分布式ID神器之雪花算法简介 - 知乎 (zhihu.com)
java实现
public class SnowflakeIdWorker {
/**
* 开始时间截 (2015-01-01)
*/
private final long twepoch = 1420041600000L;
/**
* 机器id所占的位数
*/
private final long workerIdBits = 5L;
/**
* 数据标识id所占的位数
*/
private final long datacenterIdBits = 5L;
/**
* 支持的最大机器id，结果是31 (这个移位算法可以很快的计算出几位二进制数所能表示的最大十进制数)
*/
private final long maxWorkerId = -1L ^ (-1L << workerIdBits);
/**
* 支持的最大数据标识id，结果是31
*/
private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
/**
* 序列在id中占的位数
*/
private final long sequenceBits = 12L;
/**
* 机器ID向左移12位
*/
private final long workerIdShift = sequenceBits;
/**
* 数据标识id向左移17位(12+5)
*/
private final long datacenterIdShift = sequenceBits + workerIdBits;
/**
* 时间截向左移22位(5+5+12)
*/
private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
/**
* 生成序列的掩码，这里为4095 (0b111111111111=0xfff=4095)
*/
private final long sequenceMask = -1L ^ (-1L << sequenceBits);
/**
* 工作机器ID(0~31)
*/
private long workerId;
/**
* 数据中心ID(0~31)
*/
private long datacenterId;
/**
* 毫秒内序列(0~4095)
*/
private long sequence = 0L;
/**
* 上次生成ID的时间截
*/
private long lastTimestamp = -1L;
/**
* 构造函数
* @param workerId 工作ID (0~31)
* @param datacenterId 数据中心ID (0~31)
*/
public SnowflakeIdWorker(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;
}
/**
* 获得下一个ID (该方法是线程安全的)
* @return SnowflakeId
*/
public synchronized long nextId() {
long timestamp = timeGen();
// 如果当前时间小于上一次ID生成的时间戳，说明系统时钟回退过这个时候应当抛出异常
if (timestamp < lastTimestamp) {
throw new RuntimeException(
String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
}
// 如果是同一时间生成的，则进行毫秒内序列
if (lastTimestamp == timestamp) {
sequence = (sequence + 1) & sequenceMask;
// 毫秒内序列溢出
if (sequence == 0) {
//阻塞到下一个毫秒,获得新的时间戳
timestamp = tilNextMillis(lastTimestamp);
}
}
// 时间戳改变，毫秒内序列重置
else {
sequence = 0L;
}
// 上次生成ID的时间截
lastTimestamp = timestamp;
// 移位并通过或运算拼到一起组成64位的ID
return ((timestamp - twepoch) << timestampLeftShift) //
| (datacenterId << datacenterIdShift) //
| (workerId << workerIdShift) //
| sequence;
}
/**
* 阻塞到下一个毫秒，直到获得新的时间戳
* @param lastTimestamp 上次生成ID的时间截
* @return 当前时间戳
*/
protected long tilNextMillis(long lastTimestamp) {
long timestamp = timeGen();
while (timestamp <= lastTimestamp) {
timestamp = timeGen();
}
return timestamp;
}
/**
* 返回以毫秒为单位的当前时间
* @return 当前时间(毫秒)
*/
protected long timeGen() {
return System.currentTimeMillis();
}
public static void main(String[] args) throws InterruptedException {
SnowflakeIdWorker idWorker = new SnowflakeIdWorker(0, 0);
for (int i = 0; i < 10; i++) {
long id = idWorker.nextId();
Thread.sleep(1);
System.out.println(id);
}
}
}
Python实现
import time
class InvalidSystemClock(Exception):
"""
时钟回拨异常
"""
pass
# 64位ID的划分
WORKER_ID_BITS = 5
DATACENTER_ID_BITS = 5
SEQUENCE_BITS = 12
# 最大取值计算
MAX_WORKER_ID = -1 ^ (-1 << WORKER_ID_BITS) # 2**5-1 0b11111
MAX_DATACENTER_ID = -1 ^ (-1 << DATACENTER_ID_BITS)
# 移位偏移计算
WOKER_ID_SHIFT = SEQUENCE_BITS
DATACENTER_ID_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS
TIMESTAMP_LEFT_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS + DATACENTER_ID_BITS
# 序号循环掩码
SEQUENCE_MASK = -1 ^ (-1 << SEQUENCE_BITS)
# 开始时间截 (2015-01-01)
TWEPOCH = 1420041600000
class IdWorker(object):
"""
用于生成IDs
"""
def __init__(self, datacenter_id, worker_id, sequence=0):
"""
初始化
:param datacenter_id: 数据中心（机器区域）ID
:param worker_id: 机器ID
:param sequence: 其实序号
"""
# sanity check
if worker_id > MAX_WORKER_ID or worker_id < 0:
raise ValueError('worker_id值越界')
if datacenter_id > MAX_DATACENTER_ID or datacenter_id < 0:
raise ValueError('datacenter_id值越界')
self.worker_id = worker_id
self.datacenter_id = datacenter_id
self.sequence = sequence
self.last_timestamp = -1 # 上次计算的时间戳
def _gen_timestamp(self):
"""
生成整数时间戳
:return:int timestamp
"""
return int(time.time() * 1000)
def get_id(self):
"""
获取新ID
:return:
"""
timestamp = self._gen_timestamp()
# 时钟回拨
if timestamp < self.last_timestamp:
raise InvalidSystemClock
if timestamp == self.last_timestamp:
self.sequence = (self.sequence + 1) & SEQUENCE_MASK
if self.sequence == 0:
timestamp = self._til_next_millis(self.last_timestamp)
else:
self.sequence = 0
self.last_timestamp = timestamp
new_id = ((timestamp - TWEPOCH) << TIMESTAMP_LEFT_SHIFT) | (self.datacenter_id << DATACENTER_ID_SHIFT) | \
(self.worker_id << WOKER_ID_SHIFT) | self.sequence
return new_id
def _til_next_millis(self, last_timestamp):
"""
等到下一毫秒
"""
timestamp = self._gen_timestamp()
while timestamp <= last_timestamp:
timestamp = self._gen_timestamp()
return timestamp
if __name__ == '__main__':
worker = IdWorker(0, 0)
print(worker.get_id())
```
```
