2021-01-22 07:40:02 +00:00
|
|
|
|
package io.github.ehlxr.did.core;
|
2018-08-14 07:21:56 +00:00
|
|
|
|
|
|
|
|
|
/**
|
|
|
|
|
* twitter 的 snowflake 算法 -- java 实现
|
2018-11-16 08:45:17 +00:00
|
|
|
|
* <p>
|
|
|
|
|
* SnowFlake 的优点是,整体上按照时间自增排序,并且整个分布式系统内不会产生 ID 碰撞(由数据中心 ID 和机器 ID 作区分),并且效率较高,经测试,SnowFlake 每秒能够产生 26 万 ID 左右。
|
|
|
|
|
* <p>
|
2018-08-14 07:21:56 +00:00
|
|
|
|
* 协议格式:0 - 0000000000 0000000000 0000000000 0000000000 0 - 00000 - 00000 - 000000000000
|
2018-11-16 08:45:17 +00:00
|
|
|
|
* 协议解释:0 - 41 位时间戳 - 5 位数据中心标识 - 5 位机器标识 - 12 位序列号
|
|
|
|
|
* <p>
|
2021-01-20 07:25:58 +00:00
|
|
|
|
* 1 位标识,由于 Long 基本类型在 Java 中是带符号的,最高位是符号位,正数是 0,负数是 1,所以 id 一般是正数,最高位是 0
|
2018-11-16 08:45:17 +00:00
|
|
|
|
* <p>
|
|
|
|
|
* 41 位时间截(毫秒级),注意,41 位时间截不是存储当前时间的时间截,而是存储时间截的差值(当前时间截 - 开始时间截)得到的值,这里的的开始时间截。
|
|
|
|
|
* 一般是我们的 id 生成器开始使用的时间,由我们程序来指定的(如下下面程序 START_STMP 属性)。41 位的时间截,可以使用 69 年,(1L << 41) / (1000L * 60 * 60 * 24 * 365) = 69
|
|
|
|
|
* <p>
|
|
|
|
|
* 10 位的数据机器位,可以部署在 1024 个节点,包括 5 位数据中心标识,5 位机器标识
|
|
|
|
|
* <p>
|
|
|
|
|
* 12 位序列,毫秒内的计数,12 位的计数顺序号支持每个节点每毫秒(同一机器,同一时间截)产生 4096 个 ID 序号,加起来刚好 64 位,为一个 Long 型。
|
2018-08-14 07:21:56 +00:00
|
|
|
|
*
|
|
|
|
|
* @author ehlxr
|
|
|
|
|
*/
|
|
|
|
|
public class SnowFlake {
|
|
|
|
|
/**
|
|
|
|
|
* 起始的时间戳,可以修改为服务第一次启动的时间
|
|
|
|
|
* 一旦服务已经开始使用,起始时间戳就不能改变
|
2018-11-16 08:45:17 +00:00
|
|
|
|
* <p>
|
2018-08-14 07:21:56 +00:00
|
|
|
|
* 2018/8/14 00:00:00
|
|
|
|
|
*/
|
|
|
|
|
private final static long START_STMP = 1534176000000L;
|
|
|
|
|
|
|
|
|
|
/**
|
|
|
|
|
* 序列号占用的位数
|
|
|
|
|
*/
|
|
|
|
|
private final static long SEQUENCE_BIT = 12;
|
|
|
|
|
/**
|
|
|
|
|
* 机器标识占用的位数
|
|
|
|
|
*/
|
|
|
|
|
private final static long MACHINE_BIT = 5;
|
|
|
|
|
/**
|
|
|
|
|
* 数据中心占用的位数
|
|
|
|
|
*/
|
|
|
|
|
private final static long DATACENTER_BIT = 5;
|
|
|
|
|
|
|
|
|
|
/**
|
|
|
|
|
* 每一部分的最大值
|
|
|
|
|
*/
|
|
|
|
|
private final static long MAX_DATACENTER_NUM = ~(-1L << DATACENTER_BIT);
|
|
|
|
|
private final static long MAX_MACHINE_NUM = ~(-1L << MACHINE_BIT);
|
|
|
|
|
private final static long MAX_SEQUENCE = ~(-1L << SEQUENCE_BIT);
|
|
|
|
|
|
|
|
|
|
/**
|
|
|
|
|
* 每一部分向左的位移
|
|
|
|
|
*/
|
|
|
|
|
private final static long MACHINE_LEFT = SEQUENCE_BIT;
|
|
|
|
|
private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
|
|
|
|
|
private final static long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;
|
|
|
|
|
|
|
|
|
|
/**
|
|
|
|
|
* 数据中心
|
|
|
|
|
*/
|
2021-01-18 08:17:14 +00:00
|
|
|
|
private final long datacenterId;
|
2018-08-14 07:21:56 +00:00
|
|
|
|
/**
|
|
|
|
|
* 机器标识
|
|
|
|
|
*/
|
2021-01-18 08:17:14 +00:00
|
|
|
|
private final long machineId;
|
2018-08-14 07:21:56 +00:00
|
|
|
|
/**
|
|
|
|
|
* 序列号
|
|
|
|
|
*/
|
|
|
|
|
private long sequence = 0L;
|
|
|
|
|
/**
|
|
|
|
|
* 上一次时间戳
|
|
|
|
|
*/
|
|
|
|
|
private long lastStmp = -1L;
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
/**
|
|
|
|
|
* 通过单例模式来获取实例
|
|
|
|
|
* 分布式部署服务时,数据节点标识和机器标识作为联合键必须唯一
|
|
|
|
|
*
|
|
|
|
|
* @param datacenterId 数据节点标识ID
|
|
|
|
|
* @param machineId 机器标识ID
|
|
|
|
|
*/
|
|
|
|
|
public SnowFlake(long datacenterId, long machineId) {
