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https://issues.apache.org/jira/browse/HDFS-4015?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14936226#comment-14936226
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Mingliang Liu commented on HDFS-4015:
-------------------------------------
# This patch looks good overall to me. The first assumption you made, aka the
_Generation Stamp_ of those blocks reported by a rejoining DN will be less than
the current highest generation stamp that is known to NN, makes sense to me.
# I agree with [~arpitagarwal] that this tip may not show up until the the
thresholds are reached. As it surpasses its following threshold message, once
the administrator sees this warning he/she may think that it is the right time
to run {{forceExit}} even before block thresholds are reached. Or we may need
to combine this warning with threshold message.
{code:title=FSNamesystem.java}
+ if(blockManager.getBytesInFuture() > 0) {
+ String msg = "Name node detected blocks with generation stamps " ...
+ return msg;
+ }
+
{code}
# I suppose the {{reached}} be 0 when we enter safemode, which stands for
{{safe mode is on, and threshold is not reached yet}}.
{code:title=FSNamesystem.java}
+ @VisibleForTesting
+ synchronized void enableSafeModeForTesting(Configuration conf) {
+ SafeModeInfo newSafemode = new SafeModeInfo(conf);
+ newSafemode.reached = 1;
+ this.safeMode = newSafemode;
+ }
{code}
> Safemode should count and report orphaned blocks
> ------------------------------------------------
>
> Key: HDFS-4015
> URL: https://issues.apache.org/jira/browse/HDFS-4015
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Affects Versions: 3.0.0
> Reporter: Todd Lipcon
> Assignee: Anu Engineer
> Attachments: HDFS-4015.001.patch, dfsAdmin-report_with_forceExit.png,
> dfsHealth.html.message.png
>
>
> The safemode status currently reports the number of unique reported blocks
> compared to the total number of blocks referenced by the namespace. However,
> it does not report the inverse: blocks which are reported by datanodes but
> not referenced by the namespace.
> In the case that an admin accidentally starts up from an old image, this can
> be confusing: safemode and fsck will show "corrupt files", which are the
> files which actually have been deleted but got resurrected by restarting from
> the old image. This will convince them that they can safely force leave
> safemode and remove these files -- after all, they know that those files
> should really have been deleted. However, they're not aware that leaving
> safemode will also unrecoverably delete a bunch of other block files which
> have been orphaned due to the namespace rollback.
> I'd like to consider reporting something like: "900000 of expected 1000000
> blocks have been reported. Additionally, 10000 blocks have been reported
> which do not correspond to any file in the namespace. Forcing exit of
> safemode will unrecoverably remove those data blocks"
> Whether this statistic is also used for some kind of "inverse safe mode" is
> the logical next step, but just reporting it as a warning seems easy enough
> to accomplish and worth doing.
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