1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 package org.apache.hadoop.hbase.regionserver; 19 20 import java.io.IOException; 21 import java.util.Collection; 22 import java.util.List; 23 import java.util.UUID; 24 25 import org.apache.hadoop.classification.InterfaceAudience; 26 import org.apache.hadoop.classification.InterfaceStability; 27 import org.apache.hadoop.hbase.KeyValue; 28 import org.apache.hadoop.hbase.client.Durability; 29 import org.apache.hadoop.hbase.regionserver.wal.WALEdit; 30 31 import com.google.protobuf.ByteString; 32 import com.google.protobuf.Message; 33 34 @InterfaceAudience.Public 35 @InterfaceStability.Evolving 36 37 /** 38 * Defines the procedure to atomically perform multiple scans and mutations 39 * on a HRegion. 40 * 41 * This is invoked by HRegion#processRowsWithLocks(). 42 * This class performs scans and generates mutations and WAL edits. 43 * The locks and MVCC will be handled by HRegion. 44 * 45 * The RowProcessor user code could have data that needs to be 46 * sent across for proper initialization at the server side. The generic type 47 * parameter S is the type of the request data sent to the server. 48 * The generic type parameter T is the return type of RowProcessor.getResult(). 49 */ 50 public interface RowProcessor<S extends Message, T extends Message> { 51 52 /** 53 * Rows to lock while operation. 54 * They have to be sorted with <code>RowProcessor</code> 55 * to avoid deadlock. 56 */ 57 Collection<byte[]> getRowsToLock(); 58 59 /** 60 * Obtain the processing result. All row processor implementations must 61 * implement this, even if the method is simply returning an empty 62 * Message. 63 */ 64 T getResult(); 65 66 /** 67 * Is this operation read only? If this is true, process() should not add 68 * any mutations or it throws IOException. 69 * @return ture if read only operation 70 */ 71 boolean readOnly(); 72 73 /** 74 * HRegion handles the locks and MVCC and invokes this method properly. 75 * 76 * You should override this to create your own RowProcessor. 77 * 78 * If you are doing read-modify-write here, you should consider using 79 * <code>IsolationLevel.READ_UNCOMMITTED</code> for scan because 80 * we advance MVCC after releasing the locks for optimization purpose. 81 * 82 * @param now the current system millisecond 83 * @param region the HRegion 84 * @param mutations the output mutations to apply to memstore 85 * @param walEdit the output WAL edits to apply to write ahead log 86 */ 87 void process(long now, 88 HRegion region, 89 List<KeyValue> mutations, 90 WALEdit walEdit) throws IOException; 91 92 /** 93 * The hook to be executed before process(). 94 * 95 * @param region the HRegion 96 * @param walEdit the output WAL edits to apply to write ahead log 97 */ 98 void preProcess(HRegion region, WALEdit walEdit) throws IOException; 99 100 /** 101 * The hook to be executed after process(). 102 * 103 * @param region the HRegion 104 * @param walEdit the output WAL edits to apply to write ahead log 105 */ 106 void postProcess(HRegion region, WALEdit walEdit) throws IOException; 107 108 109 /** 110 * @return The replication cluster id. 111 */ 112 UUID getClusterId(); 113 114 /** 115 * Human readable name of the processor 116 * @return The name of the processor 117 */ 118 String getName(); 119 120 /** 121 * This method should return any additional data that is needed on the 122 * server side to construct the RowProcessor. The server will pass this to 123 * the {@link #initialize(Message msg)} method. If there is no RowProcessor 124 * specific data then null should be returned. 125 * @return the PB message 126 * @throws IOException 127 */ 128 S getRequestData() throws IOException; 129 130 /** 131 * This method should initialize any field(s) of the RowProcessor with 132 * a parsing of the passed message bytes (used on the server side). 133 * @param msg 134 * @throws IOException 135 */ 136 void initialize(S msg) throws IOException; 137 138 /** 139 * @return The {@link Durability} to use 140 */ 141 Durability useDurability(); 142 }