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/*
* Copyright (c) 2011-2020, hubin (jobob@qq.com).
* <p>
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
* <p>
* http://www.apache.org/licenses/LICENSE-2.0
* <p>
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package io.hmit.utils;
import org.apache.commons.lang.StringUtils;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.util.concurrent.ThreadLocalRandom;
/**
* <p>
* 分布式高效有序ID生产黑科技(sequence) <br>
* 优化开源项目：http://git.oschina.net/yu120/sequence
* </p>
*
* @author hubin
* @since 2016-08-18
*/
public class Sequence {
private static final Log logger = LogFactory.getLog(Sequence.class);
/**
* 时间起始标记点，作为基准，一般取系统的最近时间（一旦确定不能变动）
*/
private final long twepoch = 1288834974657L;
/**
* 机器标识位数
*/
private final long workerIdBits = 5L;
private final long datacenterIdBits = 5L;
private final long maxWorkerId = -1L ^ (-1L << workerIdBits);
private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
/**
* 毫秒内自增位
*/
private final long sequenceBits = 12L;
private final long workerIdShift = sequenceBits;
private final long datacenterIdShift = sequenceBits + workerIdBits;
/**
* 时间戳左移动位
*/
private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
private final long sequenceMask = -1L ^ (-1L << sequenceBits);
private final long workerId;
/**
* 数据标识 ID 部分
*/
private final long datacenterId;
/**
* 并发控制
*/
private long sequence = 0L;
/**
* 上次生产 ID 时间戳
*/
private long lastTimestamp = -1L;
public Sequence() {
this.datacenterId = getDatacenterId(maxDatacenterId);
this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
}
/**
* <p>
* 有参构造器
* </p>
*
* @param workerId 工作机器 ID
* @param datacenterId 序列号
*/
public Sequence(long workerId, long datacenterId) {
Assert.isFalse(workerId > maxWorkerId || workerId < 0,
String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
Assert.isFalse(datacenterId > maxDatacenterId || datacenterId < 0,
String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
this.workerId = workerId;
this.datacenterId = datacenterId;
}
/**
* <p>
* 获取 maxWorkerId
* </p>
*/
protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {
StringBuilder mpid = new StringBuilder();
mpid.append(datacenterId);
String name = ManagementFactory.getRuntimeMXBean().getName();
if (StringUtils.isNotEmpty(name)) {
/*
* GET jvmPid
*/
mpid.append(name.split(StringPool.AT)[0]);
}
/*
* MAC + PID 的 hashcode 获取16个低位
*/
return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
}
/**
* <p>
* 数据标识id部分
* </p>
*/
protected static long getDatacenterId(long maxDatacenterId) {
long id = 0L;
try {
InetAddress ip = InetAddress.getLocalHost();
NetworkInterface network = NetworkInterface.getByInetAddress(ip);
if (network == null) {
id = 1L;
} else {
byte[] mac = network.getHardwareAddress();
if (null != mac) {
id = ((0x000000FF & (long) mac[mac.length - 1]) | (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
id = id % (maxDatacenterId + 1);
}
}
} catch (Exception e) {
logger.warn(" getDatacenterId: " + e.getMessage());
}
return id;
}
/**
* 获取下一个ID
*
* @return
*/
public synchronized long nextId() {
long timestamp = timeGen();
//闰秒
if (timestamp < lastTimestamp) {
long offset = lastTimestamp - timestamp;
if (offset <= 5) {
try {
wait(offset << 1);
timestamp = timeGen();
if (timestamp < lastTimestamp) {
throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", offset));
}
} catch (Exception e) {
throw new RuntimeException(e);
}
} else {
throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", offset));
}
}
if (lastTimestamp == timestamp) {
// 相同毫秒内，序列号自增
sequence = (sequence + 1) & sequenceMask;
if (sequence == 0) {
// 同一毫秒的序列数已经达到最大
timestamp = tilNextMillis(lastTimestamp);
}
} else {
// 不同毫秒内，序列号置为 1 - 3 随机数
sequence = ThreadLocalRandom.current().nextLong(1, 3);
}
lastTimestamp = timestamp;
// 时间戳部分 | 数据中心部分 | 机器标识部分 | 序列号部分
return ((timestamp - twepoch) << timestampLeftShift)
| (datacenterId << datacenterIdShift)
| (workerId << workerIdShift)
| sequence;
}
protected long tilNextMillis(long lastTimestamp) {
long timestamp = timeGen();
while (timestamp <= lastTimestamp) {
timestamp = timeGen();
}
return timestamp;
}
protected long timeGen() {
return SystemClock.now();
}
}