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https://issues.apache.org/jira/browse/HADOOP-1528?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12508622
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Jim Kellerman commented on HADOOP-1528:
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See Michael's and my comments on HADOOP-1531
Why not have one HConnection object for each HBase instance?
Since the HConnection object is managing region to server mappings I guess it
makes sense to cache all the server information in the connection object rather
than just the root/meta information as I suggested previously.
My original thinking was that since what you call HTable is associated with a
single table, that it made sense to cache the information for that table here
instead of in the connection object. This way, when you are done with that
table, it's cache will go away when the HTable object goes away.
If you maintain the region to server cache for all the open tables for an HBase
instance in the HConnection, then there should probably a close method on
HTable so it can tell the connection to drop the information for that table.
> HClient for multiple 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.
> or
> 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 table, 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 minimum 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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