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https://issues.apache.org/jira/browse/HDFS-3886?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13451385#comment-13451385
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Harsh J commented on HDFS-3886:
-------------------------------
Yeah, sorry if my 'Shutdown requests' in title was too ambiguous. I am mostly
talking of the NN shutdown itself. I'd thought the simple init.d framework
itself had a kill -9'er (like a supervisor would) but I was wrong.
bq. This would indeed make an RPC to the NN to enter safemode, perform a save
namespace, and then shut itself down.
So this is currently a simple:
{code}
sudo -u hdfs hdfs dfsadmin -safemode enter
sudo -u hdfs hdfs dfsadmin -saveNamespace
{code}
However, my only caveat with this is that client logs for clients still active,
will start showing SafeModeExceptions rather than Connection Refused/etc.. Is
that fine to have, when doing a clean-stop? Would it be better if we shut off
the client RPC and then issued a namespace save?
I've also not thought of this in HA terms yet.
> Shutdown requests can possibly check for checkpoint issues (corrupted edits)
> and save a good namespace copy before closing down?
> --------------------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-3886
> URL: https://issues.apache.org/jira/browse/HDFS-3886
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: name-node
> Affects Versions: 2.0.0-alpha
> Reporter: Harsh J
> Priority: Minor
>
> HDFS-3878 sorta gives me this idea. Aside of having a method to download it
> to a different location, we can also lock up the namesystem (or deactivate
> the client rpc server) and save the namesystem before we complete up the
> shutdown.
> The init.d/shutdown scripts would have to work with this somehow though, to
> not kill -9 it when in-process. Also, the new image may be stored in a
> shutdown.chkpt directory, to not interfere in the regular dirs, but still
> allow easier recovery.
> Obviously this will still not work if all directories are broken. So maybe we
> could have some configs to tackle that as well?
> I haven't thought this through, so let me know what part is wrong to do :)
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