[jira] [Created] (HDFS-7492) If multiple threads call FsVolumeList#checkDirs at the same time, we should only do checkDirs once and give the results to all waiting threads

Mon, 08 Dec 2014 14:18:14 -0800 

Colin Patrick McCabe created HDFS-7492:
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             Summary: If multiple threads call FsVolumeList#checkDirs at the 
same time, we should only do checkDirs once and give the results to all waiting 
threads
                 Key: HDFS-7492
                 URL: https://issues.apache.org/jira/browse/HDFS-7492
             Project: Hadoop HDFS
          Issue Type: Improvement
            Reporter: Colin Patrick McCabe


checkDirs is called when we encounter certain I/O errors.  It's rare to get 
just a single I/O error... normally you start getting many errors when a disk 
is going bad.  For this reason, we shouldn't start a new checkDirs scan for 
each error.  Instead, if multiple threads call FsVolumeList#checkDirs at around 
the same time, we should only do checkDirs once and give the results to all the 
waiting threads.



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