nkeywal created HBASE-6401:
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Summary: HBase may lose edits after a crash if used with HDFS
1.0.3 or older
Key: HBASE-6401
URL: https://issues.apache.org/jira/browse/HBASE-6401
Project: HBase
Issue Type: Bug
Components: regionserver
Affects Versions: 0.96.0
Environment: all
Reporter: nkeywal
Priority: Critical
This comes from a hdfs bug, fixed in some hdfs versions. I haven't found the
hdfs jira for this.
Context: HBase Write Ahead Log features. This is using hdfs append. If the node
crashes, the file that was written is read by other processes to replay the
action.
- So we have in hdfs one (dead) process writing with another process reading.
- But, despite the call to syncFs, we don't always see the data when we have a
dead node. It seems to be because the call in DFSClient#updateBlockInfo ignores
the ipc errors and set the length to 0.
- So we may miss all the writes to the last block if we try to connect to the
dead DN.
hdfs 1.0.3, branch-1 or branch-1-win: we have the issue
http://svn.apache.org/viewvc/hadoop/common/branches/branch-1/src/hdfs/org/apache/hadoop/hdfs/DFSClient.java?revision=1359853&view=markup
hdfs branch-2 or trunk: we should not have the issue (but not tested)
http://svn.apache.org/viewvc/hadoop/common/branches/branch-2/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSInputStream.java?view=markup
The attached test will fail ~50 of the time.
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