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From "Zhe Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6648) Order of namenodes in ConfiguredFailoverProxyProvider is undefined
Date Thu, 23 Mar 2017 21:25:41 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6648?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15939252#comment-15939252

Zhe Zhang commented on HDFS-6648:

[~chris.douglas] Looks like the release note needs to be updated? Thanks.

> Order of namenodes in ConfiguredFailoverProxyProvider is undefined
> ------------------------------------------------------------------
>                 Key: HDFS-6648
>                 URL: https://issues.apache.org/jira/browse/HDFS-6648
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: ha, hdfs-client
>    Affects Versions: 2.7.0
>            Reporter: Rafal Wojdyla
>            Assignee: Inigo Goiri
>             Fix For: 2.9.0
>         Attachments: HDFS-6648-000.patch, HDFS-6648-001.patch
> 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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