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https://issues.apache.org/jira/browse/HDFS-2713?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13192032#comment-13192032
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Uma Maheswara Rao G commented on HDFS-2713:
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Lastly i forgot to mention other point.i.e, We cached the active connection in
client in our internal version. So, that in the same JVM, every new client need
not perform failover. First client will perform failover and others will use
the same proxy.
Do you think this will help us to solve below case in this HA proposal( atleast
per JVM level) ?
{quote}
>From HA doc section 8.3
o Failover
time
is
longer
since
clients
always
talks
to
the
first
NN
(who
may
be
dead)
before
looking
up
new
address
of
NN.
{quote}
If yes, i will file separate JIRA and start work on that (also this point
should not block initial release).
Am i missing something here?
> HA : An alternative approach to clients handling Namenode failover.
> --------------------------------------------------------------------
>
> Key: HDFS-2713
> URL: https://issues.apache.org/jira/browse/HDFS-2713
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ha, hdfs client
> Affects Versions: HA branch (HDFS-1623)
> Reporter: Uma Maheswara Rao G
> Assignee: Uma Maheswara Rao G
>
> This is the approach for client failover which we adopted when we developed
> HA for Hadoop. I would like to propose thia approach for others to review &
> include in the HA implementation, if found useful.
> This is similar to the ConfiguredProxyProvider in the sense that the it takes
> the address of both the Namenodes as the input. The major differences I can
> see from the current implementation are
> 1) During failover, user threads can be controlled very accurately about *the
> time they wait for active namenode* to be available, awaiting the retry.
> Beyond this, the threads will not be made to wait; DFS Client will throw an
> Exception indicating that the operation has failed.
> 2) Failover happens in a seperate thread, not in the client application
> threads. The thread will keep trying to find the Active Namenode until it
> succeeds.
> 3) This also means that irrespective of whether the operation's RetryAction
> is RETRY_FAILOVER or FAIL, the user thread can trigger the client's failover.
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