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https://issues.apache.org/jira/browse/HDFS-3828?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13449418#comment-13449418
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Eli Collins commented on HDFS-3828:
-----------------------------------
+1 latest patch is good to go. test failure is unrelated.
bq. so I'm inclined to keep it as is; making one of these tests into an assert
seems jarring to me.
assertions aren't jarring if you expect the assertion to hold. Do you agree
that the invariant (that we should never get a scanner for a block pool with no
scanner) should hold? If yes please file a follow on jira to address this case
and the other uses (where the invariant might hold as well). If not, then note
that printBlockReport and getNextBPScanner do *not* check for null so they will
NPE and we should fix them. Also, looks like the test checks the return value
to see if the scanners are initialized yet. Either way we can handle it in a
separate jira.
Also per my previous comment please file the jira for the proposed refactoring.
> 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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