[
https://issues.apache.org/jira/browse/HADOOP-3914?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Hairong Kuang updated HADOOP-3914:
----------------------------------
Attachment: checksumOk1.patch
Thanks Raghu for the comment. This patch adds "for the debugging purpose" in
the logging comment.
Christian, you are welcome! We want your patch to be committed so you have less
pain running HADOOP!
> checksumOk implementation in DFSClient can break applications
> -------------------------------------------------------------
>
> Key: HADOOP-3914
> URL: https://issues.apache.org/jira/browse/HADOOP-3914
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.17.1
> Reporter: Christian Kunz
> Assignee: Christian Kunz
> Priority: Blocker
> Fix For: 0.19.0
>
> Attachments: checksumOk.patch, checksumOk1.patch, patch.HADOOP-3914
>
>
> One of our non-map-reduce applications (written in C and using libhdfs to
> access dfs) stopped working after switch from 0.16 to 0.17.
> The problem was finally traced down to failures in checksumOk.
> I would assume, the purpose of checksumOk is for a DfsClient to indicate to a
> sending Datanode that the checksum of the received block is okay. This must
> be useful in the replication pipeline.
> How checksumOk is implemented is that any IOException is caught and ignored,
> probably because it is not essential for the client that the message is
> successful.
> But it proved fatal for our application because this application links in a
> 3rd-party library which seems to catch socket exceptions before libhdfs.
> Why was there an Exception? In our case the application reads a file into the
> local buffer of the DFSInputStream large enough to hold all data, the
> application reads to the end and the checksumOK is sent successfully at that
> time. But then the application does some other stuff and comes back to
> re-read the file (still open). It is then when it calls checksumOk again and
> crashes.
> It can easily be avoided by adding a Boolean making sure that checksumOk is
> called exactly once when EOS is encountered. Redundant calls to checksumOk do
> not seem to make sense anyhow.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
