hadoop-hdfs-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Created: (HDFS-1104) Fsck triggers full GC on NameNode
Date Wed, 21 Apr 2010 22:12:54 GMT
Fsck triggers full GC on NameNode
---------------------------------

                 Key: HDFS-1104
                 URL: https://issues.apache.org/jira/browse/HDFS-1104
             Project: Hadoop HDFS
          Issue Type: Bug
            Reporter: Hairong Kuang
             Fix For: 0.20.3


A NameNode at one of our clusters fell into full GC while fsck was performed. Digging into
the problem shows that it is caused by how NameNode handles the access time of a file.

Fsck calls open on every file in the checked directory to get the file's block locations.
Each open changes the file's access time and then leads to writing a transaction entry to
the edit log. The current code optimizes open so that it returns without issuing synchronizing
the edit log to the disk. It happened that in our cluster no other jobs were running while
fsck was performed. No edit log sync was ever called. So all open transactions were kept in
memory. When the edit log buffer got full, it automatically doubled its space by allocating
a new buffer.  Full GC happened when no contiguous space were found when allocating a new
bigger buffer.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


Mime
View raw message