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From "Guozhang Wang (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 17:39:12 GMT

    [ https://issues.apache.org/jira/browse/KAFKA-3587?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15274418#comment-15274418
] 

Guozhang Wang commented on KAFKA-3587:
--------------------------------------

We have multiple PRs for this JIRA now, and I suggest we'd better centralize the discussion
in this ticket. [~junrao][~alekar][~ecomar].

> 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: 0.9.0.1
>         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 0.9.0.1, (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 0.9.0.1
> - 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
key:
> 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 
--print-data-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
error.
> [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
log.cleaner.threads
>         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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