org.apache.hadoop.hbase.coprocessor.ObserverContext Maven / Gradle / Ivy
Show all versions of hbase-server Show documentation
/*
* 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.coprocessor;
import org.apache.hadoop.hbase.CoprocessorEnvironment;
import org.apache.hadoop.hbase.HBaseInterfaceAudience;
import org.apache.hadoop.hbase.security.User;
import org.apache.yetus.audience.InterfaceAudience;
import org.apache.yetus.audience.InterfaceStability;
import java.util.Optional;
/**
* Carries the execution state for a given invocation of an Observer coprocessor
* ({@link RegionObserver}, {@link MasterObserver}, or {@link WALObserver})
* method. The same ObserverContext instance is passed sequentially to all loaded
* coprocessors for a given Observer method trigger, with the
* CoprocessorEnvironment reference set appropriately for each Coprocessor type:
* e.g. the RegionCoprocessorEnvironment is passed to RegionCoprocessors, and so on.
* @param The {@link CoprocessorEnvironment} subclass applicable to the
* revelant Observer interface.
*/
@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
@InterfaceStability.Evolving
public interface ObserverContext {
E getEnvironment();
/**
* Call to indicate that the current coprocessor's return value (or parameter -- depends on the
* call-type) should be used in place of the value that would be obtained via normal processing;
* i.e. bypass the core call and return the Coprocessor's result instead. DOES NOT work for all
* Coprocessor invocations, only on a small subset of methods, mostly preXXX calls in
* RegionObserver. Check javadoc on the pertinent Coprocessor Observer to see if
* bypass is supported.
* This behavior of honoring only a subset of methods is new since hbase-2.0.0.
*
Where bypass is supported what is being bypassed is all of the core code
* implementing the remainder of the operation. In order to understand what
* calling bypass() will skip, a coprocessor implementer should read and
* understand all of the remaining code and its nuances. Although this
* is good practice for coprocessor developers in general, it demands a lot.
* What is skipped is extremely version dependent. The core code will vary, perhaps significantly,
* even between point releases. We do not provide the promise of consistent behavior even between
* point releases for the bypass semantic. To achieve
* that we could not change any code between hook points. Therefore the
* coprocessor implementer becomes an HBase core developer in practice as soon
* as they rely on bypass(). Every release of HBase may break the assumption
* that the replacement for the bypassed code takes care of all necessary
* skipped concerns. Because those concerns can change at any point, such an
* assumption is never safe.
* As of hbase2, when bypass has been set, we will NOT call any Coprocessors follow the
* bypassing Coprocessor; we cut short the processing and return the bypassing Coprocessors
* response (this used be a separate 'complete' option that has been folded into the
* 'bypass' in hbase2.
*/
void bypass();
/**
* Returns the active user for the coprocessor call. If an explicit {@code User} instance was
* provided to the constructor, that will be returned, otherwise if we are in the context of an
* RPC call, the remote user is used. May not be present if the execution is outside of an RPC
* context.
*/
Optional getCaller();
}