001/**
002 *
003 * Licensed to the Apache Software Foundation (ASF) under one
004 * or more contributor license agreements.  See the NOTICE file
005 * distributed with this work for additional information
006 * regarding copyright ownership.  The ASF licenses this file
007 * to you under the Apache License, Version 2.0 (the
008 * "License"); you may not use this file except in compliance
009 * with the License.  You may obtain a copy of the License at
010 *
011 *     http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS,
015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 */
019package org.apache.hadoop.hbase.regionserver;
020
021import org.apache.hbase.thirdparty.com.google.common.hash.Hashing;
022
023import java.util.concurrent.atomic.AtomicInteger;
024
025import org.apache.hadoop.hbase.ServerName;
026import org.apache.yetus.audience.InterfaceAudience;
027
028/**
029 * Generate a new style scanner id to prevent collision with previous started server or other RSs.
030 * We have 64 bits to use.
031 * The first 32 bits are MurmurHash32 of ServerName string "host,port,ts".
032 * The ServerName contains both host, port, and start timestamp so it can prevent collision.
033 * The lowest 32bit is generated by atomic int.
034 */
035@InterfaceAudience.Private
036public class ScannerIdGenerator {
037
038  private final long serverNameHash;
039  private final AtomicInteger scannerIdGen = new AtomicInteger(0);
040
041  public ScannerIdGenerator(ServerName serverName) {
042    long hash = Hashing.murmur3_32().hashString(serverName.toString(),
043        java.nio.charset.StandardCharsets.UTF_8).asInt();
044    this.serverNameHash = hash << 32;
045  }
046
047  public long generateNewScannerId() {
048    return (scannerIdGen.incrementAndGet() & 0x00000000FFFFFFFFL) | serverNameHash;
049  }
050
051  public static void main(final String [] args) {
052    ScannerIdGenerator sig = new ScannerIdGenerator(ServerName.valueOf("a.example.org,1234,5678"));
053    for (int i = 0; i < 10; i++) {
054      System.out.println(sig.generateNewScannerId());
055    }
056  }
057}