[
https://issues.apache.org/jira/browse/KAFKA-3693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15316991#comment-15316991
]
Maysam Yabandeh edited comment on KAFKA-3693 at 6/10/16 3:57 AM:
-----------------------------------------------------------------
*update:* broker 16 started shutting down at 06:15:16,582. Refer to this
[comment|https://issues.apache.org/jira/browse/KAFKA-3693?focusedCommentId=15315055&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15315055]
for details.
My apology. That was a copy-paste error. Broker 16 started shutting down at
05:40:46,845
{code}
2016-05-10 05:40:46,845 INFO server.ReplicaFetcherThread:
[ReplicaFetcherThread-0-15], Shutting down
{code}
until it completely shutdown at 06:17:27,160
{code}
2016-05-10 06:17:27,160 INFO server.KafkaServer: [Kafka Server 16], shut down
completed
{code}
So it seems that the controller is sending the LeaderAndIsr request but the
message is not delivered since broker 16 is being shut down. Instead the
controller retries until the broker is fully restarted and then the message is
delivered.
Did this correction resolve the confusion?
was (Author: maysamyabandeh):
My apology. That was a copy-paste error. Broker 16 started shutting down at
05:40:46,845
{code}
2016-05-10 05:40:46,845 INFO server.ReplicaFetcherThread:
[ReplicaFetcherThread-0-15], Shutting down
{code}
until it completely shutdown at 06:17:27,160
{code}
2016-05-10 06:17:27,160 INFO server.KafkaServer: [Kafka Server 16], shut down
completed
{code}
So it seems that the controller is sending the LeaderAndIsr request but the
message is not delivered since broker 16 is being shut down. Instead the
controller retries until the broker is fully restarted and then the message is
delivered.
Did this correction resolve the confusion?
> 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?
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
