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.hbase.KeyValue; 27 import org.apache.hadoop.hbase.client.Durability; 28 import org.apache.hadoop.hbase.regionserver.wal.WALEdit; 29 30 import com.google.protobuf.Message; 31 32 @InterfaceAudience.Private 33 34 /** 35 * Defines the procedure to atomically perform multiple scans and mutations 36 * on a HRegion. 37 * 38 * This is invoked by HRegion#processRowsWithLocks(). 39 * This class performs scans and generates mutations and WAL edits. 40 * The locks and MVCC will be handled by HRegion. 41 * 42 * The RowProcessor user code could have data that needs to be 43 * sent across for proper initialization at the server side. The generic type 44 * parameter S is the type of the request data sent to the server. 45 * The generic type parameter T is the return type of RowProcessor.getResult(). 46 */ 47 public interface RowProcessor<S extends Message, T extends Message> { 48 49 /** 50 * Rows to lock while operation. 51 * They have to be sorted with <code>RowProcessor</code> 52 * to avoid deadlock. 53 */ 54 Collection<byte[]> getRowsToLock(); 55 56 /** 57 * Obtain the processing result. All row processor implementations must 58 * implement this, even if the method is simply returning an empty 59 * Message. 60 */ 61 T getResult(); 62 63 /** 64 * Is this operation read only? If this is true, process() should not add 65 * any mutations or it throws IOException. 66 * @return ture if read only operation 67 */ 68 boolean readOnly(); 69 70 /** 71 * HRegion handles the locks and MVCC and invokes this method properly. 72 * 73 * You should override this to create your own RowProcessor. 74 * 75 * If you are doing read-modify-write here, you should consider using 76 * <code>IsolationLevel.READ_UNCOMMITTED</code> for scan because 77 * we advance MVCC after releasing the locks for optimization purpose. 78 * 79 * @param now the current system millisecond 80 * @param region the HRegion 81 * @param mutations the output mutations to apply to memstore 82 * @param walEdit the output WAL edits to apply to write ahead log 83 */ 84 void process(long now, 85 HRegion region, 86 List<KeyValue> mutations, 87 WALEdit walEdit) throws IOException; 88 89 /** 90 * The hook to be executed before process(). 91 * 92 * @param region the HRegion 93 * @param walEdit the output WAL edits to apply to write ahead log 94 */ 95 void preProcess(HRegion region, WALEdit walEdit) throws IOException; 96 97 /** 98 * The hook to be executed after process(). 99 * 100 * @param region the HRegion 101 * @param walEdit the output WAL edits to apply to write ahead log 102 */ 103 void postProcess(HRegion region, WALEdit walEdit) throws IOException; 104 105 106 /** 107 * @return The cluster ids that have the change. 108 */ 109 List<UUID> getClusterIds(); 110 111 /** 112 * Human readable name of the processor 113 * @return The name of the processor 114 */ 115 String getName(); 116 117 /** 118 * This method should return any additional data that is needed on the 119 * server side to construct the RowProcessor. The server will pass this to 120 * the {@link #initialize(Message msg)} method. If there is no RowProcessor 121 * specific data then null should be returned. 122 * @return the PB message 123 * @throws IOException 124 */ 125 S getRequestData() throws IOException; 126 127 /** 128 * This method should initialize any field(s) of the RowProcessor with 129 * a parsing of the passed message bytes (used on the server side). 130 * @param msg 131 * @throws IOException 132 */ 133 void initialize(S msg) throws IOException; 134 135 /** 136 * @return The {@link Durability} to use 137 */ 138 Durability useDurability(); 139 }