|
|
|
|
|
if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
|
2018-11-16 08:20:23 +00:00
|
|
|
|
throw new IllegalArgumentException("datacenterId can't be greater than " + MAX_DATACENTER_NUM + " or less than 0");
|
2018-08-14 07:21:56 +00:00
|
|
|
|
}
|
|
|
|
|
if (machineId > MAX_MACHINE_NUM || machineId < 0) {
|
2018-11-16 08:20:23 +00:00
|
|
|
|
throw new IllegalArgumentException("machineId can't be greater than " + MAX_MACHINE_NUM + " or less than 0");
|
2018-08-14 07:21:56 +00:00
|
|
|
|
}
|
|
|
|
|
this.datacenterId = datacenterId;
|
|
|
|
|
this.machineId = machineId;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/**
|
|
|
|
|
* 产生下一个ID
|
|
|
|
|
*/
|
|
|
|
|
public synchronized long nextId() {
|
|
|
|
|
long currStmp = getNewstmp();
|
|
|
|
|
if (currStmp < lastStmp) {
|
|
|
|
|
throw new RuntimeException("Clock moved backwards. Refusing to generate id");
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
if (currStmp == lastStmp) {
|
|
|
|
|
//相同毫秒内,序列号自增
|
|
|
|
|
sequence = (sequence + 1) & MAX_SEQUENCE;
|
|
|
|
|
//同一毫秒的序列数已经达到最大
|
|
|
|
|
if (sequence == 0L) {
|
|
|
|
|
currStmp = getNextMill();
|
|
|
|
|
}
|
|
|
|
|
} else {
|
|
|
|
|
//不同毫秒内,序列号置为0
|
|
|
|
|
sequence = 0L;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
lastStmp = currStmp;
|
|
|
|
|
|
|
|
|
|
// 时间戳部分 | 数据中心部分 | 机器标识部分 | 序列号部分
|
|
|
|
|
return (currStmp - START_STMP) << TIMESTMP_LEFT | datacenterId << DATACENTER_LEFT | machineId << MACHINE_LEFT | sequence;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
private long getNextMill() {
|
|
|
|
|
long mill = getNewstmp();
|
|
|
|
|
while (mill <= lastStmp) {
|
|
|
|
|
mill = getNewstmp();
|
|
|
|
|
}
|
|
|
|
|
return mill;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
private long getNewstmp() {
|
|
|
|
|
return System.currentTimeMillis();
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
public static void main(String[] args) {
|
|
|
|
|
SnowFlake snowFlake = new SnowFlake(2, 3);
|
|
|
|
|
long start = System.currentTimeMillis();
|
|
|
|
|
for (int i = 0; i < (1 << 18); i++) {
|
|
|
|
|
System.out.println(i + ": " + snowFlake.nextId());
|
|
|
|
|
}
|
|
|
|
|
long end = System.currentTimeMillis();
|
|
|
|
|
System.out.println(end - start);
|
|
|
|
|
}
|
2021-01-27 03:47:09 +00:00
|
|
|
|
|
|
|
|
|
public static SnowFlakeBuilder newBuilder() {
|
|
|
|
|
return new SnowFlakeBuilder();
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
public static final class SnowFlakeBuilder {
|
|
|
|
|
private long datacenterId;
|
|
|
|
|
private long machineId;
|
|
|
|
|
|
|
|
|
|
private SnowFlakeBuilder() {
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
public SnowFlakeBuilder datacenterId(long datacenterId) {
|
|
|
|
|
this.datacenterId = datacenterId;
|
|
|
|
|
return this;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
public SnowFlakeBuilder machineId(long machineId) {
|
|
|
|
|
this.machineId = machineId;
|
|
|
|
|
return this;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
public SnowFlake build() {
|
|
|
|
|
return new SnowFlake(datacenterId, machineId);
|
|
|
|
|
}
|
|
|
|
|
}
|
2018-08-14 07:21:56 +00:00
|
|
|
|
}
|