rondagostino commented on a change in pull request #10008:
URL: https://github.com/apache/kafka/pull/10008#discussion_r569444234
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File path:
core/src/main/scala/kafka/coordinator/group/GroupMetadataManager.scala
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@@ -78,7 +78,20 @@ class GroupMetadataManager(brokerId: Int,
private val shuttingDown = new AtomicBoolean(false)
/* number of partitions for the consumer metadata topic */
- private val groupMetadataTopicPartitionCount =
getGroupMetadataTopicPartitionCount
+ private var _groupMetadataTopicPartitionCount: Option[Int] = Option.empty //
lazy, once-only evaluation
+ private def groupMetadataTopicPartitionCount: Int = {
+ _groupMetadataTopicPartitionCount match {
+ case Some(partitionCount) => partitionCount
+ case None => synchronized { // make sure we only invoke the function once
+ _groupMetadataTopicPartitionCount match {
+ case Some(partitionCount) => partitionCount // another thread beat
us to it
+ case None =>
+ _groupMetadataTopicPartitionCount =
Some(offsetsTopicPartitionCountFunc())
Review comment:
This is no longer an issue since we invoke the function once in
`startup()`. We do it again in `TransactionStateManager` whenever we become
leader for a partition, but that happens in the scheduler thread where any
exception will be caught/logged.
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