[jira] Updated: (CASSANDRA-220) TCP writes get stuck

["Michael Greene (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-220?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Michael Greene updated CASSANDRA-220:
-------------------------------------

    Component/s: Core

> TCP writes get stuck
> --------------------
>
>                 Key: CASSANDRA-220
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-220
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Jun Rao
>            Assignee: Jun Rao
>             Fix For: 0.4
>
>         Attachments: 220-2.patch, 220-3.patch, 220-4.patch, 220-5.patch, issue220.patchv1
>
>
> In our test cluster, I observed that on some nodes, TCP writes get accumulated in TcpConnection.pendingWrites. However, the selector never gets a ready to write event. As a result, all writes get stuck. This is because write(message) and doPendingWrites() are not fully synchronized.  This following situation can happen:
> 1. write(message) adds stuff to pendingWrites.
> 2. a ready to write event happens; in doPendingWrites() buffered requests are written to socket
> 3. another write request happens, in write(message), the test for pendingWrites.isEmpty() is false
> 4. doPendingWrites() finishes writing all buffered request to socket
> 5. in write(message), the new request is added to pendingWrites
> Now, ready to write events will never happen again and all write requests get stuck in pendingWrites.

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