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https://issues.apache.org/jira/browse/KAFKA-3587?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15273457#comment-15273457
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Jun Rao commented on KAFKA-3587:
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[~alekar] and [~liquanpei], thanks for both your patches. Overall, I feel that
[~alekar]'s approach is better. It tries to fit as many segments as possible
when building the map at the expense of perhaps wasting the read of the last
segment. However, if the last segment does fit, it eliminates one round of
extra scanning of all cleaned log. So, it seems to pay off overall. A few
comments on the patch.
1. In LogCleaner.buildOffsetMap(), we should throw an exception if the first
segment can't fit into the map. The exception should include information on
what the user should do to fix the problem.
2. In LogCleaner.buildOffsetMap(), we should stop taking new segments as soon
as a segment's scratchMap can't be merged into the offsetMap.
3. We probably want to keep the OffsetMap interface since it can make unit test
easier.
> 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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