[HDFS-3828] Block Scanner rescans blocks too frequently

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.23.0
• Fix Version/s: 2.5.0
• Target Version/s: 0.23.0
• Assignee: Andy Isaacson
• Reporter: Andy Isaacson
• Created: 21/Aug/12 20:09
• Updated: 15/Aug/14 05:41
• Resolved: 29/Apr/14 14:44

Description

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:

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

To fix this, we need to avoid roll()ing the logs multiple times per period.

Issue Links

• is related to: HDFS-3194 DataNode block scanner is running too frequently
• relates to: HDFS-3902 TestDatanodeBlockScanner#testBlockCorruptionPolicy is broken