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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