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/*
* Licensed to the Apache Software Foundation (ASF) under one
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* distributed with this work for additional information
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* 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,
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* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hbase.coprocessor;
import java.util.Optional;
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;
/**
* 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();
}