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From "Sven Ludwig (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (KAFKA-3039) Temporary loss of leader resulted in log being completely truncated
Date Fri, 23 Jun 2017 18:08:00 GMT

    [ https://issues.apache.org/jira/browse/KAFKA-3039?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16061326#comment-16061326
] 

Sven Ludwig commented on KAFKA-3039:
------------------------------------

I just observed this on Confluent Platform 3.2.1 with Kafka 0.10.2.1

For 907 (including some offset topics) out of 1263 topics the broker logged on restart:

{{INFO Truncating log <topic-partition> to offset 0. (kafka.log.Log)}}

During the broker's downtime, In this particular case, it was only missing leader for exactly
one partition. For all other partitions, other nodes were the leader.

This gave me the chills and I immediately shutdown the broker again. Now there is no missing
leader. I do not know if data was lost.


> Temporary loss of leader resulted in log being completely truncated
> -------------------------------------------------------------------
>
>                 Key: KAFKA-3039
>                 URL: https://issues.apache.org/jira/browse/KAFKA-3039
>             Project: Kafka
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 0.9.0.0
>         Environment: Debian 3.2.54-2 x86_64 GNU/Linux
>            Reporter: Imran Patel
>            Priority: Critical
>              Labels: reliability
>
> We had an event recently where the temporarily loss of a leader for a partition (during
a manual restart), resulted in the leader coming back with no high watermark state and truncating
its log to zero. Logs (attached below) indicate that it did have the data but not the commit
state. How is this possible?
> Leader (broker 3)
> [2015-12-18 21:19:44,666] INFO Completed load of log messages-14 with log end offset
14175963374 (kafka.log.Log)
> [2015-12-18 21:19:45,170] INFO Partition [messages,14] on broker 3: No checkpointed highwatermark
is found for partition [messages,14] (kafka.cluster.Partition)
> [2015-12-18 21:19:45,238] INFO Truncating log messages-14 to offset 0. (kafka.log.Log)
> [2015-12-18 21:20:34,066] INFO Partition [messages,14] on broker 3: Expanding ISR for
partition [messages,14] from 3 to 3,10 (kafka.cluster.Partition)
> Replica (broker 10)
> [2015-12-18 21:19:19,525] INFO Partition [messages,14] on broker 10: Shrinking ISR for
partition [messages,14] from 3,10,4 to 10,4 (kafka.cluster.Partition)
> [2015-12-18 21:20:34,049] ERROR [ReplicaFetcherThread-0-3], Current offset 14175984203
for partition [messages,14] out of range; reset offset to 35977 (kafka.server.ReplicaFetcherThread)
> [2015-12-18 21:20:34,033] WARN [ReplicaFetcherThread-0-3], Replica 10 for partition [messages,14]
reset its fetch offset from 14175984203 to current leader 3's latest offset 35977 (kafka.server.ReplicaFetcherThread)
> Some relevant config parameters:
>         offsets.topic.replication.factor = 3
>         offsets.commit.required.acks = -1
>         replica.high.watermark.checkpoint.interval.ms = 5000
>         unclean.leader.election.enable = false



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