import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.util.Date;
import java.util.concurrent.ThreadLocalRandom;
/**
* @author NiaoGe
* <p>
* 雪花算法生成唯一 id,参考开源项目：
* https://gitee.com/yu120/sequence
* https://apidoc.gitee.com/loolly/hutool/cn/hutool/core/util/IdUtil.html
* </p>
*/
public class IdGenerator {
private static final Logger logger = LoggerFactory.getLogger(IdGenerator.class);
//工作机器 id
private long workerId;
//数据中心 id
private long datacenterId;
//序列号
private long sequence = 0L;
//基准时间，一般取系统的最近时间（一旦确定不能变动）
private long twepoch;
private long workerIdBits;
private long datacenterIdBits;
private long maxWorkerId;
private long maxDatacenterId;
//毫秒内自增位数
private long sequenceBits;
//位与运算保证毫秒内 Id 范围
private long sequenceMask;
//工作机器 id 需要左移的位数
private long workerIdShift;
//数据中心 id 需要左移位数
private long datacenterIdShift;
//时间戳需要左移位数
private long timestampLeftShift;
//上次生成 id 的时间戳，初始值为负数
private long lastTimestamp = -1L;
//true 表示毫秒内初始序列采用随机值
private boolean randomSequence;
//随机初始序列计数器
private long count = 0L;
//允许时钟回拨的毫秒数
private long timeOffset;
private final ThreadLocalRandom tlr = ThreadLocalRandom.current();
/**
* 无参构造器，自动生成 workerId/datacenterId
*/
public IdGenerator() {
this(false, 10, null, 5L, 5L, 12L);
}
/**
* 有参构造器,调用者自行保证数据中心 ID+机器 ID 的唯一性
* 标准 snowflake 实现
*
* @param workerId 工作机器 ID
* @param datacenterId 数据中心 ID
*/
public IdGenerator(long workerId, long datacenterId) {
this(workerId, datacenterId, false, 10, null, 5L, 5L, 12L);
}
/**
* @param randomSequence true 表示每毫秒内起始序号使用随机值
* @param timeOffset 允许时间回拨的毫秒数
* @param epochDate 基准时间
* @param workerIdBits workerId 位数
* @param datacenterIdBits datacenterId 位数
* @param sequenceBits sequence 位数
*/
public IdGenerator(boolean randomSequence, long timeOffset, Date epochDate, long workerIdBits, long datacenterIdBits, long sequenceBits) {
if (null != epochDate) {
this.twepoch = epochDate.getTime();
} else {
// 2012/12/12 23:59:59 GMT
this.twepoch = 1355327999000L;
}
this.workerIdBits = workerIdBits;
this.datacenterIdBits = datacenterIdBits;
this.maxWorkerId = -1L ^ (-1L << workerIdBits);
this.maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
this.sequenceBits = sequenceBits;
this.sequenceMask = -1L ^ (-1L << sequenceBits);
this.workerIdShift = sequenceBits;
this.datacenterIdShift = sequenceBits + workerIdBits;
this.timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
this.datacenterId = getDatacenterId(maxDatacenterId);
this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
this.randomSequence = randomSequence;
this.timeOffset = timeOffset;
String initialInfo = String.format("worker starting. timestamp left shift %d, datacenter id bits %d, worker id bits %d, sequence bits %d, datacenterid %d, workerid %d",
timestampLeftShift, datacenterIdBits, workerIdBits, sequenceBits, datacenterId, workerId);
logger.info(initialInfo);
}
/**
* 自定义 workerId+datacenterId+其它初始配置
* 调整 workerId、datacenterId、sequence 位数定制雪花算法,控制生成的 Id 的位数
*
* @param workerId 工作机器 ID
* @param datacenterId 数据中心 ID
* @param randomSequence true 表示每毫秒内起始序号使用随机值
* @param timeOffset 允许时间回拨的毫秒数
* @param epochDate 基准时间
* @param workerIdBits workerId 位数
* @param datacenterIdBits datacenterId 位数
* @param sequenceBits sequence 位数
*/
public IdGenerator(long workerId, long datacenterId, boolean randomSequence, long timeOffset, Date epochDate, long workerIdBits, long datacenterIdBits, long sequenceBits) {
this.workerIdBits = workerIdBits;
this.datacenterIdBits = datacenterIdBits;
this.maxWorkerId = -1L ^ (-1L << workerIdBits);
this.maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
if (workerId > maxWorkerId || workerId < 0) {
throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0\r\n", maxWorkerId));
}
if (datacenterId > maxDatacenterId || datacenterId < 0) {
throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0\r\n", maxDatacenterId));
}
if (null != epochDate) {
this.twepoch = epochDate.getTime();
} else {
// 2012/12/12 23:59:59 GMT
