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