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https://issues.apache.org/jira/browse/HDFS-3828?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13449340#comment-13449340
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Andy Isaacson commented on HDFS-3828:
-------------------------------------
bq. Per the findbugs warnning I'd pull your new check in scanBlockPoolSlice out
to a synchronized method (eg workRemainingInCurrentPeriod)
Done.
bq. DataBlockScanner#run should use SLEEP_PERIOD_MS
done.
bq. In getTotalScans rather than throw IOE if given a bpid w/o a scanner I
believe this should be an assert (we should always have a scanner for a block
pool if we've enbabled scanning, which we have if we're in DataBlockScanner)
There are at least 6 similar tests, and one of them is:
{code}
88 BlockPoolSliceScanner bpScanner = getNextBPScanner(currentBpId);
89 if (bpScanner == null) {
90 // Possible if thread is interrupted
{code}
so I'm inclined to keep it as is; making one of these tests into an assert
seems jarring to me.
> Block Scanner rescans blocks too frequently
> -------------------------------------------
>
> Key: HDFS-3828
> URL: https://issues.apache.org/jira/browse/HDFS-3828
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 0.23.0, 2.0.0-alpha
> Reporter: Andy Isaacson
> Assignee: Andy Isaacson
> Attachments: hdfs-3828-1.txt, hdfs-3828-2.txt, hdfs-3828-3.txt,
> hdfs3828.txt
>
>
> {{BlockPoolSliceScanner#scan}} calls cleanUp every time it's invoked from
> {{DataBlockScanner#run}} via {{scanBlockPoolSlice}}. But cleanUp
> unconditionally roll()s the verificationLogs, so after two iterations we have
> lost the first iteration of block verification times. As a result a cluster
> with just one block repeatedly rescans it every 10 seconds:
> {noformat}
> 2012-08-16 15:59:57,884 INFO datanode.BlockPoolSliceScanner
> (BlockPoolSliceScanner.java:verifyBlock(391)) - Verification succeeded for
> BP-2101131164-172.29.122.91-1337906886255:blk_7919273167187535506_4915
> 2012-08-16 16:00:07,904 INFO datanode.BlockPoolSliceScanner
> (BlockPoolSliceScanner.java:verifyBlock(391)) - Verification succeeded for
> BP-2101131164-172.29.122.91-1337906886255:blk_7919273167187535506_4915
> 2012-08-16 16:00:17,925 INFO datanode.BlockPoolSliceScanner
> (BlockPoolSliceScanner.java:verifyBlock(391)) - Verification succeeded for
> BP-2101131164-172.29.122.91-1337906886255:blk_7919273167187535506_4915
> {noformat}
> {quote}
> To fix this, we need to avoid roll()ing the logs multiple times per period.
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