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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (CASSANDRA-6052) memory exhaustion
Date Wed, 18 Sep 2013 09:02:53 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-6052?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Sylvain Lebresne resolved CASSANDRA-6052.
-----------------------------------------

    Resolution: Duplicate

This is a duplicate of CASSANDRA-4415 in the sense that CASSANDRA-4415 is the only reasonable
solution to this known problem.

When a use submit a query with either no limit or a huge one, the server has no way to know
how big the result will be in practice. So the only way to not OOM/exhaust memory is for the
result to be paged to the client chunks by chunks if it's too big. And that what CASSANDRA-4415
added to cassandra 2.0.

Unfortunately, such change require some adaptation of the client (it should use the native
protocol v2) and not all clients, including cqlsh (but work is underway to fix that), have
been updated yet. In the meantime, if you use a client that does not use the native protocol
v2, then you must be careful to not submit queries that would yield huge result set (you need
to use a reasonable limit and page in your application if needs be).

                
> memory exhaustion
> -----------------
>
>                 Key: CASSANDRA-6052
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6052
>             Project: Cassandra
>          Issue Type: Bug
>         Environment: Debian, Cassandra 2.0
>            Reporter: arnaud-lb
>             Fix For: 2.0.1
>
>         Attachments: jconsole.png
>
>
> Issuing queries such as "select * from huge_table limit 1000000000" or "copy hugetable
to ..." reliably exhausts cassandra's heap space. (In cqlsh, at least.)
> The JVM then get stuck in a Full GC loop, GC fails to free anything, cassandra is unresponsive
and never recovers.

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