IncrSequenceTimeHandler.java

package io.mycat.server.sequence;

import io.mycat.server.config.node.SequenceConfig;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Map;

public class IncrSequenceTimeHandler extends SequenceHandler {
	protected static final Logger LOGGER = LoggerFactory
			.getLogger(IncrSequenceTimeHandler.class);

	private static final IncrSequenceTimeHandler instance = new IncrSequenceTimeHandler();
	private static IdWorker workey = new IdWorker(0,0);

	public static SequenceHandler getInstance() {
		return IncrSequenceTimeHandler.instance;
	}

	static{
		SequenceConfig sequenceConfig = SequenceHandler.getConfig();
		Map<String, Object> props = sequenceConfig.getProps();
		if(!props.isEmpty()){
			long workerId =  Integer.valueOf((String)props.get("WORKID")) ;
			long datacenterId = Integer.valueOf((String)props.get("DATAACENTERID")) ;
			IncrSequenceTimeHandler.instance.setWorkey(new IdWorker(workerId,datacenterId) );
		}
	}

	private IncrSequenceTimeHandler() {

	}

	@Override
	public long nextId(String prefixName) {
		return workey.nextId();
	}


	/**
	* 64位ID (42(毫秒)+5(机器ID)+5(业务编码)+12(重复累加))
	* @author sw
	*/
	static class IdWorker {
		private final static long twepoch = 1288834974657L;
		// 机器标识位数
		private final static long workerIdBits = 5L;
		// 数据中心标识位数
		private final static long datacenterIdBits = 5L;
		// 机器ID最大值 31
		private final static long maxWorkerId = -1L ^ (-1L << workerIdBits);
		// 数据中心ID最大值 31
		private final static long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
		// 毫秒内自增位
		private final static long sequenceBits = 12L;
		// 机器ID偏左移12位
		private final static long workerIdShift = sequenceBits;
		// 数据中心ID左移17位
		private final static long datacenterIdShift = sequenceBits + workerIdBits;
		// 时间毫秒左移22位
		private final static long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;

		private final static long sequenceMask = -1L ^ (-1L << sequenceBits);

		private static long lastTimestamp = -1L;

		private long sequence = 0L;
		private final long workerId;
		private final long datacenterId;

		public IdWorker(long workerId, long datacenterId) {
			if (workerId > maxWorkerId || workerId < 0) {
				throw new IllegalArgumentException("worker Id can't be greater than %d or less than 0");
			}
			if (datacenterId > maxDatacenterId || datacenterId < 0) {
				throw new IllegalArgumentException("datacenter Id can't be greater than %d or less than 0");
			}
			this.workerId = workerId;
			this.datacenterId = datacenterId;
		}

		public synchronized long nextId() {
			long timestamp = timeGen();
			if (timestamp < lastTimestamp) {
			try {
				throw new Exception("Clock moved backwards.  Refusing to generate id for "+ (lastTimestamp - timestamp) + " milliseconds");
			} catch (Exception e) {
				e.printStackTrace();
			}
			}

			if (lastTimestamp == timestamp) {
				// 当前毫秒内，则+1
				sequence = (sequence + 1) & sequenceMask;
				if (sequence == 0) {
					// 当前毫秒内计数满了，则等待下一秒
					timestamp = tilNextMillis(lastTimestamp);
				}
			} else {
				sequence = 0;
			}
			lastTimestamp = timestamp;
			// ID偏移组合生成最终的ID，并返回ID
			return ((timestamp - twepoch) << timestampLeftShift)
					| (datacenterId << datacenterIdShift)
					| (workerId << workerIdShift) | sequence;
		}

		private long tilNextMillis(final long lastTimestamp) {
			long timestamp = this.timeGen();
			while (timestamp <= lastTimestamp) {
				timestamp = this.timeGen();
			}
			return timestamp;
		}

		private long timeGen() {
			return System.currentTimeMillis();
		}



	}

	public void setWorkey(IdWorker workey) {
		IncrSequenceTimeHandler.workey = workey;
	}




}