[jira] [Commented] (KAFKA-2235) LogCleaner offset map overflow

["Joel Koshy (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-2235?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14971728#comment-14971728 ] 

Joel Koshy commented on KAFKA-2235:
-----------------------------------

While I think the change is well-motivated I'm not sure this is the right fix for this issue as the check is too conservative. i.e., especially with highly compressible messages the message-count in the segment may be extremely high but the unique-key-count may be low.

> LogCleaner offset map overflow
> ------------------------------
>
>                 Key: KAFKA-2235
>                 URL: https://issues.apache.org/jira/browse/KAFKA-2235
>             Project: Kafka
>          Issue Type: Bug
>          Components: core, log
>    Affects Versions: 0.8.1, 0.8.2.0
>            Reporter: Ivan Simoneko
>            Assignee: Ivan Simoneko
>             Fix For: 0.9.0.0
>
>         Attachments: KAFKA-2235_v1.patch, KAFKA-2235_v2.patch
>
>
> We've seen log cleaning generating an error for a topic with lots of small messages. It seems that cleanup map overflow is possible if a log segment contains more unique keys than empty slots in offsetMap. Check for baseOffset and map utilization before processing segment seems to be not enough because it doesn't take into account segment size (number of unique messages in the segment).
> I suggest to estimate upper bound of keys in a segment as a number of messages in the segment and compare it with the number of available slots in the map (keeping in mind desired load factor). It should work in cases where an empty map is capable to hold all the keys for a single segment. If even a single segment no able to fit into an empty map cleanup process will still fail. Probably there should be a limit on the log segment entries count?
> Here is the stack trace for this error:
> 2015-05-19 16:52:48,758 ERROR [kafka-log-cleaner-thread-0] kafka.log.LogCleaner - [kafka-log-cleaner-thread-0], Error due to
> java.lang.IllegalArgumentException: requirement failed: Attempt to add a new entry to a full offset map.
>        at scala.Predef$.require(Predef.scala:233)
>        at kafka.log.SkimpyOffsetMap.put(OffsetMap.scala:79)
>        at kafka.log.Cleaner$$anonfun$kafka$log$Cleaner$$buildOffsetMapForSegment$1.apply(LogCleaner.scala:543)
>        at kafka.log.Cleaner$$anonfun$kafka$log$Cleaner$$buildOffsetMapForSegment$1.apply(LogCleaner.scala:538)
>        at scala.collection.Iterator$class.foreach(Iterator.scala:727)
>        at kafka.utils.IteratorTemplate.foreach(IteratorTemplate.scala:32)
>        at scala.collection.IterableLike$class.foreach(IterableLike.scala:72)
>        at kafka.message.MessageSet.foreach(MessageSet.scala:67)
>        at kafka.log.Cleaner.kafka$log$Cleaner$$buildOffsetMapForSegment(LogCleaner.scala:538)
>        at kafka.log.Cleaner$$anonfun$buildOffsetMap$3.apply(LogCleaner.scala:515)
>        at kafka.log.Cleaner$$anonfun$buildOffsetMap$3.apply(LogCleaner.scala:512)
>        at scala.collection.immutable.Stream.foreach(Stream.scala:547)
>        at kafka.log.Cleaner.buildOffsetMap(LogCleaner.scala:512)
>        at kafka.log.Cleaner.clean(LogCleaner.scala:307)
>        at kafka.log.LogCleaner$CleanerThread.cleanOrSleep(LogCleaner.scala:221)
>        at kafka.log.LogCleaner$CleanerThread.doWork(LogCleaner.scala:199)
>        at kafka.utils.ShutdownableThread.run(ShutdownableThread.scala:60)



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