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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (CASSANDRA-9194) Delete-only workloads crash Cassandra
Date Fri, 01 May 2015 10:36:06 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-9194?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Benedict resolved CASSANDRA-9194.
---------------------------------
    Resolution: Fixed

[~mambocab]: I've committed to trunk. Those metrics are indeed correct, I was just waiting
for an opinion on how to account for live data size in 2.1 (which is not a matter of correctness,
so is only slightly related to this bug but should be dealt with at the same time). I opted
to treat it as 8 bytes in 2.1, for the record.

> 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: Benedict
>             Fix For: 2.0.x
>
>         Attachments: 9194.2.txt, 9194.txt
>
>
> 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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