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https://issues.apache.org/jira/browse/HBASE-3820?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13025044#comment-13025044
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Jieshan Bean commented on HBASE-3820:
-------------------------------------
Thanks stack.
I'm just taking some test to verify my modification. And after that, I will
commit the patch immediately.
> Splitlog() executed while the namenode was in safemode may cause data-loss
> --------------------------------------------------------------------------
>
> Key: HBASE-3820
> URL: https://issues.apache.org/jira/browse/HBASE-3820
> Project: HBase
> Issue Type: Bug
> Components: master
> Affects Versions: 0.90.2
> Reporter: Jieshan Bean
>
> I found this problem while the namenode went into safemode due to some
> unclear reasons.
> There's one patch about this problem:
> try {
> HLogSplitter splitter = HLogSplitter.createLogSplitter(
> conf, rootdir, logDir, oldLogDir, this.fs);
> try {
> splitter.splitLog();
> } catch (OrphanHLogAfterSplitException e) {
> LOG.warn("Retrying splitting because of:", e);
> // An HLogSplitter instance can only be used once. Get new instance.
> splitter = HLogSplitter.createLogSplitter(conf, rootdir, logDir,
> oldLogDir, this.fs);
> splitter.splitLog();
> }
> splitTime = splitter.getTime();
> splitLogSize = splitter.getSize();
> } catch (IOException e) {
> checkFileSystem();
> LOG.error("Failed splitting " + logDir.toString(), e);
> master.abort("Shutting down HBase cluster: Failed splitting hlog
> files...", e);
> } finally {
> this.splitLogLock.unlock();
> }
> And it was really give some useful help to some extent, while the namenode
> process exited or been killed, but not considered the Namenode safemode
> exception.
> I think the root reason is the method of checkFileSystem().
> It gives out an method to check whether the HDFS works normally(Read and
> write could be success), and that maybe the original propose of this method.
> This's how this method implements:
> DistributedFileSystem dfs = (DistributedFileSystem) fs;
> try {
> if (dfs.exists(new Path("/"))) {
> return;
> }
> } catch (IOException e) {
> exception = RemoteExceptionHandler.checkIOException(e);
> }
>
> I have check the hdfs code, and learned that while the namenode was in
> safemode ,the dfs.exists(new Path("/")) returned true. Because the file
> system could provide read-only service. So this method just checks the dfs
> whether could be read. I think it's not reasonable.
>
>
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