resolved: 26/Feb/15 05:24

Description

After upgrading from Cassandra 2.0.8 to 2.1.2 our monitoring based on JMX metrics shows increasing number of commit log pending tasks. From what we found out, this value is now incremented every time it is fetched.

It is easy to reproduce using tool like JConsole by refreshing value of PendingTasks attribute.

Quick look at the code shows that this behavior was probably introduced in 2.1 with CASSANDRA-3578 where getPendingTasks in AbstractCommitLogService was changed from returning queue.size() to returning pending.incrementAndGet(). As a result this counter is incremented when getting value of Commitlog.PendingTasks from org.apache.cassandra.db (now deprecated) or CommitLog.PendingTasks from org.apache.cassandra.metrics.

Could you please clarify if this is expected behavior?
This was already mentioned in CASSANDRA-8531.

Issue Links

• is related to: CASSANDRA-9339 Commit Log completed tasks incremented during getCompletedTasks
• relates to: CASSANDRA-9105 JMX APIs appear untested