001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018package org.apache.hadoop.hbase.coprocessor; 019 020import java.util.Optional; 021import org.apache.hadoop.hbase.CoprocessorEnvironment; 022import org.apache.hadoop.hbase.HBaseInterfaceAudience; 023import org.apache.hadoop.hbase.security.User; 024import org.apache.yetus.audience.InterfaceAudience; 025import org.apache.yetus.audience.InterfaceStability; 026 027/** 028 * Carries the execution state for a given invocation of an Observer coprocessor 029 * ({@link RegionObserver}, {@link MasterObserver}, or {@link WALObserver}) method. The same 030 * ObserverContext instance is passed sequentially to all loaded coprocessors for a given Observer 031 * method trigger, with the <code>CoprocessorEnvironment</code> reference set appropriately for each 032 * Coprocessor type: e.g. the RegionCoprocessorEnvironment is passed to RegionCoprocessors, and so 033 * on. 034 * @param <E> The {@link CoprocessorEnvironment} subclass applicable to the revelant Observer 035 * interface. 036 */ 037@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC) 038@InterfaceStability.Evolving 039public interface ObserverContext<E extends CoprocessorEnvironment> { 040 E getEnvironment(); 041 042 /** 043 * Call to indicate that the current coprocessor's return value (or parameter -- depends on the 044 * call-type) should be used in place of the value that would be obtained via normal processing; 045 * i.e. bypass the core call and return the Coprocessor's result instead. DOES NOT work for all 046 * Coprocessor invocations, only on a small subset of methods, mostly preXXX calls in 047 * RegionObserver. Check javadoc on the pertinent Coprocessor Observer to see if 048 * <code>bypass</code> is supported. 049 * <p> 050 * This behavior of honoring only a subset of methods is new since hbase-2.0.0. 051 * <p> 052 * Where bypass is supported what is being bypassed is all of the core code implementing the 053 * remainder of the operation. In order to understand what calling bypass() will skip, a 054 * coprocessor implementer should read and understand all of the remaining code and its nuances. 055 * Although this is good practice for coprocessor developers in general, it demands a lot. What is 056 * skipped is extremely version dependent. The core code will vary, perhaps significantly, even 057 * between point releases. We do not provide the promise of consistent behavior even between point 058 * releases for the bypass semantic. To achieve that we could not change any code between hook 059 * points. Therefore the coprocessor implementer becomes an HBase core developer in practice as 060 * soon as they rely on bypass(). Every release of HBase may break the assumption that the 061 * replacement for the bypassed code takes care of all necessary skipped concerns. Because those 062 * concerns can change at any point, such an assumption is never safe. 063 * </p> 064 * <p> 065 * As of hbase2, when bypass has been set, we will NOT call any Coprocessors follow the bypassing 066 * Coprocessor; we cut short the processing and return the bypassing Coprocessors response (this 067 * used be a separate 'complete' option that has been folded into the 'bypass' in hbase2. 068 * </p> 069 */ 070 void bypass(); 071 072 /** 073 * Returns the active user for the coprocessor call. If an explicit {@code User} instance was 074 * provided to the constructor, that will be returned, otherwise if we are in the context of an 075 * RPC call, the remote user is used. May not be present if the execution is outside of an RPC 076 * context. 077 */ 078 Optional<User> getCaller(); 079}