redis分布式锁，无须设置有效期，自动检测hold锁的节点是否存活

1.有一个独立的keeplive守护线程保证节点存活，频率是n。
2.节点存活信息由固定前置+mac+进程id+进程启动时间，保证节点重启问题。
3. 锁的信息由固定前置+mac+进程id+进程启动时间。
4. 具体锁的逻辑参考lock方法。
package six.com.crawler.common;

import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;

import redis.clients.jedis.JedisCluster;

/**

• @author 作者
• @E-mail: 359852326@qq.com
• @date 创建时间：2017年5月27日 下午3:13:14

•   基于redis实现分布式锁,无需给锁key加上过期时间，程序会自动检测
  

  */
  public class RedisLock {

  private static long SYSTEM_START_TIME = System.currentTimeMillis();
  private static String mac;
  private static String pid;
  private static String nodeKeepliveInfoPre;

  static {
  String name = ManagementFactory.getRuntimeMXBean().getName();
  pid = name.split("@")[0];
  try {
  InetAddress ia = InetAddress.getLocalHost();
  byte[] macBytes = NetworkInterface.getByInetAddress(ia).getHardwareAddress();
  StringBuffer sb = new StringBuffer("");
  for (int i = 0; i < macBytes.length; i++) {
  int temp = macBytes[i] & 0xff;
  String str = Integer.toHexString(temp);
  if (str.length() == 1) {
  sb.append("0" + str);
  } else {
  sb.append(str);
  }
  }
  mac = sb.toString().toUpperCase();
  } catch (Exception e) {
  }
  nodeKeepliveInfoPre = mac + "_" + pid + "_" + SYSTEM_START_TIME + "_";
  }

  private Thread keepliveThread;
  private JedisCluster jedisCluster;
  private String nodeKeepliveInfoKeyPre;
  private String nodeKeepliveInfoKey;
  private long loopKeepliveInterval;
  private int keepliveInfoExpire;
  private long checkLockIntervalTime;

  public RedisLock(JedisCluster jedisCluster, String nodeKeepLiveInfoKeyPre, long loopKeepliveInterval,
  long checkLockIntervalTime) {
  this.jedisCluster = jedisCluster;
  this.nodeKeepliveInfoKeyPre = nodeKeepLiveInfoKeyPre;
  this.nodeKeepliveInfoKey = getNodeKeepliveInfoKey(mac, pid, String.valueOf(SYSTEM_START_TIME));
  this.loopKeepliveInterval = loopKeepliveInterval;
  this.keepliveInfoExpire = (int) (loopKeepliveInterval) / 1000 * 2;
  this.checkLockIntervalTime = checkLockIntervalTime;
  initKeepLive();
  }

  /**

  • 节点mac+进程id+进程启动时间保证节点重启问题
    */
    private void initKeepLive() {
    keepliveThread = new Thread(() -> {
    String nodeInfo = null;
    while (true) {
    nodeInfo = nodeKeepliveInfoPre + String.valueOf(System.currentTimeMillis());
    jedisCluster.set(nodeKeepliveInfoKey, nodeInfo);
    jedisCluster.expire(nodeKeepliveInfoKey, keepliveInfoExpire);
    try {
    Thread.sleep(loopKeepliveInterval);
    } catch (InterruptedException e) {
    }
    }

    }, "node-keeplive-thread");
    keepliveThread.setDaemon(true);
    keepliveThread.start();
    }

  public void lock(String lockKey) {
  while (true) {
  if (1 == jedisCluster.setnx(lockKey, getNodeLockInfo())) {
  break;
  }
  String nodeInfo = jedisCluster.get(lockKey);
  String nodeInfoKey = getNodeKeepliveInfoKey(nodeInfo);
  String lastKeepNodeInfo = jedisCluster.get(nodeInfoKey);
  do {
  try {
  Thread.sleep(checkLockIntervalTime);// 这个时间需要根据节点刷新时间取一个合适值
  } catch (InterruptedException e) {
  }
  String tempNodeInfo = jedisCluster.get(nodeInfoKey);
  if (isNotKeeplive(lastKeepNodeInfo, tempNodeInfo)) {
  // 证明节点挂了
  unlock(lockKey);
  break;
  } else {
  lastKeepNodeInfo = tempNodeInfo;
  }
  } while (true);
  }
  }

  /**

  • 判断目标节点是否还在线
  • @param lastKeepliveInfo
  • @param newKeepliveInfo
  • @return
    */
    private boolean isNotKeeplive(String lastKeepliveInfo, String newKeepliveInfo) {
    String[] lastMeta = lastKeepliveInfo.split("_");
    String[] newMeta = newKeepliveInfo.split("_");
    // mac pid 启动时间 系统时间
    if (lastMeta[0] != newMeta[0]) {
    // 当前Hold key的节点已被其他节点占据
    return true;
    } else {
    if (lastMeta[1] != newMeta[1]) {
    // pid发生变化表示节点已经重启
    return true;
    } else {
    if (lastMeta[2] != newMeta[2]) {
    // 启动时间发生变化表示节点已经重启
    return true;
    } else {
    if (lastMeta[3] != newMeta[3]) {
    // 系统时间发生变化表示节点正常存活
    return false;
    } else {
    return true;
    }
    }
    }
    }
    }

  public void unlock(String lockKey) {
  jedisCluster.del(lockKey);
  }

  private String getNodeLockInfo() {
  return mac + "_" + pid + "_" + SYSTEM_START_TIME + "_" + System.currentTimeMillis();
  }

  private String getNodeKeepliveInfoKey(String mac, String pid, String systemStartTime) {
  String nodeKeepLiveInfoKey = nodeKeepliveInfoKeyPre + mac + pid + systemStartTime;
  return nodeKeepLiveInfoKey;
  }

  private String getNodeKeepliveInfoKey(String nodeLockInfo) {
  String[] meta = nodeLockInfo.split("_");
  return getNodeKeepliveInfoKey(meta[0], meta[1], meta[2]);
  }

}