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https://issues.apache.org/jira/browse/HADOOP-6078?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12721776#action_12721776
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Steve Loughran commented on HADOOP-6078:
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* You could do much of this just by taking down the specific nodes and bringing
them up again.
* Hot reconfig is tricky, for as todd points out, some values are cached
everywhere.
* Yet I'd like my TTs to be able to rebind to a JT that has just been brought
up on a different address.
At the very least, all the loops where workers spin waiting for their masters
should reread their configuration values every iteration. That way anything
that has subclassed Configuration to give live data could provide updated
locations
FWIW, although I've subclassed JobConf for my configuration, I stopped trying
to do live updates, as the objects end up being serialized and reread. I think
it would be really hard to do live reconfiguration with the current design.
Node restart is cleaner.
> Ability to re-configure hadoop daemons online
> ---------------------------------------------
>
> Key: HADOOP-6078
> URL: https://issues.apache.org/jira/browse/HADOOP-6078
> Project: Hadoop Core
> Issue Type: New Feature
> Components: mapred
> Reporter: Amar Kamat
>
> Example :
> Like we have _bin hadoop mradmin -refreshNodes_ we should also have _bin
> hadoop mradmin -reconfigure_ which re-configures mr while the cluster is
> online. Few parameters like job-expiry-interval etc can be changed in this
> way without having to restart the whole cluster.
> Master, once reconfigured, can ask the slaves to reconfigure (reload its
> config) from a well defined location on hdfs or via heartbeat.
> We can have some whitelisted configs that have _reloadable_ property.
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