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https://issues.apache.org/jira/browse/HDFS-6452?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14010672#comment-14010672
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Gera Shegalov commented on HDFS-6452:
-------------------------------------
Lohit is correct, when we implement "readable standby" similar to what is
provided by some database systems, the fraction of failed requests even in
"normal case" will be well below 50%. Making randomization optional is a good
idea.
> ConfiguredFailoverProxyProvider should randomize currentProxyIndex on
> initialization
> ------------------------------------------------------------------------------------
>
> Key: HDFS-6452
> URL: https://issues.apache.org/jira/browse/HDFS-6452
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: ha, hdfs-client
> Affects Versions: 2.4.0
> Reporter: Gera Shegalov
> Assignee: Gera Shegalov
>
> We observe that the clients iterate proxies in the fixed order. Depending on
> the order of namenodes in dfs.ha.namenodes.<nameservice> (e.g. 'nn1,nn2') and
> the current standby (nn1), all the clients will hit nn1 first, and then
> failover to nn2. Chatting with [~lohit] we think we can simply select the
> initial value of {{currentProxyIndex}} randomly, and keep the logic of
> {{performFailover}} of iterating from left-to-right. This should halve the
> unnecessary load on standby NN.
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