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From "James Clampffer (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-11758) libhdfs++: Catch exceptions thrown by runtime hooks
Date Thu, 11 May 2017 18:03:04 GMT

     [ https://issues.apache.org/jira/browse/HDFS-11758?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

James Clampffer updated HDFS-11758:
-----------------------------------
    Attachment: HDFS-11758.HDFS-8707.001.patch

Minor change to last patch because there was a bug in the tests.  TestReadEvent and TestReadEventThrow
were supposed to do two hdfsPread calls on the same FileHandle to ensure throwing in the read
handler wouldn't effect future reads.  Instead it was making a new FileHandle for the second
read attempt.

> libhdfs++: Catch exceptions thrown by runtime hooks
> ---------------------------------------------------
>
>                 Key: HDFS-11758
>                 URL: https://issues.apache.org/jira/browse/HDFS-11758
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: hdfs-client
>            Reporter: James Clampffer
>            Assignee: James Clampffer
>         Attachments: HDFS-11758.HDFS-8707.000.patch, HDFS-11758.HDFS-8707.001.patch
>
>
> Right now there's nothing to stop a user supplied event callback from throwing and unwinding
the stack on the asio worker thread.  This can lead to async filesystem operations that never
complete because the stack was unwound before setting up the next async io call.
> Best practice is to be really careful about what is done inside event hooks and callbacks:
don't throw, sleep, or anything else that might block.  I've seen a few issues pop up because
a hook was made for monitoring purposes and later on stuff that was able to throw was added
without realizing where the exception may end up.



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