分布式环境下唯一id确实算个问题,今天分享的算法自己项目已经跑了两年,效率高也没出现重复情况;
直接上干货:
核心两个类:
package com.longbei.appservice.common; import java.sql.Timestamp; import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.ThreadFactory; import java.util.concurrent.TimeUnit; import java.util.concurrent.atomic.AtomicLong; /** * 高并发场景下System.currentTimeMillis()的性能问题的优化 * <p><p> * System.currentTimeMillis()的调用比new一个普通对象要耗时的多(具体耗时高出多少我还没测试过,有人说是100倍左右)<p> * System.currentTimeMillis()之所以慢是因为去跟系统打了一次交道<p> * 后台定时更新时钟,JVM退出时,线程自动回收<p> * 10亿:43410,206,210.72815533980582%<p> * 1亿:4699,29,162.0344827586207%<p> * 1000万:480,12,40.0%<p> * 100万:50,10,5.0%<p> * @author lry */ public class SystemClock { private final long period; private final AtomicLong now; private SystemClock(long period) { this.period = period; this.now = new AtomicLong(System.currentTimeMillis()); scheduleClockUpdating(); } private static class InstanceHolder { public static final SystemClock INSTANCE = new SystemClock(1); } private static SystemClock instance() { return InstanceHolder.INSTANCE; } private void scheduleClockUpdating() { ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor(new ThreadFactory() { public Thread newThread(Runnable runnable) { Thread thread = new Thread(runnable, "System Clock"); thread.setDaemon(true); return thread; } }); scheduler.scheduleAtFixedRate(new Runnable() { public void run() { now.set(System.currentTimeMillis()); } }, period, period, TimeUnit.MILLISECONDS); } private long currentTimeMillis() { return now.get(); } public static long now() { return instance().currentTimeMillis(); } public static String nowDate() { return new Timestamp(instance().currentTimeMillis()).toString(); } }
package com.longbei.appservice.common; /** * 分布式高效有序ID生产黑科技(sequence) * * @author lry */ public class Sequence { private final long twepoch = 1288834974657L; private final long workerIdBits = 5L; private final long datacenterIdBits = 5L; private final long maxWorkerId = -1L ^ (-1L << workerIdBits); private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits); private final long sequenceBits = 12L; private final long workerIdShift = sequenceBits; private final long datacenterIdShift = sequenceBits + workerIdBits; private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits; private final long sequenceMask = -1L ^ (-1L << sequenceBits); private long workerId; private long datacenterId; private long sequence = 0L; private long lastTimestamp = -1L; /** * @param workerId 工作机器ID * @param datacenterId 序列号 */ public Sequence(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; } /** * 获取下一个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) { sequence = (sequence + 1) & sequenceMask; if (sequence == 0) { timestamp = tilNextMillis(lastTimestamp); } } else { sequence = 0L; } lastTimestamp = timestamp; return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence; } protected long tilNextMillis(long lastTimestamp) { long timestamp = timeGen(); while (timestamp <= lastTimestamp) { timestamp = timeGen(); } return timestamp; } protected long timeGen() { return SystemClock.now(); } }
private static SFSequence sequ = new SFSequence(machineId%32,0);
** * 内存方式分配全局唯一ID * * @author shuzc 总共四种方式,getNextId,getUniqueIdAsString,getNextId和数据库自增id. * 1.用户id用getNextId;如果分表按最后2 ~ 3位分即可 * 2.订单id用getUniqueIdAsString,最好在这个串的前面添加某个前缀,如果想在中间添加,修改下代码;如果分表按最后2 ~ * 3位分即可 3.商品id用getNextId,如果分表按最后2 ~ 3位分即可 4.进步id用getNextId,这个应该没有分表需求 * 5.点赞记录的id,或者一些流水性质的,比如用户操作记录等,这些记录应该只有查询的场景,没有更新等场景;用数据库自增id, * 或者getUniqueIdAsLong,这种分表也不会利用主键的 * @return */ @Service @SuppressWarnings("hiding") public class IdGenerateService { private static int MAX_TRY_TIMES = 20; private static long machineId = calculateMachineId(); private static final SimpleDateFormat DATE_TIME_FORMAT = new SimpleDateFormat("yyyyMMddHHmmss"); private static final SimpleDateFormat SHORT_DATE_TIME_FORMAT = new SimpleDateFormat("yyMMddHHmmss"); private static final String MACHINE_ID_FORMAT = "%1d"; private static final AtomicLong seq = new AtomicLong(0); private static long calculateMachineId() { try { for (NetworkInterface iface : Collections.list(NetworkInterface.getNetworkInterfaces())) { for (InetAddress raddr : Collections.list(iface.getInetAddresses())) { if (raddr.isSiteLocalAddress() && !raddr.isLoopbackAddress() && !(raddr instanceof Inet6Address)) { return getLocalMac(raddr); } } } } catch (SocketException e) { throw new IllegalStateException("fail to get host ip"); } throw new IllegalStateException("fail to get host ip"); } private static long getLocalMac(InetAddress ia) throws SocketException { byte[] mac = NetworkInterface.getByInetAddress(ia).getHardwareAddress(); int temp = 0; StringBuffer sb = new StringBuffer(""); for (int i = 0; i < mac.length; i++) { if (i != 0) { sb.append("-"); } temp ^= (mac[i] & 0xff); } // 与时间异或,更有利于排除重复的可能 return temp ^ (System.currentTimeMillis() % 100); } public Long getUniqueIdAsLong() { return sequ.nextId(); } private static SFSequence sequ = new SFSequence(machineId%32,0);for (InetAddress raddr : Collections. list(iface.getInetAddresses())) { if (raddr.isSiteLocalAddress() && !raddr.isLoopbackAddress() && !(raddr instanceof Inet6Address)) { return getLocalMac(raddr) ; } } } } catch (SocketException e) { throw new IllegalStateException( "fail to get host ip") ; } throw new IllegalStateException( "fail to get host ip") ;}
}
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