Jason Gustafson created KAFKA-13417:
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Summary: Dynamic thread pool re-configurations may not get
processed
Key: KAFKA-13417
URL: https://issues.apache.org/jira/browse/KAFKA-13417
Project: Kafka
Issue Type: Bug
Reporter: Jason Gustafson
Assignee: Jason Gustafson
`DynamicBrokerConfig.updateCurrentConfig` includes the following logic to
update the current configuration and to let each `Reconfigurable` process the
update:
{code}
val oldConfig = currentConfig
val (newConfig, brokerReconfigurablesToUpdate) =
processReconfiguration(newProps, validateOnly = false)
if (newConfig ne currentConfig) {
currentConfig = newConfig
kafkaConfig.updateCurrentConfig(newConfig)
// Process BrokerReconfigurable updates after current config is updated
brokerReconfigurablesToUpdate.foreach(_.reconfigure(oldConfig, newConfig))
}
{code}
The problem here is that `currentConfig` gets initialized as `kafkaConfig`
which means that the first call to `kafkaConfig.updateCurrentConfig(newConfig)`
ends up mutating `currentConfig` and consequently `oldConfig`. The problem with
this is that some of the `reconfigure` implementations will only apply a new
configuration if the value in `oldConfig` does not match the value in
`newConfig`. For example, here is the logic to update thread pools dynamically:
{code}
override def reconfigure(oldConfig: KafkaConfig, newConfig: KafkaConfig):
Unit = {
if (newConfig.numIoThreads != oldConfig.numIoThreads)
server.dataPlaneRequestHandlerPool.resizeThreadPool(newConfig.numIoThreads)
if (newConfig.numNetworkThreads != oldConfig.numNetworkThreads)
server.socketServer.resizeThreadPool(oldConfig.numNetworkThreads,
newConfig.numNetworkThreads)
if (newConfig.numReplicaFetchers != oldConfig.numReplicaFetchers)
server.replicaManager.replicaFetcherManager.resizeThreadPool(newConfig.numReplicaFetchers)
if (newConfig.numRecoveryThreadsPerDataDir !=
oldConfig.numRecoveryThreadsPerDataDir)
server.logManager.resizeRecoveryThreadPool(newConfig.numRecoveryThreadsPerDataDir)
if (newConfig.backgroundThreads != oldConfig.backgroundThreads)
server.kafkaScheduler.resizeThreadPool(newConfig.backgroundThreads)
}
{code}
Because of this, the dynamic update will not get applied the first time it is
made. I believe subsequent updates would work correctly though because we would
have lost the indirect reference to `kafkaConfig`. Other than the
`DynamicThreadPool` configurations, it looks like the config to update unclean
leader election may also be affected by this bug.
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