snowflake是Twitter開源的分布式ID生成算法帐要，結(jié)果是一個(gè)long型的ID把敞。其核心思想是：使用41bit作為毫秒數(shù)，10bit作為機(jī)器的ID（5個(gè)bit是數(shù)據(jù)中心榨惠，5個(gè)bit的機(jī)器ID）奋早，12bit作為毫秒內(nèi)的流水號(hào)（意味著每個(gè)節(jié)點(diǎn)在每毫秒可以產(chǎn)生 4096 個(gè) ID），最后還有一個(gè)符號(hào)位赠橙，永遠(yuǎn)是0
4-2.png
application.yml添加工作機(jī)器配置
workerId: 0
datacenterId: 0
注入
@Value("${workerId}")
private Integer workerId;
@Value("${datacenterId}")
private Integer datacenterId;
@Bean
public IdWorker idWorker(){
return new IdWorker(workerId,datacenterId);
}
分享一個(gè)工具類
package com.changgou.utils;
import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
/**
* <p>名稱：IdWorker.java</p>
* <p>描述：分布式自增長ID</p>
* <pre>
* Twitter的 Snowflake JAVA實(shí)現(xiàn)方案
* </pre>
* 核心代碼為其IdWorker這個(gè)類實(shí)現(xiàn)耽装，其原理結(jié)構(gòu)如下，我分別用一個(gè)0表示一位期揪，用—分割開部分的作用：
* 1||0---0000000000 0000000000 0000000000 0000000000 0 --- 00000 ---00000 ---000000000000
* 在上面的字符串中掉奄，第一位為未使用（實(shí)際上也可作為long的符號(hào)位），接下來的41位為毫秒級(jí)時(shí)間横侦，
* 然后5位datacenter標(biāo)識(shí)位挥萌，5位機(jī)器ID（并不算標(biāo)識(shí)符，實(shí)際是為線程標(biāo)識(shí)）枉侧，
* 然后12位該毫秒內(nèi)的當(dāng)前毫秒內(nèi)的計(jì)數(shù)引瀑，加起來剛好64位，為一個(gè)Long型榨馁。
* 這樣的好處是憨栽，整體上按照時(shí)間自增排序，并且整個(gè)分布式系統(tǒng)內(nèi)不會(huì)產(chǎn)生ID碰撞（由datacenter和機(jī)器ID作區(qū)分），
* 并且效率較高屑柔，經(jīng)測(cè)試屡萤，snowflake每秒能夠產(chǎn)生26萬ID左右，完全滿足需要掸宛。
* <p>
* 64位ID (42(毫秒)+5(機(jī)器ID)+5(業(yè)務(wù)編碼)+12(重復(fù)累加))
*
* @author Polim
*/
public class IdWorker {
// 時(shí)間起始標(biāo)記點(diǎn)死陆，作為基準(zhǔn)，一般取系統(tǒng)的最近時(shí)間（一旦確定不能變動(dòng)）
private final static long twepoch = 1288834974657L;
// 機(jī)器標(biāo)識(shí)位數(shù)
private final static long workerIdBits = 5L;
// 數(shù)據(jù)中心標(biāo)識(shí)位數(shù)
private final static long datacenterIdBits = 5L;
// 機(jī)器ID最大值
private final static long maxWorkerId = -1L ^ (-1L << workerIdBits);
// 數(shù)據(jù)中心ID最大值
private final static long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
// 毫秒內(nèi)自增位
private final static long sequenceBits = 12L;
// 機(jī)器ID偏左移12位
private final static long workerIdShift = sequenceBits;
// 數(shù)據(jù)中心ID左移17位
private final static long datacenterIdShift = sequenceBits + workerIdBits;
// 時(shí)間毫秒左移22位
private final static long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
private final static long sequenceMask = -1L ^ (-1L << sequenceBits);
/* 上次生產(chǎn)id時(shí)間戳 */
private static long lastTimestamp = -1L;
// 0唧瘾，并發(fā)控制
private long sequence = 0L;
private final long workerId;
// 數(shù)據(jù)標(biāo)識(shí)id部分
private final long datacenterId;
public IdWorker(){
this.datacenterId = getDatacenterId(maxDatacenterId);
this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
}
/**
* @param workerId
* 工作機(jī)器ID
* @param datacenterId
* 序列號(hào)
*/
public IdWorker(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;
}
/**
* 獲取下一個(gè)ID
*
* @return
*/
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 (lastTimestamp == timestamp) {
// 當(dāng)前毫秒內(nèi)措译，則+1
sequence = (sequence + 1) & sequenceMask;
if (sequence == 0) {
// 當(dāng)前毫秒內(nèi)計(jì)數(shù)滿了，則等待下一秒
timestamp = tilNextMillis(lastTimestamp);
}
} else {
sequence = 0L;
}
lastTimestamp = timestamp;
// ID偏移組合生成最終的ID饰序，并返回ID
long nextId = ((timestamp - twepoch) << timestampLeftShift)
| (datacenterId << datacenterIdShift)
| (workerId << workerIdShift) | sequence;
return nextId;
}
private long tilNextMillis(final long lastTimestamp) {
long timestamp = this.timeGen();
while (timestamp <= lastTimestamp) {
timestamp = this.timeGen();
}
return timestamp;
}
private long timeGen() {
return System.currentTimeMillis();
}
/**
* <p>
* 獲取 maxWorkerId
* </p>
*/
protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {
StringBuffer mpid = new StringBuffer();
mpid.append(datacenterId);
String name = ManagementFactory.getRuntimeMXBean().getName();
if (!name.isEmpty()) {
/*
* GET jvmPid
*/
mpid.append(name.split("@")[0]);
}
/*
* MAC + PID 的 hashcode 獲取16個(gè)低位
*/
return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
}
/**
* <p>
* 數(shù)據(jù)標(biāo)識(shí)id部分
* </p>
*/
protected 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();
id = ((0x000000FF & (long) mac[mac.length - 1])
| (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
id = id % (maxDatacenterId + 1);
}
} catch (Exception e) {
System.out.println(" getDatacenterId: " + e.getMessage());
}
return id;
}
}
使用：
idWorker.nextId()
生成的id：
1161815962433880064
