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https://issues.apache.org/jira/browse/HADOOP-1568?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12511242
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Doug Cutting commented on HADOOP-1568:
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> It will kill performance to require the copy planner to do a http head for
> each file
It should be significantly faster than the actual copy, no? The copy will need
to stat each file at open, which is the same number of namenode requests. So,
yes, it might significantly affect copy performance, but it shouldn't dominate.
Isn't that acceptable for a compatibility tool? Again, if we want to provide
optimal performance, then we'll need to expose more of the internals (like
block locations) and then the tool will be more fragile. If that's required,
then perhaps we should instead consider making the HDFS client and servers all
support multiple protocol versions.
> NameNode Schema for HttpFileSystem
> ----------------------------------
>
> Key: HADOOP-1568
> URL: https://issues.apache.org/jira/browse/HADOOP-1568
> Project: Hadoop
> Issue Type: New Feature
> Components: fs
> Reporter: Chris Douglas
> Assignee: Chris Douglas
>
> This issue will track the design and implementation of (the first pass of) a
> servlet on the namenode for querying its filesystem via HTTP. The proposed
> syntax for queries and responses is as follows.
> *Query*
> {noformat}GET http://<nn>:<port>/ls.jsp[<?option>[&option]*]
> HTTP/1.1{noformat}
> Where _option_ may be any of the following query parameters:
> _path_ : String (default: '/')
> _recursive_ : boolean (default: false)
> _filter_ : String (default: none)
> *Response*
> The response will be returned as an XML document in the following format:
> {noformat}
> <listing path="..." recursive="(yes|no)" filter="..."
> time="yyyy-MM-dd hh:mm:ss UTC" version="...">
> <directory path="..."/>
> <file path="..." modified="yyyy-MM-dd hh:mm:ss" blocksize="..."
> replication="..." size="..."
> dnurl="http://dn:port/streamFile?..."/>
> </listing>
> {noformat}
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