[
https://issues.apache.org/jira/browse/HDFS-1057?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12871497#action_12871497
]
Hairong Kuang commented on HDFS-1057:
-------------------------------------
Sam, the replica length in my comment meant the visible length so no new length
field is needed. The read algorithm in trunk simplifies the read algorithm in
the design doc.
A block reader does read until its disk length >= the request # of bytes. To
solve the last chunk CRC problem, I am thinking to store last chunk's crc in
ReplicaBeingWritten after the chunk is received. A block reader returns visible
length of bytes and last chunk crc from memory. This should work because # of
requested bytes <= disk length <= visible length.
> Concurrent readers hit ChecksumExceptions if following a writer to very end
> of file
> -----------------------------------------------------------------------------------
>
> Key: HDFS-1057
> URL: https://issues.apache.org/jira/browse/HDFS-1057
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: data-node
> Affects Versions: 0.21.0, 0.22.0
> Reporter: Todd Lipcon
> Assignee: sam rash
> Priority: Blocker
> Attachments: conurrent-reader-patch-1.txt,
> conurrent-reader-patch-2.txt, conurrent-reader-patch-3.txt
>
>
> In BlockReceiver.receivePacket, it calls replicaInfo.setBytesOnDisk before
> calling flush(). Therefore, if there is a concurrent reader, it's possible to
> race here - the reader will see the new length while those bytes are still in
> the buffers of BlockReceiver. Thus the client will potentially see checksum
> errors or EOFs. Additionally, the last checksum chunk of the file is made
> accessible to readers even though it is not stable.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
