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https://issues.apache.org/jira/browse/KAFKA-3410?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15198342#comment-15198342
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James Cheng commented on KAFKA-3410:
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1. Hm, you're right, I did say that, didn't I? So what's the way to prevent
this?
"Don't format your hard drive without an active replica"?
Or maybe:
"Just because you set replication-factor=2, doesn't mean that it is actively
being replicated, you have to make sure that the ISR is good"?
2. Any thought on my question #2?
> 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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