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From "Harsh J (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6648) Order of namenodes in ConfiguredFailoverProxyProvider is not defined by order in hdfs-site.xml
Date Sun, 17 Aug 2014 09:13:18 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6648?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14099918#comment-14099918
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Harsh J commented on HDFS-6648:
-------------------------------

I don't think it was the design goal to have them being connected to in any order of configuration;
just based off a list in the configuration.

Is this posing a Major problem for you though? The proxy is invoked only during init and trouble
within an instance, not at every request.

> Order of namenodes in ConfiguredFailoverProxyProvider is not defined by order in hdfs-site.xml
> ----------------------------------------------------------------------------------------------
>
>                 Key: HDFS-6648
>                 URL: https://issues.apache.org/jira/browse/HDFS-6648
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: ha, hdfs-client
>    Affects Versions: 2.2.0
>            Reporter: Rafal Wojdyla
>
> In org.apache.hadoop.hdfs.server.namenode.ha.ConfiguredFailoverProxyProvider, in the
constructor, there's a map <nameservice : < service-id : service-rpc-address > >
(DFSUtil.getHaNnRpcAddresses). It's a LinkedHashMap of HashMaps. The order is kept for _nameservices_.
Then to find active namenode, for nameservice, we get HashMap of <service-id : service-rpc-address
> for requested nameservice (taken from URI request), And for this HashMap we get values
- order of this collection is not strictly defined! In the code: 
> {code}
> Collection<InetSocketAddress> addressesOfNns = addressesInNN.values(); 
> {code}
> And then we put these values (in not defined order) into ArrayList of proxies, and then
in getProxy we start from first proxy in the list and failover to next if needed. 
> It would make sense for ConfiguredFailoverProxyProvider to keep order of proxies/namenodes
defined in hdfs-site.xml.



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