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.regionserver; 019 020import java.util.concurrent.atomic.AtomicInteger; 021import org.apache.hadoop.hbase.ServerName; 022import org.apache.yetus.audience.InterfaceAudience; 023 024import org.apache.hbase.thirdparty.com.google.common.hash.Hashing; 025 026/** 027 * Generate a new style scanner id to prevent collision with previous started server or other RSs. 028 * We have 64 bits to use. The first 32 bits are MurmurHash32 of ServerName string "host,port,ts". 029 * The ServerName contains both host, port, and start timestamp so it can prevent collision. The 030 * lowest 32bit is generated by atomic int. 031 */ 032@InterfaceAudience.Private 033public class ScannerIdGenerator { 034 035 private final long serverNameHash; 036 private final AtomicInteger scannerIdGen = new AtomicInteger(0); 037 038 public ScannerIdGenerator(ServerName serverName) { 039 long hash = Hashing.murmur3_32() 040 .hashString(serverName.toString(), java.nio.charset.StandardCharsets.UTF_8).asInt(); 041 this.serverNameHash = hash << 32; 042 } 043 044 public long generateNewScannerId() { 045 return (scannerIdGen.incrementAndGet() & 0x00000000FFFFFFFFL) | serverNameHash; 046 } 047 048 public static void main(final String[] args) { 049 ScannerIdGenerator sig = new ScannerIdGenerator(ServerName.valueOf("a.example.org,1234,5678")); 050 for (int i = 0; i < 10; i++) { 051 System.out.println(sig.generateNewScannerId()); 052 } 053 } 054}