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https://issues.apache.org/jira/browse/HADOOP-1985?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12564745#action_12564745
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devaraj edited comment on HADOOP-1985 at 2/1/08 11:04 AM:
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I am thinking of returning an RPC error (like DNA_UNRESOLVED). That will ensure
that RPC handlers are not held up unnecessarily on the namenode while the
resolution is in progress (which depends on when the resolution thread gets a
chance to run).
was (Author: devaraj):
I am thinking of returning an RPC error (like DNA_TRYREGISTERAGAIN). That
will ensure that RPC handlers are not held up unnecessarily on the namenode
while the resolution is in progress (which depends on when the resolution
thread gets a chance to run).
> Abstract node to switch mapping into a topology service class used by
> namenode and jobtracker
> ---------------------------------------------------------------------------------------------
>
> Key: HADOOP-1985
> URL: https://issues.apache.org/jira/browse/HADOOP-1985
> Project: Hadoop Core
> Issue Type: New Feature
> Components: dfs, mapred
> Reporter: eric baldeschwieler
> Assignee: Devaraj Das
> Fix For: 0.17.0
>
> Attachments: 1985.new.patch, 1985.v1.patch, 1985.v10.patch,
> 1985.v11.patch, 1985.v2.patch, 1985.v3.patch, 1985.v4.patch, 1985.v5.patch,
> 1985.v6.patch, 1985.v9.patch, jobinprogress.patch
>
>
> In order to implement switch locality in MapReduce, we need to have switch
> location in both the namenode and job tracker. Currently the namenode asks
> the data nodes for this info and they run a local script to answer this
> question. In our environment and others that I know of there is no reason to
> push this to each node. It is easier to maintain a centralized script that
> maps node DNS names to switch strings.
> I propose that we build a new class that caches known DNS name to switch
> mappings and invokes a loadable class or a configurable system call to
> resolve unknown DNS to switch mappings. We can then add this to the namenode
> to support the current block to switch mapping needs and simplify the data
> nodes. We can also add this same callout to the job tracker and then
> implement rack locality logic there without needing to chane the filesystem
> API or the split planning API.
> Not only is this the least intrusive path to building racklocal MR I can ID,
> it is also future compatible to future infrastructures that may derive
> topology on the fly, etc, etc...
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