org.apache.hadoop.hbase.coprocessor.RegionServerCoprocessorEnvironment Maven / Gradle / Ivy
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package org.apache.hadoop.hbase.coprocessor;
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.CoprocessorEnvironment;
import org.apache.hadoop.hbase.HBaseInterfaceAudience;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.client.Connection;
import org.apache.hadoop.hbase.metrics.MetricRegistry;
import org.apache.hadoop.hbase.regionserver.OnlineRegions;
import org.apache.yetus.audience.InterfaceAudience;
import org.apache.yetus.audience.InterfaceStability;
@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
@InterfaceStability.Evolving
public interface RegionServerCoprocessorEnvironment
extends CoprocessorEnvironment {
/** Returns Hosting Server's ServerName */
ServerName getServerName();
/** Returns Interface to Map of regions online on this RegionServer {@link #getServerName()}}. */
OnlineRegions getOnlineRegions();
/**
* Returns the hosts' Connection to the Cluster. Do not close! This is a shared connection with
* the hosting server. Throws {@link UnsupportedOperationException} if you try to close or abort
* it. For light-weight usage only. Heavy-duty usage will pull down the hosting RegionServer
* responsiveness as well as that of other Coprocessors making use of this Connection. Use to
* create table on start or to do administrative operations. Coprocessors should create their own
* Connections if heavy usage to avoid impinging on hosting Server operation. To create a
* Connection or if a Coprocessor requires a region with a particular Configuration, use
* {@link org.apache.hadoop.hbase.client.ConnectionFactory} or
* {@link #createConnection(Configuration)}}.
*
* Be aware that operations that make use of this Connection are executed as the RegionServer
* User, the hbase super user that started this server process. Exercise caution running
* operations as this User (See {@link #createConnection(Configuration)}} to run as other than the
* RegionServer User).
*
* Be careful RPC'ing from a Coprocessor context. RPC's will fail, stall, retry, and/or crawl
* because the remote side is not online, is struggling or it is on the other side of a network
* partition. Any use of Connection from inside a Coprocessor must be able to handle all such
* hiccups.
* @see #createConnection(Configuration)
* @return The host's Connection to the Cluster.
*/
Connection getConnection();
/**
* Creates a cluster connection using the passed Configuration. Creating a Connection is a
* heavy-weight operation. The resultant Connection's cache of region locations will be empty.
* Therefore you should cache and reuse Connections rather than create a Connection on demand.
* Create on start of your Coprocessor. You will have to cast the CoprocessorEnvironment
* appropriately to get at this API at start time because Coprocessor start method is passed a
* subclass of this CoprocessorEnvironment or fetch Connection using a synchronized accessor
* initializing the Connection on first access. Close the returned Connection when done to free
* resources. Using this API rather than
* {@link org.apache.hadoop.hbase.client.ConnectionFactory#createConnection(Configuration)}
* returns a Connection that will short-circuit RPC if the target is a local resource. Use
* ConnectionFactory if you don't need this ability.
*
* Be careful RPC'ing from a Coprocessor context. RPC's will fail, stall, retry, and/or crawl
* because the remote side is not online, is struggling or it is on the other side of a network
* partition. Any use of Connection from inside a Coprocessor must be able to handle all such
* hiccups.
* @return Connection created using the passed conf.
*/
Connection createConnection(Configuration conf) throws IOException;
/**
* Returns a MetricRegistry that can be used to track metrics at the region server level.
*
* See ExampleMasterObserverWithMetrics class in the hbase-examples modules for examples of how
* metrics can be instantiated and used.
*
* @return A MetricRegistry for the coprocessor class to track and export metrics.
*/
MetricRegistry getMetricRegistryForRegionServer();
}