HBASE-11518 doc update for how to create non-shared HConnection (Qiang Tian)
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@ -44,24 +44,18 @@ import org.apache.hadoop.hbase.security.User;
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* connection.close();
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* }
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* }</pre>
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* <p>The following logic and API will be removed in the future:
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* <p>This class has a static Map of {@link HConnection} instances keyed by
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* {@link Configuration}; all invocations of {@link #getConnection(Configuration)}
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* that pass the same {@link Configuration} instance will be returned the same
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* {@link HConnection} instance (Adding properties to a Configuration
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* instance does not change its object identity; for more on how this is done see
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* {@link HConnectionKey}). Sharing {@link HConnection}
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* instances is usually what you want; all clients of the {@link HConnection}
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* instances share the HConnections' cache of Region locations rather than each
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* having to discover for itself the location of meta, etc. It makes
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* sense for the likes of the pool of HTables class {@link HTablePool}, for
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* instance (If concerned that a single {@link HConnection} is insufficient
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* for sharing amongst clients in say an heavily-multithreaded environment,
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* in practise its not proven to be an issue. Besides, {@link HConnection} is
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* implemented atop Hadoop RPC and as of this writing, Hadoop RPC does a
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* connection per cluster-member, exclusively).
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*
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* <p>But sharing connections makes clean up of {@link HConnection} instances a little awkward.
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* {@link HConnectionKey}; A {@link HConnectionKey} is identified by a set of
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* {@link Configuration} properties. Invocations of {@link #getConnection(Configuration)}
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* that pass the same {@link Configuration} instance will return the same
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* {@link HConnection} instance ONLY WHEN the set of properties are the same
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* (i.e. if you change properties in your {@link Configuration} instance, such as RPC timeout,
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* the codec used, HBase will create a new {@link HConnection} instance. For more details on
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* how this is done see {@link HConnectionKey}).
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* <p>Sharing {@link HConnection} instances is usually what you want; all clients
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* of the {@link HConnection} instances share the HConnections' cache of Region
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* locations rather than each having to discover for itself the location of meta, etc.
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* But sharing connections makes clean up of {@link HConnection} instances a little awkward.
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* Currently, clients cleanup by calling {@link #deleteConnection(Configuration)}. This will
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* shutdown the zookeeper connection the HConnection was using and clean up all
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* HConnection resources as well as stopping proxies to servers out on the
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@ -71,15 +65,15 @@ import org.apache.hadoop.hbase.security.User;
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* subsequently used by another will cause breakage so be careful running
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* cleanup.
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* <p>To create a {@link HConnection} that is not shared by others, you can
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* create a new {@link Configuration} instance, pass this new instance to
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* {@link #getConnection(Configuration)}, and then when done, close it up by
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* doing something like the following:
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* set property "hbase.client.instance.id" to a unique value for your {@link Configuration}
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* instance, like the following:
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* <pre>
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* {@code
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* Configuration newConfig = new Configuration(originalConf);
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* HConnection connection = HConnectionManager.getConnection(newConfig);
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* conf.set("hbase.client.instance.id", "12345");
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* HConnection connection = HConnectionManager.getConnection(conf);
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* // Use the connection to your hearts' delight and then when done...
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* HConnectionManager.deleteConnection(newConfig, true);
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* conf.set("hbase.client.instance.id", "12345");
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* HConnectionManager.deleteConnection(conf, true);
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* }
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* </pre>
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* <p>Cleanup used to be done inside in a shutdown hook. On startup we'd
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