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https://issues.apache.org/jira/browse/HADOOP-1470?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Doug Cutting updated HADOOP-1470:
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Status: Open (was: Patch Available)
1. Can you please examine the FindBugs warnings?
2. RawLocalFileSystem#open() and #create() ignore the bufferSize parameter.
This means that local file access will end up using only a buffer of
bytesPerChecksum, which will hurt performance.
3. ChecksumFileSystem#readChunk() always seeks the sums stream, even when it's
already in the right spot. Should we rely on implementations to optimize this?
I've seen seek implementations which are expensive even when the file position
is unchanged. RawLocalFileSystem will end up using FileChannel's
implementation, for which we have no source, so we'd need to benchmark it to
make sure that this is optimized.
> 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
>
> Attachments: GenericChecksum.patch, genericChecksum.patch,
> GenericChecksum1.patch, GenericChecksum2.patch, InputChecker-01.java
>
>
> 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.
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