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From "Alejandro Abdelnur (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-8292) TableMapping does not refresh when topology is updated
Date Wed, 09 May 2012 00:53:49 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-8292?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Alejandro Abdelnur updated HADOOP-8292:
---------------------------------------

    Attachment: HADOOP-8292.patch

adding a lazy reload check on resolve(), the reload check will check the mapping file for
changes using a configurable minimum interval (default value set to 10 secs).
                
> TableMapping does not refresh when topology is updated
> ------------------------------------------------------
>
>                 Key: HADOOP-8292
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8292
>             Project: Hadoop Common
>          Issue Type: Bug
>    Affects Versions: 2.0.0
>            Reporter: Philip Zeyliger
>            Assignee: Alejandro Abdelnur
>         Attachments: HADOOP-8292.patch
>
>
> HADOOP-7030 introduced TableMapping, an implementation of DNSToSwitchMapping which uses
a file to map from IPs/hosts to their racks.  It's intended to replace ScriptBasedMapping
for cases where the latter was just a complicated way of looking up the rack in a file.
> Though there was discussion of it on the JIRA, the TableMapping implementation is not
'refreshable'.  i.e., if you want to add a host to your cluster, and that host wasn't in the
topology file to begin with, it will never be added.
> TableMapping should refresh, either based on a command that can be executed, or, perhaps,
if the file on disk changes.
> I'll also point out that TableMapping extends CachedDNSToSwitchMapping, but, since it
does no refreshing, I don't see what the caching gets you: I think the cache ends up being
a second copy of the underlying map, always.

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