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Posted to common-dev@hadoop.apache.org by "Philip Zeyliger (Created) (JIRA)" <ji...@apache.org> on 2012/04/19 01:46:39 UTC

[jira] [Created] (HADOOP-8292) TableMapping does not refresh when topology is updated

TableMapping does not refresh when topology is updated
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                 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


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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