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https://issues.apache.org/jira/browse/HDFS-988?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12835403#action_12835403
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dhruba borthakur commented on HDFS-988:
---------------------------------------
My proposal is to make the enterSafeMode method wait for all pending
transactions to get flushed.
{code}
synchronized void FSNamesystem.enterSafeMode() throws IOException {
if (!isInSafeMode()) {
safeMode = new SafeModeInfo();
return;
}
safeMode.setManual();
getEditLog().logSyncAll(); <======= new code here
NameNode.stateChangeLog.info("STATE* Safe mode is ON. "
+ safeMode.getTurnOffTip());
}
synchronized void FSEditLog.logSyncAll() throws IOException {
TransactionId id = myTransactionId.get();
id.txid = txid;
logSync();
}
{code}
> saveNamespace can corrupt edits log
> -----------------------------------
>
> Key: HDFS-988
> URL: https://issues.apache.org/jira/browse/HDFS-988
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: name-node
> Reporter: dhruba borthakur
>
> The adminstrator puts the namenode is safemode and then issues the
> savenamespace command. This can corrupt the edits log. The problem is that
> when the NN enters safemode, there could still be pending logSycs occuring
> from other threads. Now, the saveNamespace command, when executed, would save
> a edits log with partial writes. I have seen this happen on 0.20.
> https://issues.apache.org/jira/browse/HDFS-909?focusedCommentId=12828853&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12828853
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