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Jun Rao commented on KAFKA-574: ------------------------------- Sure, Prashanth. Do you think that you can provide a patch in the next week or so? We start to looking into performance related issues and this one is on the critical path of leader elections. > KafkaController unnecessarily reads leaderAndIsr info from ZK > ------------------------------------------------------------- > > Key: KAFKA-574 > URL: https://issues.apache.org/jira/browse/KAFKA-574 > Project: Kafka > Issue Type: Bug > Components: core > Affects Versions: 0.8 > Reporter: Jun Rao > Priority: Blocker > Labels: bugs > Original Estimate: 48h > Remaining Estimate: 48h > > KafkaController calls updateLeaderAndIsrCache() in onBrokerFailure(). This is > unnecessary since in onBrokerFailure(), we will make leader and isr change > anyway so there is no need to first read that information from ZK. Latency is > critical in onBrokerFailure() since it determines how quickly a leader can be > made online. > Similarly, updateLeaderAndIsrCache() is called in onBrokerStartup() > unnecessarily. In this case, the controller does not change the leader or the > isr. It just needs to send the current leader and the isr info to the newly > started broker. We already cache leader in the controller. Isr in theory > could change any time by the leader. So, reading from ZK doesn't guarantee > that we can get the latest isr anyway. Instead, we just need to get the isr > last selected by the controller (which can be cached together with the leader > in the controller). If the leader epoc in a broker is at or larger than the > epoc in the leaderAndIsr request, the broker can just ignore it. Otherwise, > the leader and the isr selected by the controller should be used. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira