snowflake算法由twitter公司出品,原始版本是scala版,用于生成分布式ID,结构图:
算法描述:
- 最高位是符号位,始终为0,不可用。
- 41位的时间序列,精确到毫秒级,41位的长度可以使用69年。时间位还有一个很重要的作用是可以根据时间进行排序。
- 10位的机器标识,10位的长度最多支持部署1024个节点
- 12位的计数序列号,序列号即一系列的自增id,可以支持同一节点同一毫秒生成多个ID序号,12位的计数序列号支持每个节点每毫秒产生4096个ID序号View Code
package com.zhi.idworker.lang; /** * 分布式雪花ID算法 * * @author zhi * @since 2019年5月14日16:51:06 * */ public class SnowFlake { /** * 起始的时间戳 */ private final static long twepoch = 1557825652094L; /** * 每一部分占用的位数 */ private final static long workerIdBits = 5L; private final static long datacenterIdBits = 5L; private final static long sequenceBits = 12L; /** * 每一部分的最大值 */ private final static long maxWorkerId = -1L ^ (-1L << workerIdBits); private final static long maxDatacenterId = -1L ^ (-1L << datacenterIdBits); private final static long maxSequence = -1L ^ (-1L << sequenceBits); /** * 每一部分向左的位移 */ private final static long workerIdShift = sequenceBits; private final static long datacenterIdShift = sequenceBits + workerIdBits; private final static long timestampShift = sequenceBits + workerIdBits + datacenterIdBits; private long datacenterId; // 数据中心ID private long workerId; // 机器ID private long sequence = 0L; // 序列号 private long lastTimestamp = -1L; // 上一次时间戳 public SnowFlake(long workerId, long datacenterId) { if (workerId > maxWorkerId || workerId < 0) { throw new IllegalArgumentException( String.format("worker Id can't be greater than %d or less than 0", maxWorkerId)); } if (datacenterId > maxDatacenterId || datacenterId < 0) { throw new IllegalArgumentException( String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId)); } this.workerId = workerId; this.datacenterId = datacenterId; } public synchronized long nextId() { long timestamp = timeGen(); if (timestamp < lastTimestamp) { throw new RuntimeException(String.format( "Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp)); } if (timestamp == lastTimestamp) { sequence = (sequence + 1) & maxSequence; if (sequence == 0L) { timestamp = tilNextMillis(); } } else { sequence = 0L; } lastTimestamp = timestamp; return (timestamp - twepoch) << timestampShift // 时间戳部分 | datacenterId << datacenterIdShift // 数据中心部分 | workerId << workerIdShift // 机器标识部分 | sequence; // 序列号部分 } private long tilNextMillis() { long timestamp = timeGen(); while (timestamp <= lastTimestamp) { timestamp = timeGen(); } return timestamp; } private long timeGen() { return System.currentTimeMillis(); } }
Java实现:
package com.zhi.idworker; /** * 分布式雪花ID算法 * * @author zhi * @since 2019年5月14日16:51:06 * */ public class SnowFlake { /** * 起始的时间戳 */ private final static long twepoch = 1557825652094L; /** * 每一部分占用的位数 */ private final static long workerIdBits = 5L; private final static long datacenterIdBits = 5L; private final static long sequenceBits = 12L; /** * 每一部分的最大值 */ private final static long maxWorkerId = -1L ^ (-1L << workerIdBits); private final static long maxDatacenterId = -1L ^ (-1L << datacenterIdBits); private final static long maxSequence = -1L ^ (-1L << sequenceBits); /** * 每一部分向左的位移 */ private final static long workerIdShift = sequenceBits; private final static long datacenterIdShift = sequenceBits + workerIdBits; private final static long timestampShift = sequenceBits + workerIdBits + datacenterIdBits; private long datacenterId; // 数据中心ID private long workerId; // 机器ID private long sequence = 0L; // 序列号 private long lastTimestamp = -1L; // 上一次时间戳 public SnowFlake(long workerId, long datacenterId) { if (workerId > maxWorkerId || workerId < 0) { throw new IllegalArgumentException( String.format("worker Id can't be greater than %d or less than 0", maxWorkerId)); } if (datacenterId > maxDatacenterId || datacenterId < 0) { throw new IllegalArgumentException( String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId)); } this.workerId = workerId; this.datacenterId = datacenterId; } public synchronized long nextId() { long timestamp = timeGen(); if (timestamp < lastTimestamp) { throw new RuntimeException(String.format( "Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp)); } if (timestamp == lastTimestamp) { sequence = (sequence + 1) & maxSequence; if (sequence == 0L) { timestamp = tilNextMillis(); } } else { sequence = 0L; } lastTimestamp = timestamp; return (timestamp - twepoch) << timestampShift // 时间戳部分 | datacenterId << datacenterIdShift // 数据中心部分 | workerId << workerIdShift // 机器标识部分 | sequence; // 序列号部分 } private long tilNextMillis() { long timestamp = timeGen(); while (timestamp <= lastTimestamp) { timestamp = timeGen(); } return timestamp; } private long timeGen() { return System.currentTimeMillis(); } }