org.apache.hadoop.hbase.Coprocessor Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hbase;
import com.google.protobuf.Service;
import java.io.IOException;
import java.util.Collections;
import org.apache.yetus.audience.InterfaceAudience;
import org.apache.yetus.audience.InterfaceStability;
/**
* Base interface for the 4 coprocessors - MasterCoprocessor, RegionCoprocessor,
* RegionServerCoprocessor, and WALCoprocessor. Do NOT implement this interface directly. Unless an
* implementation implements one (or more) of the above mentioned 4 coprocessors, it'll fail to be
* loaded by any coprocessor host. Example: Building a coprocessor to observe Master operations.
*
*
* class MyMasterCoprocessor implements MasterCoprocessor {
* @Override
* public Optional<MasterObserver> getMasterObserver() {
* return new MyMasterObserver();
* }
* }
*
* class MyMasterObserver implements MasterObserver {
* ....
* }
*
*
* Building a Service which can be loaded by both Master and RegionServer
*
*
* class MyCoprocessorService implements MasterCoprocessor, RegionServerCoprocessor {
* @Override
* public Optional<Service> getServices() {
* return new ...;
* }
* }
*
*/
@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
@InterfaceStability.Evolving
public interface Coprocessor {
int VERSION = 1;
/** Highest installation priority */
int PRIORITY_HIGHEST = 0;
/** High (system) installation priority */
int PRIORITY_SYSTEM = Integer.MAX_VALUE / 4;
/** Default installation priority for user coprocessors */
int PRIORITY_USER = Integer.MAX_VALUE / 2;
/** Lowest installation priority */
int PRIORITY_LOWEST = Integer.MAX_VALUE;
/**
* Lifecycle state of a given coprocessor instance.
*/
enum State {
UNINSTALLED,
INSTALLED,
STARTING,
ACTIVE,
STOPPING,
STOPPED
}
/**
* Called by the {@link CoprocessorEnvironment} during it's own startup to initialize the
* coprocessor.
*/
default void start(CoprocessorEnvironment env) throws IOException {
}
/**
* Called by the {@link CoprocessorEnvironment} during it's own shutdown to stop the coprocessor.
*/
default void stop(CoprocessorEnvironment env) throws IOException {
}
/**
* Coprocessor endpoints providing protobuf services should override this method.
* @return Iterable of {@link Service}s or empty collection. Implementations should never return
* null.
*/
default Iterable getServices() {
return Collections.EMPTY_SET;
}
}