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From Azuryy Yu <azury...@gmail.com>
Subject Re: Time until a datanode is marked as dead
Date Mon, 26 Jan 2015 09:46:29 GMT
Hi Frank,

can you file an issue to add this configuration to the hdfs-default.xml?

On Mon, Jan 26, 2015 at 5:39 PM, Frank Lanitz <frank.lanitz@sql-ag.de>
wrote:

> Hi,
>
> Am 23.01.2015 um 19:23 schrieb Chris Nauroth:
> > The time period for determining if a datanode is dead is calculated as a
> > function of a few different configuration properties.  The current
> > implementation in DatanodeManager.java does it like this:
> >
> >     final long heartbeatIntervalSeconds = conf.getLong(
> >         DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_KEY,
> >         DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_DEFAULT);
> >     final int heartbeatRecheckInterval = conf.getInt(
> >         DFSConfigKeys.DFS_NAMENODE_HEARTBEAT_RECHECK_INTERVAL_KEY,
> >         DFSConfigKeys.DFS_NAMENODE_HEARTBEAT_RECHECK_INTERVAL_DEFAULT);
> > // 5 minutes
> >     this.heartbeatExpireInterval = 2 * heartbeatRecheckInterval
> >         + 10 * 1000 * heartbeatIntervalSeconds;
>
>
> Good to know.
>
> > Under default configuration, dfs.namenode.heartbeat.recheck-interval is
> > 5 minutes and dfs.heartbeat.interval is 3 seconds.  If we plug those
> > values into the formula, we get 10.5 minutes, which agrees with your
> > observation.  If you change dfs.namenode.heartbeat.recheck-interval to
> > 2.5 minutes, then you'll achieve an effective timeout of 5.5 minutes
> > before a datanode is marked dead.
> >
> > dfs.namenode.heartbeat.recheck-interval is not documented in
> > hdfs-default.xml, though I don't recall if that's an intentional choice
> > or just an oversight.  The value of the property must be expressed in
> > milliseconds.
>
> This did the trick. Thank you very much. For testing porpuse I've set it
> to 10000 and after approx 45s the node was marked as dead.
>
> Any chance to get this into a documented preference so possible behavior
> changes with future releases can be spotted before staging area.
>
> cheers,
> Frank
>

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