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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (KAFKA-3587) LogCleaner fails due to incorrect offset map computation on a replica
Date Fri, 06 May 2016 08:08:12 GMT

    [ https://issues.apache.org/jira/browse/KAFKA-3587?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15273777#comment-15273777

ASF GitHub Bot commented on KAFKA-3587:

GitHub user alekar opened a pull request:


    KAFKA-3587 Improve logic to build offsetMap in log.Cleaner.


You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/alekar/kafka trunk

Alternatively you can review and apply these changes as the patch at:


To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #1329
commit 1ec4f93656d4a67f42e90e776833a798034ace15
Author: Manas Alekar <malekar@netflix.com>
Date:   2016-05-05T23:03:26Z

    KAFKA-3587 Improve logic to build offsetMap in Cleaner.


> LogCleaner fails due to incorrect offset map computation on a replica
> ---------------------------------------------------------------------
>                 Key: KAFKA-3587
>                 URL: https://issues.apache.org/jira/browse/KAFKA-3587
>             Project: Kafka
>          Issue Type: Bug
>    Affects Versions:
>         Environment: Linux
>            Reporter: Kiran Pillarisetty
>            Assignee: Edoardo Comar
>         Attachments: 0001-POC-improving-deduping-segments.patch
> Log Cleaner fails to compact a segment even when the number of messages in it is less
than the offset map.
> In version, (LogCleaner.scala -> buildOffsetMap()), LogCleaner computes segment
size by subtracting segment's base offset from the latest offset ("segmentSize = segment.nextOffset()
- segment.baseOffset").  This works fine until you create another replica. When you create
a replica, it's segment could contain data which is already compacted on other brokers. Depending
up on the type of data, offset difference could be too big, larger than the offset map (maxDesiredMapSize),
and that causes LogCleaner to fail on that segment.
> Scenario:
> - Kafka
> - Cluster has two brokers.
> - Server.properties:
> log.cleaner.enable=true
> log.cleaner.dedupe.buffer.size=10485760 #10MB
> log.roll.ms=300000
> delete.topic.enable=true
> log.cleanup.policy=compact
> Steps to reproduce:
> 1. Create a topic with replication-factor of 1.
> ./kafka-topics.sh --zookeeper=localhost:2181 --create --topic test.log.compact.1M --partitions
1 --replication-factor 1 --config cleanup.policy=compact --config segment.ms=300000
> 2. Use kafka-console-producer.sh to produce a single message with the following key:
> LC1,{"test": "xyz"}
> 3. Use  kafka-console-producer.sh to produce a large number of messages with the following
> LC2,{"test": "abc"}
> 4. Let log cleaner run. Make sure log is compacted.  Verify with:
>  ./kafka-run-class.sh kafka.tools.DumpLogSegments  --files 00000000000000000000.log 
> Dumping 00000000000000000000.log
> Starting offset: 0
> offset: 0 position: 0 isvalid: true payloadsize: 11 magic: 0 compresscodec: NoCompressionCodec
crc: 3067045277 keysize: 11 key: LC1 payload: {"test": "xyz"}
> offset: 7869818 position: 48 isvalid: true payloadsize: 11 magic: 0 compresscodec: NoCompressionCodec
crc: 2668089711 keysize: 11 key: LC2 payload: {"test": "abc"}
> 5.  Increase Replication Factor to 2.  Followed these steps: http://kafka.apache.org/documentation.html#basic_ops_increase_replication_factor
> 6. Notice that log cleaner fails to compact the newly created replica with the following
> [2016-04-18 14:49:45,599] ERROR [kafka-log-cleaner-thread-0], Error due to  (kafka.log.LogCleaner)
> java.lang.IllegalArgumentException: requirement failed: 7206179 messages in segment test.log.compact.1M-0/00000000000000000000.log
but offset map can fit only 393215. You can increase log.cleaner.dedupe.buffer.size or decrease
>         at scala.Predef$.require(Predef.scala:219)
>         at kafka.log.Cleaner$$anonfun$buildOffsetMap$4.apply(LogCleaner.scala:584)
>         at kafka.log.Cleaner$$anonfun$buildOffsetMap$4.apply(LogCleaner.scala:580)
>         at scala.collection.immutable.Stream$StreamWithFilter.foreach(Stream.scala:570)
>         at kafka.log.Cleaner.buildOffsetMap(LogCleaner.scala:580)
>         at kafka.log.Cleaner.clean(LogCleaner.scala:322)
>         at kafka.log.LogCleaner$CleanerThread.cleanOrSleep(LogCleaner.scala:230)
>         at kafka.log.LogCleaner$CleanerThread.doWork(LogCleaner.scala:208)
>         at kafka.utils.ShutdownableThread.run(ShutdownableThread.scala:63)
> [2016-04-18 14:49:45,601] INFO [kafka-log-cleaner-thread-0], Stopped  (kafka.log.LogCleaner)
> 7. Examine the entries in the replica segment:
> ./kafka-run-class.sh kafka.tools.DumpLogSegments --files 00000000000000000000.log  --print-data-log
> There are only 218418 messages in that segment.
> However, Log Cleaner seems to think that there are 7206179 messages in that segment (as
per the above error)
> Error stems from this line in LogCleaner.scala:
> """val segmentSize = segment.nextOffset() - segment.baseOffset"""
> In Replica's log segment file ( 00000000000000000000.log), ending offset is 7206178.
Beginning offset is 0.  That makes Log Cleaner think that there are 7206179 messages in that
segment although there are only 218418 messages in it.
> IMO,  to address this kind of scenario, LogCleaner.scala should check for the number
of messages in the segment, instead of subtracting beginning offset from the ending offset.

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