[jira] [Issue Comment Edited] (CASSANDRA-2552) ReadResponseResolver Race

["Stu Hood (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-2552?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13025086#comment-13025086 ] 

Stu Hood edited comment on CASSANDRA-2552 at 4/26/11 6:19 AM:
--------------------------------------------------------------

Here is a cut down testcase that reproduces the race: it looks like two threads can race on step 2 such that neither accounts for the item added by the other, and both think the set of responses is too small.

I have a patch that makes append + size an atomic operation: I'll post it as soon as I clean it up a bit.

      was (Author: stuhood):
    Here is a cut down testcase that reproduces the race: it looks like two threads can race on step 2 such that they neither accounts for the item added by the other, and both think the set of responses is too small.

I have a patch that makes append + size an atomic operation: I'll post it as soon as I clean it up a bit.
  
> ReadResponseResolver Race
> -------------------------
>
>                 Key: CASSANDRA-2552
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2552
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Stu Hood
>            Assignee: Stu Hood
>             Fix For: 0.8.0
>
>         Attachments: ResolveRaceTest.java
>
>
> When receiving a response, ReadResponseResolver uses a 3 step process to decide whether to trigger the condition that enough responses have arrived:
> # Add new response
> # Check response set size
> # Check that data is present
> I think that these steps must have been reordered by the compiler in some cases, because I was able to reproduce a case for a QUORUM read where the condition is not properly triggered:
> {noformat}
> INFO [RequestResponseStage:15] 2011-04-25 00:26:53,514 ReadResponseResolver.java (line 87) post append for 1087367065: hasData=false in 2 messages
> INFO [RequestResponseStage:8] 2011-04-25 00:26:53,514 ReadResponseResolver.java (line 87) post append for 1087367065: hasData=true in 1 messages
> INFO [pool-1-thread-54] 2011-04-25 00:27:03,516 StorageProxy.java (line 623) Read timeout: java.util.concurrent.TimeoutException: ReadResponseResolver@1087367065(/10.34.131.109=false,/10.34.132.122=true,)
> {noformat}
> The last line shows that both results were present, and that one of them was holding data.

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