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https://issues.apache.org/jira/browse/HBASE-20674?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16500757#comment-16500757
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stack commented on HBASE-20674:
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isLocalFS is name of method, not of a boolean.... Make it localFS.
bq. If it's a local FS then we will always disable write checksums and verify
checksums, currently.
Can't hbase do its checksums even if localfs?
bq. So we are still writing the checksums but never reading them?
That is correct. If we fail the checksum that hbase wrote, we fall back to
check the hdfs one.
bq. Further tidied up the logic in v2 and added additional comments inline.
You verify your changes do as advertised -- or just unit tests? You change code
around in HFileSystem.java. There is a this.fs and and an fs. W/ your
reordering, the this.fs could be different?
Otherwise, looks great. Nice improvement. Thanks.
> clean up short circuit read logic and docs
> ------------------------------------------
>
> Key: HBASE-20674
> URL: https://issues.apache.org/jira/browse/HBASE-20674
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Affects Versions: 2.0.0
> Reporter: Mike Drob
> Assignee: Mike Drob
> Priority: Major
> Attachments: HBASE-20674.patch, HBASE-20674.v2.patch
>
>
> Mailing list discussion at
> https://lists.apache.org/thread.html/f6f73df0ceae29f762f9b9088e3ffd0bf8f109d3dd692df100bf4fd6@%3Cdev.hbase.apache.org%3E
> There are several inconsistencies between how our docs claim we do things and
> how we actually do things.
> There are two docs sections that attempt to address how SCR should work.
> dfs.client.read.shortcircuit.skip.checksum is advised to set to true, but our
> code in separate places ignores it and then later sets it to true anyway.
> CommonFSUtils and FSUtils duplicate code related to SCR setup.
> There is a workaround in HFileSystem for a bug that's been fixed in all
> versions of hadoop that we support. (HADOOP-9307)
> We suggest setting dfs.client.read.shortcircuit.buffer.size to a value that
> is very close to what we'd set it to anyway, without clearly explaining why
> this is important.
> There are other properties that we claim are important, but we don't offer
> any suggestions or explanations.
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