[jira] [Created] (HDFS-6648) Order of namenodes in ConfiguredFailoverProxyProvider is not defined by order in hdfs-site.xml

["Rafal Wojdyla (JIRA)" <ji...@apache.org>]

Rafal Wojdyla created HDFS-6648:
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             Summary: 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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