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Hadoop, mail # dev - Web UI for Active and Standby NN do not agree on safe mode setting


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Scott Forman 2013-05-10, 15:53
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Re: Web UI for Active and Standby NN do not agree on safe mode setting
Aaron T. Myers 2013-05-10, 18:35
Hi Scott,

This is actually working as intended. NN safemode is not a system-wide
state - it can be set independently on both the active and standby NNs.
DistributedFileSystem is indeed "doing the right thing" in that it will
return the safemode value of the active NN, but on the web UI each NN
should display its own safemode state, which might differ from the other's.
You might take a look at the discussion/patch in
https://issues.apache.org/jira/browse/HDFS-3507 for some more background
here.

Best,
Aaron
--
Aaron T. Myers
Software Engineer, Cloudera
On Fri, May 10, 2013 at 8:53 AM, Scott Forman <[EMAIL PROTECTED]>wrote:

> When safe mode is entered using the dfsadmin CLI command, only one of the
> Web UI's for the Namenodes in an HA environment seems to show that safe
> mode is on.  But retrieving the safe mode setting through the CLI (i.e.
> running "hdfs dfsadmin -safemode get") seems to display the correct setting
> when run from any node in the cluster.
>
> I noticed this problem when upgrading from a non-HA environment to an HA
> environment, and in this case, the NN in the pre-upgraded system always
> shows the correct setting, regardless if it is active or standby, while the
> newly added NN never displays that safe mode is on.
>
> The dfsadmin command uses DistributedFileSystem to get the setting, while
> the Web UI seems to use FSNamesystem.
>
> Is this a bug, or do both UI's need to be consulted to determine the safe
> mode setting?
>
> Thanks,
> Scott
>