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From "James Kennedy (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-1528) HClient for multple-tables
Date Mon, 25 Jun 2007 21:27:25 GMT
HClient for multple-tables

                 Key: HADOOP-1528
                 URL: https://issues.apache.org/jira/browse/HADOOP-1528
             Project: Hadoop
          Issue Type: Task
          Components: contrib/hbase
    Affects Versions: 0.14.0
            Reporter: James Kennedy

I have an app that needs to access multiple HBase tables concurrently.  The current HClient
can only have one table open at a time even though it caches region servers of multiple tables
as they are looked up.

This means that my application layer must open multiple HClients, one per table, perhaps caching
those HClients in a pool to reuse them (and their cached table data) as appropriate.


Shall I write an HClient patch that makes the HClient  multi-table thread-safe?

Jim's suggestion is to implement an HClient singleton (call it HClientManager?) that does
the actual caching/resync of root/meta regions.  Individual HClients will still be one talbe,
one update row at a time but will rely on the singleton for the cached table info.  We want
HClients to be created and disposed as fast as possible with a minium of meta lookups.

Jim, what about non-root/meta regions, shouldn't they be cached and refreshed via the singleton
also?  It may still be possible that a region split/resync will occur during on HClient session
so does the HClientManager need to be able to notify the corresponding HClients in that event?

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