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https://issues.apache.org/jira/browse/HDFS-3153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13398025#comment-13398025
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Tsz Wo (Nicholas), SZE commented on HDFS-3153:
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Here is a proposal.
A volume name is first resolved with conf and then DNS. It could be resolved
into one or more hostnames. Multiple hostnames is used in HA setup.
Consider the URI hdfs://V/, where V is a volume name. If V is a volume name in
conf, resolve it with conf and then resolve it with DNS. Otherwise, resolve it
directly with DNS.
Consider the following conf setup:
{noformat}
dfs.namespace.volume.<v1>.hdfs = v1host:rpc_port
dfs.namespace.volume.<v1>.hftp = v1host:http_port
dfs.namespace.volume.<v1>.webhdfs = v1host:http_port
dfs.namespace.volume.<v2>.hdfs = v2host:rpc_port
dfs.namespace.volume.<v2>.hftp = v2host:http_port
dfs.namespace.volume.<v2>.webhdfs = v2host:http_port
{noformat}
Then, the logical namespaces are mapped to physical hosts during FileSystem
initialization as follows:
{noformat}
hdfs://v1/path => hdfs://v1host:v1rpc_port/path
hdfs://v1:port/path => hdfs://v1host:port/path
hftp://v1/path => hftp://v1host:v1http_port/path
webhdfs://v1/path => webhdfs://v1host:v1http_port/path
{noformat}
For HA, the configuration becomes:
{noformat}
dfs.namespace.volume.<v1>.hdfs = v1host1:rpc_port, v1host2:rpc_port
dfs.namespace.volume.<v1>.hftp = v1host1:http_port, v1host2:http_port
dfs.namespace.volume.<v1>.webhdfs = v1host1:http_port, v1host2:http_port
dfs.namespace.volume.<v2>.hdfs = v2host1:rpc_port, v2host2:rpc_port
dfs.namespace.volume.<v2>.hftp = v2host1:http_port, v2host2:http_port
dfs.namespace.volume.<v2>.webhdfs = v2host1:http_port, v2host2:http_port
{noformat}
> For HA, a logical name is visible in URIs - add an explicit logical name
> ------------------------------------------------------------------------
>
> Key: HDFS-3153
> URL: https://issues.apache.org/jira/browse/HDFS-3153
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 2.0.0-alpha
> Reporter: Sanjay Radia
> Assignee: Tsz Wo (Nicholas), SZE
> Priority: Critical
>
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