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https://issues.apache.org/jira/browse/KAFKA-3693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15279310#comment-15279310
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Jun Rao commented on KAFKA-3693:
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[~maysamyabandeh], yes, the logic in the controller is that when a broker is
started, the controller will include all partitions on this broker in the very
first LeaderAndIsrRequest to this broker. The high watermark checkpoint thread
is only started started after the first LeaderAndIsrRequest is received.
So, for the problem that you described, we will need to figure out why the
controller didn't include all partitions in the first LeaderAndIsrRequest. Is
the issue easily reproducible?
> Race condition between highwatermark-checkpoint thread and
> handleLeaderAndIsrRequest at broker start-up
> -------------------------------------------------------------------------------------------------------
>
> Key: KAFKA-3693
> URL: https://issues.apache.org/jira/browse/KAFKA-3693
> Project: Kafka
> Issue Type: Bug
> Components: core
> Affects Versions: 0.9.0.1
> Reporter: Maysam Yabandeh
>
> Upon broker start-up, a race between highwatermark-checkpoint thread to write
> replication-offset-checkpoint file and handleLeaderAndIsrRequest thread
> reading from it causes the highwatermark for some partitions to be reset to
> 0. In the good case, this results the replica to truncate its entire log to 0
> and hence initiates fetching of terabytes of data from the lead broker, which
> sometimes leads to hours of downtime. We observed the bad cases that the
> reset offset can propagate to recovery-point-offset-checkpoint file, making a
> lead broker to truncate the file. This seems to have the potential to lead to
> data loss if the truncation happens at both follower and leader brokers.
> This is the particular faulty scenario manifested in our tests:
> # The broker restarts and receive LeaderAndIsr from the controller
> # LeaderAndIsr message however does not contain all the partitions (probably
> because other brokers were churning at the same time)
> # becomeLeaderOrFollower calls getOrCreatePartition and updates the
> allPartitions with the partitions included in the LeaderAndIsr message {code}
> def getOrCreatePartition(topic: String, partitionId: Int): Partition = {
> var partition = allPartitions.get((topic, partitionId))
> if (partition == null) {
> allPartitions.putIfNotExists((topic, partitionId), new Partition(topic,
> partitionId, time, this))
> {code}
> # replication-offset-checkpoint jumps in taking a snapshot of (the partial)
> allReplicas' high watermark into replication-offset-checkpoint file {code}
> def checkpointHighWatermarks() {
> val replicas =
> allPartitions.values.map(_.getReplica(config.brokerId)).collect{case
> Some(replica) => replica}{code} hence rewriting the previous highwatermarks.
> # Later becomeLeaderOrFollower calls makeLeaders and makeFollowers which read
> the (now partial) file through Partition::getOrCreateReplica {code}
> val checkpoint =
> replicaManager.highWatermarkCheckpoints(log.dir.getParentFile.getAbsolutePath)
> val offsetMap = checkpoint.read
> if (!offsetMap.contains(TopicAndPartition(topic, partitionId)))
> info("No checkpointed highwatermark is found for partition
> [%s,%d]".format(topic, partitionId))
> {code}
> We are not entirely sure whether the initial LeaderAndIsr message including a
> subset of partitions is critical in making this race condition manifest or
> not. But it is an important detail since it clarifies that a solution based
> on not letting the highwatermark-checkpoint thread jumping in the middle of
> processing a LeaderAndIsr message would not suffice.
> The solution we are thinking of is to force initializing allPartitions by the
> partitions listed in the replication-offset-checkpoint (and perhaps
> recovery-point-offset-checkpoint file too) when a server starts.
> Thoughts?
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