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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8446) Lost writes when using lightweight transactions
Date Tue, 09 Dec 2014 20:21:14 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8446?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14239994#comment-14239994
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Sylvain Lebresne commented on CASSANDRA-8446:
---------------------------------------------

I'm afraid nothing in this description indicates a bug. Ligthweight transactions can throw
write timeouts and they will under heavy contention. And a greater replica factor does make
it somewhat more likely. It's something to be aware of and that your application should defend
against by handling those timeouts (which is not really specific to lightweigth transactions).
This is why lightweigth transactions are not recommended if you have lots of contention: they
just don't perform very well in this case as of the current implementation.

> Lost writes when using lightweight transactions
> -----------------------------------------------
>
>                 Key: CASSANDRA-8446
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8446
>             Project: Cassandra
>          Issue Type: Bug
>          Components: API, Core
>         Environment: Cassandra 2.1.2 on Java(TM) SE Runtime Environment (build 1.7.0_65-b17)
>            Reporter: Jochen Zeischka
>             Fix For: 2.1.3
>
>
> There's a serious problem when using lightweight transactions. Whenever th cluster gets
any load, write timeout exceptions start to occur and the client has no way to know whether
the write actually succeeded or not.
> I a simple test (https://gist.github.com/anonymous/4c83f2962b57fce4c3df) this results
in large percentages of lost writes (0 - 50%, depending on the load).
> The problem was described in https://stackoverflow.com/questions/27313360/how-can-we-avoid-losing-writes-when-using-lightweight-transactions-cas-in-cass



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