Datanode corruption if machine dies while writing VERSION file
--------------------------------------------------------------
Key: HADOOP-2073
URL: https://issues.apache.org/jira/browse/HADOOP-2073
Project: Hadoop
Issue Type: Bug
Affects Versions: 0.14.0
Reporter: Michael Bieniosek
Yesterday, due to a bad mapreduce job, some of my machines went on OOM killing
sprees and killed a bunch of datanodes, among other processes. Since my
monitoring software kept trying to bring up the datanodes, only to have the
kernel kill them off again, each machine's datanode was probably killed many
times. A large percentage of these datanodes will not come up now, and write
this message to the logs:
2007-10-18 00:23:28,076 ERROR org.apache.hadoop.dfs.DataNode:
org.apache.hadoop.dfs.InconsistentFSStateException: Directory /hadoop/dfs/data
is in an inconsistent state: file VERSION is invalid.
When I check, /hadoop/dfs/data/current/VERSION is an empty file. Consequently,
I have to delete all the blocks on the datanode and start over. Since the OOM
killing sprees happened simultaneously on several datanodes in my DFS cluster,
this could have crippled my dfs cluster.
I checked the hadoop code, and in org.apache.hadoop.dfs.Storage, I see this:
{{{
/**
* Write version file.
*
* @throws IOException
*/
void write() throws IOException {
corruptPreUpgradeStorage(root);
write(getVersionFile());
}
void write(File to) throws IOException {
Properties props = new Properties();
setFields(props, this);
RandomAccessFile file = new RandomAccessFile(to, "rws");
FileOutputStream out = null;
try {
file.setLength(0);
file.seek(0);
out = new FileOutputStream(file.getFD());
props.store(out, null);
} finally {
if (out != null) {
out.close();
}
file.close();
}
}
}}}
So if the datanode dies after file.setLength(0), but before props.store(out,
null), the VERSION file will get trashed in the corrupted state I see. Maybe
it would be better if this method created a temporary file VERSION.tmp, and
then copied it to VERSION, then deleted VERSION.tmp? That way, if VERSION was
detected to be corrupt, the datanode could look at VERSION.tmp to recover the
data.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
