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Date: Mon, 13 Jun 2011 15:47:52 +0000 (UTC)
From: "Mck SembWever (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
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Subject: [jira] [Commented] (CASSANDRA-2755) ColumnFamilyRecordWriter fails
 to throw a write exception encountered after the user begins to close the
 writer
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    [ https://issues.apache.org/jira/browse/CASSANDRA-2755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13048604#comment-13048604 ] 

Mck SembWever commented on CASSANDRA-2755:
------------------------------------------

The check for the exception also occurs in ColumnFamilyRecordWriter.write(buf, value) -> RangeClient.put(pair)
Isn't it possible the put(..) is being called while the RangeClient thread is inside close() ?
(isn't write(..) called more often than close() ?)

For this reason inside RangeClient.run() i assigned lastException before calling close()

> ColumnFamilyRecordWriter fails to throw a write exception encountered after the user begins to close the writer
> ---------------------------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-2755
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2755
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Hadoop
>    Affects Versions: 0.8.0
>            Reporter: Greg Katz
>            Assignee: Mck SembWever
>         Attachments: 2755-v2.txt, CASSANDRA-2755.patch
>
>
> There appears to be a race condition in {{ColumnFamilyRecordWriter}} that can result in the loss of an exception. Here is how it can happen (W stands for the {{RangeClient}}'s worker thread; U stands for the {{ColumnFamilyRecordWriter}} user's thread):
> # W: {{RangeClient}}'s {{run}} method catches an exception originating in the Thrift client/socket, but doesn't get a chance to set it on the {{lastException}} field before it the thread is preempted.
> # U: The user calls {{close}} which calls {{stopNicely}}. Because the {{lastException}} field is null, {{stopNicely}} does not throw anything. {{close}} then joins on the worker thread.
> # W: The {{RangeClient}}'s {{run}} method sets the {{lastException}} field and exits.
> # U: Although the thread in {{close}} is waiting for the worker thread to exit, it has already checked the {{lastException}} field so it doesn't detect the presence of the last exception. Instead, {{close}} returns without throwing anything.
> This race condition means that intermittently write failures will go undetected.

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