com.github.sylphlike.framework.utils.sequence.StandardSequence Maven / Gradle / Ivy
package com.github.sylphlike.framework.utils.sequence;
import com.github.sylphlike.framework.utils.general.Clock;
import java.util.concurrent.ThreadLocalRandom;
/**
*
* time 10/09/2020 18:19 星期四 (dd/MM/YYYY HH:mm)
*
email [email protected]
*
* 0 - 0000000000 0000000000 0000000000 0000000000 0 - 00000 - 00000 - 000000000000
* 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
* 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
* 10位的数据机器位，可以部署在1024个节点，包括5位datacenterId和5位workerId
* 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
*
*
* @author Gopal.pan
* @version 1.0.0
*/
public class StandardSequence {
/** 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 static long TWEPOCH = 1585038908558L;
/** 数据中心标识位数 */
private final static long DATA_CENTER_ID_BITS = 5L;
/** 机器标识位数 */
private final static long WORKER_ID_BITS = 5L;
/** 毫秒内自增位 */
private final static long SEQUENCE_BITS = 12L;
/** 数据中心ID最大值 */
private final static long MAX_DATA_CENTER_ID = 31;
/** 机器ID最大值 */
private final static long MAX_WORKER_ID = 31;
/** 机器ID左移12位 */
private final static long WORKER_ID_SHIFT = SEQUENCE_BITS;
/** 数据中心ID左移17位 */
private final static long DATA_CENTER_ID_SHIFT = WORKER_ID_SHIFT + WORKER_ID_BITS;
/** 时间毫秒左移22位 */
private final static long TIMESTAMP_LEFT_SHIFT = DATA_CENTER_ID_SHIFT + DATA_CENTER_ID_BITS;
private final static long SEQUENCE_MASK = 4095;
/** 上次生产id时间戳 */
private static long lastTimestamp = -1L;
/** 并发控制 */
private long sequence = 0L;
private final long dataCenterId;
private final long workerId;
public StandardSequence() {
this.dataCenterId = MarkProvider.getDataCenterId(MAX_DATA_CENTER_ID);
this.workerId = MarkProvider.getWorkerId(dataCenterId, MAX_WORKER_ID);
}
public StandardSequence(long workerId, long dataCenterId) {
if (workerId > MAX_WORKER_ID || workerId < 0) {
throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", MAX_WORKER_ID));
}
if (dataCenterId > MAX_DATA_CENTER_ID || dataCenterId < 0) {
throw new IllegalArgumentException(String.format("dataCenter Id can't be greater than %d or less than 0", MAX_DATA_CENTER_ID));
}
this.workerId = workerId;
this.dataCenterId = dataCenterId;
}
/**
* 获取下一个ID
*
time 10:43 2021/1/5 (HH:mm yyyy/MM/dd)
*
email [email protected]
* @return long
* @author Gopal.pan
*/
public synchronized long nextId() {
long timestamp = Clock.now();
timeMillisGen(timestamp);
// 41位时间截(毫秒级) << 22 | 5位的数据机器位 << 17 | 5位workerId << 12 |12位序列
return ((timestamp - TWEPOCH) << TIMESTAMP_LEFT_SHIFT)
| (dataCenterId << DATA_CENTER_ID_SHIFT)
| (workerId << WORKER_ID_SHIFT)
| sequence;
}
private long tilNextMillis(final long lastTimestamp) {
long timestamp = Clock.now();
while (timestamp <= lastTimestamp) {
timestamp = Clock.now();
}
return timestamp;
}
private void timeMillisGen(long timestamp) {
if (timestamp < lastTimestamp) {
throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
}
if (lastTimestamp == timestamp) {
// 当前毫秒内，则+1
sequence = (sequence + 1) & SEQUENCE_MASK;
if (sequence == 0) {
// 当前毫秒内计数满了，则等待下一秒
timestamp = tilNextMillis(lastTimestamp);
}
} else {
sequence = ThreadLocalRandom.current().nextLong(0, 32);
}
lastTimestamp = timestamp;
}
}