this.twepoch = 1355327999000L;
}
this.sequenceBits = sequenceBits;
this.sequenceMask = -1L ^ (-1L << sequenceBits);
this.workerIdShift = sequenceBits;
this.datacenterIdShift = sequenceBits + workerIdBits;
this.timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
this.workerId = workerId;
this.datacenterId = datacenterId;
this.timeOffset = timeOffset;
this.randomSequence = randomSequence;
String initialInfo = String.format("worker starting. timestamp left shift %d, datacenter id bits %d, worker id bits %d, sequence bits %d, datacenterid %d, workerid %d",
timestampLeftShift, datacenterIdBits, workerIdBits, sequenceBits, datacenterId, workerId);
logger.info(initialInfo);
}
private 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) {
throw new RuntimeException("GetDatacenterId Exception", e);
}
return id;
}
private static long getMaxWorkerId(long datacenterId, long maxWorkerId) {
StringBuilder macIpPid = new StringBuilder();
macIpPid.append(datacenterId);
try {
String name = ManagementFactory.getRuntimeMXBean().getName();
if (name != null && !name.isEmpty()) {
//GET jvmPid
macIpPid.append(name.split("@")[0]);
}
//GET hostIpAddress
String hostIp = InetAddress.getLocalHost().getHostAddress();
String ipStr = hostIp.replaceAll("\\.", "");
macIpPid.append(ipStr);
} catch (Exception e) {
throw new RuntimeException("GetMaxWorkerId Exception", e);
}
//MAC + PID + IP 的 hashcode 取低 16 位
return (macIpPid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
}
public synchronized long nextId() {
long currentTimestamp = timeGen();
//获取当前时间戳如果小于上次时间戳，则表示时间戳获取出现异常
if (currentTimestamp < lastTimestamp) {
// 校验时间偏移回拨量
long offset = lastTimestamp - currentTimestamp;
if (offset > timeOffset) {
throw new RuntimeException("Clock moved backwards, refusing to generate id for [" + offset + "ms]");
}
try {
// 时间回退 timeOffset 毫秒内，则允许等待 2 倍的偏移量后重新获取，解决小范围的时间回拨问题
this.wait(offset << 1);
} catch (Exception e) {
throw new RuntimeException(e);
}
currentTimestamp = timeGen();
if (currentTimestamp < lastTimestamp) {
throw new RuntimeException("Clock moved backwards, refusing to generate id for [" + offset + "ms]");
}
}
//如果获取的当前时间戳等于上次时间戳（即同一毫秒内），则序列号自增
if (lastTimestamp == currentTimestamp) {
// randomSequence 为 true 表示随机生成允许范围内的起始序列,否则毫秒内起始值从 0L 开始自增
long tempSequence = sequence + 1;
if (randomSequence) {
sequence = tempSequence & sequenceMask;
count = (count + 1) & sequenceMask;
if (count == 0) {
currentTimestamp = this.tillNextMillis(lastTimestamp);
}
} else {
sequence = tempSequence & sequenceMask;
if (sequence == 0) {
currentTimestamp = this.tillNextMillis(lastTimestamp);
}
}
} else {
sequence = randomSequence ? tlr.nextLong(sequenceMask + 1) : 0L;
count = 0L;
}
lastTimestamp = currentTimestamp;
return ((currentTimestamp - twepoch) << timestampLeftShift) |
(datacenterId << datacenterIdShift) |
(workerId << workerIdShift) |
sequence;
}
private long tillNextMillis(long lastTimestamp) {
long timestamp = timeGen();
while (timestamp <= lastTimestamp) {
timestamp = timeGen();
}
return timestamp;
}
private long timeGen() {
return System.currentTimeMillis();
}
/**
* 测试
* @param args
*/
public static void main(String[] args) {
// for (int i = 0; i < 10; i++) {
// IdGenerator idGenerator = new IdGenerator();
// new Thread(() -> {
// for (int j = 0; j < 100; j++) {
// System.out.println(idGenerator.nextId());
// }
// }).start();
// }
// IdGenerator idGenerator = new IdGenerator(1, 1);
// for (int j = 0; j < 2000; j++) {
// System.out.println(System.currentTimeMillis() + " " + idGenerator.nextId());
// }
// IdGenerator idGenerator = new IdGenerator(true, 10, null, 3L, 2L, 7L);
// for (int j = 0; j < 2000; j++) {
// System.out.println(System.currentTimeMillis() + " " + idGenerator.nextId());
// }
IdGenerator shortIdGenerator = new IdGenerator(7, 3, true, 10, null, 3, 2, 7);
for (int j = 0; j < 1000; j++) {
System.out.println(System.currentTimeMillis() + " " + shortIdGenerator.nextId());
}
}
}
