[jira] [Created] (KAFKA-3894) Log Cleaner thread crashes and never restarts

["Tim Carey-Smith (JIRA)" <ji...@apache.org>]

Tim Carey-Smith created KAFKA-3894:
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             Summary: Log Cleaner thread crashes and never restarts
                 Key: KAFKA-3894
                 URL: https://issues.apache.org/jira/browse/KAFKA-3894
             Project: Kafka
          Issue Type: Bug
          Components: core
    Affects Versions: 0.9.0.1, 0.8.2.2
         Environment: Oracle JDK 8
Ubuntu Precise
            Reporter: Tim Carey-Smith


The log-cleaner thread can crash if the number of keys in a topic grows to be too large to fit into the dedupe buffer. 

The result of this is a log line: 
{quote}
broker=0 pri=ERROR t=kafka-log-cleaner-thread-0 at=LogCleaner \[kafka-log-cleaner-thread-0\], Error due to  java.lang.IllegalArgumentException: requirement failed: 9750860 messages in segment MY_FAVORITE_TOPIC-2/00000000000047580165.log but offset map can fit only 5033164. You can increase log.cleaner.dedupe.buffer.size or decrease log.cleaner.threads
{quote}

As a result, the broker is left in a potentially dangerous situation where cleaning of compacted topics is not running. 

It is unclear if the broader strategy for the {{LogCleaner}} is the reason for this upper bound, or if this is a value which must be tuned for each specific use-case. 

Of more immediate concern is the fact that the thread crash is not visible via JMX or exposed as some form of service degradation. 

Some short-term remediations we have made are:
* increasing the size of the dedupe buffer
* monitoring the log-cleaner threads inside the JVM



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