IdServiceImpl.java

package com.robert.vesta.service.impl;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

import com.robert.vesta.service.bean.Id;
import com.robert.vesta.service.impl.bean.IdType;
import com.robert.vesta.service.intf.IdService;

public class IdServiceImpl extends AbstractIdServiceImpl implements IdService {
	private long sequence = 0;

	private long lastTimestamp = -1;

	private Lock lock = new ReentrantLock();

	public IdServiceImpl() {
		super();
	}

	public IdServiceImpl(String type) {
		super(type);
	}

	public IdServiceImpl(IdType type) {
		super(type);
	}

	protected void populateId(Id id) {
		lock.lock();
		try {
			long timestamp = this.genTime();
			validateTimestamp(lastTimestamp, timestamp);

			if (timestamp == lastTimestamp) {
				sequence++;
				sequence &= idMeta.getSeqBitsMask();
				if (sequence == 0) {
					timestamp = this.tillNextTimeUnit(lastTimestamp);
				}
			} else {
				lastTimestamp = timestamp;
				sequence = 0;
			}

			id.setSeq(sequence);
			id.setTime(timestamp);

		} finally {
			lock.unlock();
		}
	}

	private void validateTimestamp(long lastTimestamp, long timestamp) {
		if (timestamp < lastTimestamp) {
			if (log.isErrorEnabled())
				log.error(String
						.format("Clock moved backwards.  Refusing to generate id for %d %s.",
								lastTimestamp - timestamp,
								idType == IdType.MAX_PEAK ? "second"
										: "milisecond"));

			throw new IllegalStateException(
					String.format(
							"Clock moved backwards.  Refusing to generate id for %d %s.",
							lastTimestamp - timestamp,
							idType == IdType.MAX_PEAK ? "second" : "milisecond"));
		}
	}

	protected long tillNextTimeUnit(final long lastTimestamp) {
		if (log.isInfoEnabled())
			log.info(String
					.format("Ids are used out during %d in machine %d. Waiting till next %s.",
							lastTimestamp, machineId,
							idType == IdType.MAX_PEAK ? "second" : "milisecond"));

		long timestamp = this.genTime();
		while (timestamp <= lastTimestamp) {
			timestamp = this.genTime();
		}

		if (log.isInfoEnabled())
			log.info(String.format("Next %s %d is up.",
					idType == IdType.MAX_PEAK ? "second" : "milisecond",
					timestamp));

		return timestamp;
	}
}