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https://issues.apache.org/jira/browse/KAFKA-3410?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15338801#comment-15338801
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Maysam Yabandeh commented on KAFKA-3410:
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Seems that KAFKA-3861 is a slightly modified reincarnation of this issue.
Retrying with delay would not address the specific example in KAFKA-3861 as
either the crashed broker is down and there is no leader for the partition, or
if it is back up but cannot make progress since it is the only member of ISR
which is lower than the set min-in-sync-replica of 2. Moreover the crashed
broker (which is the only member of ISR) has genuinely lost data and there
should be a way to make it a follower if we want to avoid data loss.
Any thoughts on the approach proposed in KAFKA-3861?
bq. having the controller make an exception for this case: if ISR size is less
than min-in-sync-replicas and the new leader would be -1, then the controller
does an RPC to all the replicas and inquire of the latest offset, and if all
the replicas responded then chose the one with the largest offset as the leader
as well as the new ISR.
> Unclean leader election and "Halting because log truncation is not allowed"
> ---------------------------------------------------------------------------
>
> Key: KAFKA-3410
> URL: https://issues.apache.org/jira/browse/KAFKA-3410
> Project: Kafka
> Issue Type: Bug
> Reporter: James Cheng
>
> I ran into a scenario where one of my brokers would continually shutdown,
> with the error message:
> [2016-02-25 00:29:39,236] FATAL [ReplicaFetcherThread-0-1], Halting because
> log truncation is not allowed for topic test, Current leader 1's latest
> offset 0 is less than replica 2's latest offset 151
> (kafka.server.ReplicaFetcherThread)
> I managed to reproduce it with the following scenario:
> 1. Start broker1, with unclean.leader.election.enable=false
> 2. Start broker2, with unclean.leader.election.enable=false
> 3. Create topic, single partition, with replication-factor 2.
> 4. Write data to the topic.
> 5. At this point, both brokers are in the ISR. Broker1 is the partition
> leader.
> 6. Ctrl-Z on broker2. (Simulates a GC pause or a slow network) Broker2 gets
> dropped out of ISR. Broker1 is still the leader. I can still write data to
> the partition.
> 7. Shutdown Broker1. Hard or controlled, doesn't matter.
> 8. rm -rf the log directory of broker1. (This simulates a disk replacement or
> full hardware replacement)
> 9. Resume broker2. It attempts to connect to broker1, but doesn't succeed
> because broker1 is down. At this point, the partition is offline. Can't write
> to it.
> 10. Resume broker1. Broker1 resumes leadership of the topic. Broker2 attempts
> to join ISR, and immediately halts with the error message:
> [2016-02-25 00:29:39,236] FATAL [ReplicaFetcherThread-0-1], Halting because
> log truncation is not allowed for topic test, Current leader 1's latest
> offset 0 is less than replica 2's latest offset 151
> (kafka.server.ReplicaFetcherThread)
> I am able to recover by setting unclean.leader.election.enable=true on my
> brokers.
> I'm trying to understand a couple things:
> * In step 10, why is broker1 allowed to resume leadership even though it has
> no data?
> * In step 10, why is it necessary to stop the entire broker due to one
> partition that is in this state? Wouldn't it be possible for the broker to
> continue to serve traffic for all the other topics, and just mark this one as
> unavailable?
> * Would it make sense to allow an operator to manually specify which broker
> they want to become the new master? This would give me more control over how
> much data loss I am willing to handle. In this case, I would want broker2 to
> become the new master. Or, is that possible and I just don't know how to do
> it?
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