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From "Travis Crawford (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-7359) Pluggable interface for cluster membership
Date Sat, 04 Jun 2011 17:25:47 GMT
Pluggable interface for cluster membership
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                 Key: HADOOP-7359
                 URL: https://issues.apache.org/jira/browse/HADOOP-7359
             Project: Hadoop Common
          Issue Type: Improvement
            Reporter: Travis Crawford


Currently Hadoop uses local files to determine cluster membership. With HDFS for example,
dfs.hosts and dfs.hosts.exclude are used.

To enable tighter integrations cluster membership should be an interface, with the current
file-based functionality provided as the default implementation. The common case would be
no functional change, however, sites could plug an alternative implementation in, such as
pulling the machine lists from a machine database.

DETAILS:

Two machine lists, includes and excludes, are used to define cluster membership and state.
HostsFileReader currently handles reading these lists from files, who's names are passed in
by FSNamesystem for HDFS and JobTracker for MR.

The proposed change is adding a HostsReader interface to common, and changing HostsFileReader
to an abstract class that functions the same as today.

Two new classes, DFSHostsFileReader and MRHostsFileReader, extend HostsFileReader and simply
pass the appropriate file names in. These new classes are needed because config key names
live outside common.

Two new conf keys, defaulting to the file-based readers, would be added to choose a different
hosts reader: dfs.namenode.hosts.reader.class mapreduce.jobtracker.hosts.reader.class

Comments/suggestions? I have most of this written already but would love some feedback on
the general idea before posting the diff.

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