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https://issues.apache.org/jira/browse/HADOOP-7030?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13235486#comment-13235486
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Steve Loughran commented on HADOOP-7030:
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Tom, could you have the class extend the cached mapping, the way the scripted
one does?
This would mean that
# the code to manage hash tables are in there
# on .23+ it will automatically pick up any extra features put into the base
class I added. E.g permitting providing info to callers about whether the
config is multi-switch, allowing callers to get/dump the topology map for
diagnostics, etc -yet the same code will work for both branches, and be a
better starting point for adding refresh operations.
# those bits of the code that check for the mapping being a cached mapping
won't wrap the mapping in another cache, so making it easier to do updates &C.
As you note, that bit of {{RackResolver}} should be fixed at some point -but
subclassing the cached mapper would do this automatically.
> new topology mapping implementations
> ------------------------------------
>
> Key: HADOOP-7030
> URL: https://issues.apache.org/jira/browse/HADOOP-7030
> Project: Hadoop Common
> Issue Type: New Feature
> Affects Versions: 0.20.1, 0.20.2, 0.21.0
> Reporter: Patrick Angeles
> Assignee: Tom White
> Attachments: HADOOP-7030-2.patch, HADOOP-7030.patch,
> HADOOP-7030.patch, topology.patch
>
>
> The default ScriptBasedMapping implementation of DNSToSwitchMapping for
> determining cluster topology has some drawbacks. Principally, it forks to an
> OS-specific script.
> This issue proposes two new Java implementations of DNSToSwitchMapping.
> TableMapping reads a two column text file that maps an IP or hostname to a
> rack ID. Ip4RangeMapping reads a three column text file where each line
> represents a start and end IP range plus a rack ID.
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