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https://issues.apache.org/jira/browse/HDFS-14118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16744572#comment-16744572
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Fengnan Li commented on HDFS-14118:
-----------------------------------
[~elgoiri] When I tried to write tests some new thoughts came to me: this
change doesn't bring too much benefits for the normal HA setup since for every
call from a client, there is a 50% chance it will go to the standby namenode
first, and these traffic are totally waste of time and network resource. This
is the downside of using DNS on an active-standby setup. (since standby is
normal here)
However, if we limit the scope to just routers, it makes more sense since
routers are all active-active, and none of the traffic is wasted. A client will
have a low chance of hitting standby router. (since standby is abnormal here)
Please suggest and thanks very much.
> Use DNS to resolve Namenodes and Routers
> ----------------------------------------
>
> Key: HDFS-14118
> URL: https://issues.apache.org/jira/browse/HDFS-14118
> Project: Hadoop HDFS
> Issue Type: New Feature
> Reporter: Fengnan Li
> Assignee: Fengnan Li
> Priority: Major
> Attachments: HDFS-14118.patch
>
>
> Clients will need to know about routers to talk to the HDFS cluster
> (obviously), and having routers updating (adding/removing) will have to make
> every client change, which is a painful process.
> DNS can be used here to resolve the single domain name clients knows to a
> list of routers in the current config. However, DNS won't be able to consider
> only resolving to the working router based on certain health thresholds.
> There are some ways about how this can be solved. One way is to have a
> separate script to regularly check the status of the router and update the
> DNS records if a router fails the health thresholds. In this way, security
> might be carefully considered for this way. Another way is to have the client
> do the normal connecting/failover after they get the list of routers, which
> requires the change of current failover proxy provider.
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