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From "Jim Witschey (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9194) Delete-only workloads crash Cassandra
Date Wed, 15 Apr 2015 21:38:59 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9194?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14497058#comment-14497058
] 

Jim Witschey commented on CASSANDRA-9194:
-----------------------------------------

Thanks for the test, [~rwille@fold3.com]. I've rewritten it [as a dtest|https://github.com/riptano/cassandra-dtest/pull/236]
and reproduced the error, though not to an OOM. It [fails|https://gist.github.com/mambocab/08577841f4f74a722910]
on all 2.0 and 2.1 releases.

[~rwille@fold3.com], any luck finding the patch you were using? Looks like it was never merged
into a released version.

> Delete-only workloads crash Cassandra
> -------------------------------------
>
>                 Key: CASSANDRA-9194
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9194
>             Project: Cassandra
>          Issue Type: Bug
>         Environment: 2.0.14
>            Reporter: Robert Wille
>            Assignee: Jim Witschey
>             Fix For: 2.0.15
>
>
> The size of a tombstone is not properly accounted for in the memtable. A memtable which
has only tombstones will never get flushed. It will grow until the JVM runs out of memory.
The following program easily demonstrates the problem.
> {code}
> 		Cluster.Builder builder = Cluster.builder();
> 		
> 		Cluster c = builder.addContactPoints("cas121.devf3.com").build();
> 		
> 		Session s = c.connect();
> 			
> 		s.execute("CREATE KEYSPACE IF NOT EXISTS test WITH replication = { 'class' : 'SimpleStrategy',
'replication_factor' : 1 }");
> 		s.execute("CREATE TABLE IF NOT EXISTS test.test(id INT PRIMARY KEY)");
> 		PreparedStatement stmt = s.prepare("DELETE FROM test.test WHERE id = :id");
> 		int id = 0;
> 		
> 		while (true)
> 		{
> 			s.execute(stmt.bind(id));
> 			
> 			id++;
> 		}{code}
> This program should run forever, but eventually Cassandra runs out of heap and craps
out. You needn't wait for Cassandra to crash. If you run "nodetool cfstats test.test" while
it is running, you'll see Memtable cell count grow, but Memtable data size will remain 0.
> This issue was fixed once before. I received a patch for version 2.0.5 (I believe), which
contained the fix, but the fix has apparently been lost, because it is clearly broken, and
I don't see the fix in the change logs.



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