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From "Liu Shaohui (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-11218) Data loss in HBase standalone mode
Date Wed, 21 May 2014 03:27:38 GMT
Liu Shaohui created HBASE-11218:

             Summary: Data loss in HBase standalone mode
                 Key: HBASE-11218
                 URL: https://issues.apache.org/jira/browse/HBASE-11218
             Project: HBase
          Issue Type: Bug
            Reporter: Liu Shaohui
             Fix For: 0.99.0

Data loss in HBase standalone mode.
*How to produce it*
# Start HBase standalone mode.
# Create a table using hbase shell.
# Scan '.META.' and you will find data in meta table
# Kill the HBase process with -9 option
# Start the HBase agaion
# Scan '.META.' and you will find nothing in meta table.

*There are three main reasons.*
# FSDataOutputStream.sync should call flush() if the underlying wrapped stream is not Syncable.
See HADOOP-8861
# writeChecksum is ture in  default LocalFileSystem and the ChecksumFSOutputSummer will buffer
the data, which make the waledits are not written to os's filesystem with sync method immediately,
and those edits will be lost in regionserver's failover.
#  The MiniZooKeeperCluster deletes the old zk data at startup which maye cause data loss
in meta table. The failover procedure is: split pre root regionserver's hlog -> assign
root -> split pre meta regionserver's hlog -> assign meta -> split all other regionservers'
hlogs -> assign other regions. If there is no data in zookeeper, we will get null for root
regionserver and then assign root table. Some data in root table maybe be lost for some root's
WalEdits have not been splited and replayed. So does the Meta table.

I finished the patch for 0.94 and am working on the patch for trunk. Suggestions are welcomed.

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