[KAFKA-10063] UnsupportedOperation when querying cleaner metrics after shutdown

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.6.0
• Assignee: Chia-Ping Tsai
• Reporter: Jason Gustafson
• Created: 28/May/20 21:27
• Updated: 09/Jun/20 16:31
• Resolved: 08/Jun/20 23:47

Description

We have a few log cleaner metrics which iterate the set of cleaners. For example:

  newGauge("max-clean-time-secs", () => cleaners.iterator.map(_.lastStats.elapsedSecs).max.toInt)

It seems possible currently for LogCleaner metrics to get queried after shutdown of the log cleaner, which clears the `cleaners` collection. This can lead to the following error:

java.lang.UnsupportedOperationException: empty.max
	at scala.collection.IterableOnceOps.max(IterableOnce.scala:952)
	at scala.collection.IterableOnceOps.max$(IterableOnce.scala:950)
	at scala.collection.AbstractIterator.max(Iterator.scala:1279)
	at kafka.log.LogCleaner.kafka$log$LogCleaner$$$anonfun$new$9(LogCleaner.scala:132)
	at kafka.log.LogCleaner$$anonfun$4.value(LogCleaner.scala:132)
	at kafka.log.LogCleaner$$anonfun$4.value(LogCleaner.scala:132)

Issue Links

• links to: GitHub Pull Request #8783