[
https://issues.apache.org/jira/browse/HADOOP-1470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12502388
]
Raghu Angadi commented on HADOOP-1470:
--------------------------------------
readBuffer.java is tested in my dev environment. Checksumming closest to User I
think can be solved independently. I agree that it is very important and will
be solved for HADOOP-1134.
Some more considerations for InputChecker design:
If purpose of this Jira is to provide a generic InputChecker, I wonder why 2
streams (where it imposes that every checksum block be of the same size, for
eg.) is very generic. Does it support different types of checksums (DFS already
uses two types)? Are we confident this serves future FS well? Or is it ok to
modify InputChecker (probably all the existing FS'es) then?
When InputChecker reads 4k (say by some equivalent of readFully()), should DFS
necessarily read 256 MB of block data in the case where bytesPerChecksum is
64K to solve that? Of course no. This is just one example of various things DFS
support for this InputChecker needs to handle.
I have probably thought more than I should about this :). Back to HADOOP-1134.
> Rework FSInputChecker and FSOutputSummer to support checksum code sharing
> between ChecksumFileSystem and block level crc dfs
> ----------------------------------------------------------------------------------------------------------------------------
>
> Key: HADOOP-1470
> URL: https://issues.apache.org/jira/browse/HADOOP-1470
> Project: Hadoop
> Issue Type: Improvement
> Components: fs
> Affects Versions: 0.12.3
> Reporter: Hairong Kuang
> Assignee: Hairong Kuang
> Fix For: 0.14.0
>
>
> Comment from Doug in HADOOP-1134:
> I'd prefer it if the CRC code could be shared with CheckSumFileSystem. In
> particular, it seems to me that FSInputChecker and FSOutputSummer could be
> extended to support pluggable sources and sinks for checksums, respectively,
> and DFSDataInputStream and DFSDataOutputStream could use these. Advantages of
> this are: (a) single implementation of checksum logic to debug and maintain;
> (b) keeps checksumming as close to possible to data generation and use. This
> patch computes checksums after data has been buffered, and validates them
> before it is buffered. We sometimes use large buffers and would like to guard
> against in-memory errors. The current checksum code catches a lot of such
> errors. So we should compute checksums after minimal buffering (just
> bytesPerChecksum, ideally) and validate them at the last possible moment
> (e.g., through the use of a small final buffer with a larger buffer behind
> it). I do not think this will significantly affect performance, and data
> integrity is a high priority.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
