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https://issues.apache.org/jira/browse/CASSANDRA-13785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16139706#comment-16139706
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Romain Hardouin commented on CASSANDRA-13785:
---------------------------------------------

{code}
private static final int MAX_NUM_ENTRIES = Integer.MAX_VALUE / 40;
{code}

[~jay.zhuang] How did you find {{40}}? Maybe it's wise to name this number with 
a constant?

> Compaction fails for SSTables with large number of keys
> -------------------------------------------------------
>
>                 Key: CASSANDRA-13785
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13785
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Compaction
>            Reporter: Jay Zhuang
>            Assignee: Jay Zhuang
>
> Every a few minutes there're "LEAK DTECTED" messages in the log:
> {noformat}
> ERROR [Reference-Reaper:1] 2017-08-18 17:18:40,357 Ref.java:223 - LEAK 
> DETECTED: a reference 
> (org.apache.cassandra.utils.concurrent.Ref$State@3ed22d7) to class 
> org.apache.cassandra.utils.concurrent.WrappedSharedCloseable$Tidy@1022568824:[Memory@[0..159b6ba4),
>  Memory@[0..d8123468)] was not released before the reference was garbage 
> collected
> ERROR [Reference-Reaper:1] 2017-08-18 17:20:49,693 Ref.java:223 - LEAK 
> DETECTED: a reference 
> (org.apache.cassandra.utils.concurrent.Ref$State@6470405b) to class 
> org.apache.cassandra.utils.concurrent.WrappedSharedCloseable$Tidy@97898152:[Memory@[0..159b6ba4),
>  Memory@[0..d8123468)] was not released before the reference was garbage 
> collected
> ERROR [Reference-Reaper:1] 2017-08-18 17:22:38,519 Ref.java:223 - LEAK 
> DETECTED: a reference 
> (org.apache.cassandra.utils.concurrent.Ref$State@6fc4af5f) to class 
> org.apache.cassandra.utils.concurrent.WrappedSharedCloseable$Tidy@1247404854:[Memory@[0..159b6ba4),
>  Memory@[0..d8123468)] was not released before the reference was garbage 
> collected
> {noformat}
> Debugged the issue and found it's triggered by failed compactions, if the 
> compacted SSTable has more than 51m {{Integer.MAX_VALUE / 40}}) keys, it will 
> fail to create the IndexSummary: 
> [IndexSummary:84|https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/io/sstable/IndexSummary.java#L84].
> Cassandra compaction tried to compact every a few minutes and keeps failing.
> The root cause is while [creating 
> SafeMemoryWriter|https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/io/sstable/IndexSummaryBuilder.java#L112]
>  with {{> Integer.MAX_VALUE}} space, it returns the tailing 
> {{Integer.MAX_VALUE}} space 
> [SafeMemoryWriter.java:83|https://github.com/apache/cassandra/blob/6a1b1f26b7174e8c9bf86a96514ab626ce2a4117/src/java/org/apache/cassandra/io/util/SafeMemoryWriter.java#L83],
>  which makes the first 
> [entries.length()|https://github.com/apache/cassandra/blob/6a1b1f26b7174e8c9bf86a96514ab626ce2a4117/src/java/org/apache/cassandra/io/sstable/IndexSummaryBuilder.java#L173]
>  not 0. So the assert fails here: 
> [IndexSummary:84|https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/io/sstable/IndexSummary.java#L84]



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