先说一次遇到的问题
关于redis分布式锁的问题，
先来一个遇到问题的代码
/** 错误示范 */ public boolean lock(final String lockKey) { for(String lock : locks) { if (lock.equals(lockKey)) { return true; } } Long i = jedisClient.execute(new JedisAction<Long>() { @Override public Long doAction(Jedis jedis) { //这个地方上锁 Long i = jedis.setnx(lockKey, "1"); if( i == null ) { return 0L; } if(i == 1) { //这个地方设置有效时间 jedis.expire(lockKey, LOCKKEY_EXPIRE_TIME); locks.add(lockKey); if(LOGGER.isInfoEnabled()) { LOGGER.info("添加锁 [{}]",lockKey); } } return i; } }); return i == 1; }以上代码的问题在于 把上锁和设置有效时间分开了，所以导致停服的时候正好上了锁，但是没有设置有效时间，所以一直有问题
那么redis应该如何正确有效的上锁呢
目前的setnx完全可以在一个方法里面实现有效时间和key
import org.slf4j.Logger; import org.slf4j.LoggerFactory; import redis.clients.jedis.JedisPool; /** * 基于redis setnx的 分布式锁 实, 前提是所有的锁都要有锁定时间. * 获取锁的时候,需要指定value,在unlock的时候,会根据value判断是否remove */ public class RedisLockUtil { private static final String LOCK_PREFIX = "LOCK"; private static final Integer DEFAULT_LOCK_TIME = 10;// 默认锁定时间秒 private static final Long DEFAULT_SLEEP_TIME = 100L;// 默认sleep时间,100毫秒 private static Logger logger = LoggerFactory.getLogger(RedisLockUtil.class); /** * 获取缓存的value,随机值,使不同的锁value不同 (多服务器可以使用redis时间+客户端标识等) * * @return */ public static String getLockValue() { int random = (int) ((Math.random() * 9 + 1) * 100000); long now = System.currentTimeMillis(); return String.valueOf(now) + String.valueOf(random); } /** * 获取锁,如果失败,自动重试 * * @param key * @param value * @return */ public static boolean lock(JedisPool jedisPool, String key, String value) { return lock(jedisPool, key, value, DEFAULT_LOCK_TIME); } /** * 获取锁,如果失败,自动重试 * * @param key * @param value * @param lockTime 获取成功后的锁定时间 * @return */ public static boolean lock(JedisPool jedisPool, String key, String value, int lockTime) { return lock(jedisPool, key, value, lockTime, true); } private static boolean lock(JedisPool jedisPool, String key, String value, int lockTime, boolean reTry) { return lock(jedisPool, key, value, lockTime, reTry, 0, false, 0); } /** * 获取锁,如果失败,直接返回false * * @param key * @param value * @return */ public static boolean tryLock(JedisPool jedisPool, String key, String value) { return tryLock(jedisPool, key, value, DEFAULT_LOCK_TIME); } /** * 获取锁,如果失败,直接返回false * * @param key * @param value * @param lockTime 获取成功后的锁定时间 * @return */ public static boolean tryLock(JedisPool jedisPool, String key, String value, int lockTime) { return lock(jedisPool, key, value, lockTime, false); } /** * 尝试获取锁,如果获取失败,重试,直到成功或超出指定时间 * * @param key * @param value * @param lockTime 获取成功后的锁定时间 * @param timeOut 获取锁等待超时时间 * @return */ public static boolean tryLock(JedisPool jedisPool, String key, String value, int lockTime, long timeOutMillis) { return lock(jedisPool, key, value, lockTime, true, 0, true, timeOutMillis); } /** * 释放锁,key对应的value于参数value一致,才删除key * * @param key * @param value */ public static boolean unlock(JedisPool jedisPool, String key, String value) { String fullKey = getFullKey(key); boolean success = JedisUtil.unlock(jedisPool, fullKey, value); if (success) { logger.info("unlock success ; key:" + key + ",value:" + value); } else { logger.info("unlock failed ; key:" + key + ",value:" + value); } return success; } /** * 获取锁 * * @param key * @param value * @param lockTime 锁定时间 * @param reTry 失败是否重试 * @param curTryTime 当前尝试次数 * @param needTimeOut 是否需要判断超时时间 * @param timeOutMillis 尝试超时时间(毫秒) * @return */ private static boolean lock(JedisPool jedisPool, String key, String value, int lockTime, boolean reTry, int curTryTime, boolean needTimeOut, long timeOutMillis) { logger.info(Thread.currentThread().getName() + ",lock come in ; key:" + key + ",value:" + value + ",lockTime:" + lockTime + ",reTry:" + reTry + ",curTryTime:" + curTryTime + ",needTimeOut:" + needTimeOut + ",timeOutMillis:" + timeOutMillis); curTryTime++; String fullKey = getFullKey(key); // setnx 并设置超时时间 boolean success = JedisUtil.setnx(jedisPool, fullKey, value, (long) lockTime * 1000); // 获取成功,直接返回 if (success) { logger.info("lock success ; key:" + key + ",value:" + value + ",lockTime:" + lockTime + ",reTry:" + reTry + ",curTryTime:" + curTryTime + ",needTimeOut:" + needTimeOut + ",timeOutMillis:" + timeOutMillis); return true; } // 获取失败,不需要重试,直接返回 if (!reTry) { logger.info("lock failed ; key:" + key + ",value:" + value + ",lockTime:" + lockTime + ",reTry:" + reTry + ",curTryTime:" + curTryTime + ",needTimeOut:" + needTimeOut + ",timeOutMillis:" + timeOutMillis); return false; } // 获取失败, 且已超时,返回 if (needTimeOut && timeOutMillis <= 0) { logger.info("lock failed ; key:" + key + ",value:" + value + ",lockTime:" + lockTime + ",reTry:" + reTry + ",curTryTime:" + curTryTime + ",needTimeOut:" + needTimeOut + ",timeOutMillis:" + timeOutMillis); return false; } // 获取sleep时间 long sleepMillis = getSleepMillis(needTimeOut, timeOutMillis); // sleep后重新获取锁 sleep(sleepMillis); // 大于100次,打印warning日志 if (curTryTime > 100) { logger.warn("lock warning ; key:" + key + ",value:" + value + ",lockTime:" + lockTime + ",reTry:" + reTry + ",curTryTime:" + curTryTime + ",needTimeOut:" + needTimeOut + ",timeOutMillis:" + timeOutMillis); } return lock(jedisPool, key, value, lockTime, reTry, curTryTime, needTimeOut, timeOutMillis); } private static long getSleepMillis(boolean needTimeOut, long timeOutMillis) { long sleepMillis = DEFAULT_SLEEP_TIME; if (needTimeOut) { timeOutMillis = timeOutMillis - DEFAULT_SLEEP_TIME; if (timeOutMillis < DEFAULT_SLEEP_TIME) { sleepMillis = timeOutMillis; } } return sleepMillis; } private static void sleep(long sleepMillis) { try { Thread.sleep(sleepMillis); } catch (InterruptedException e) { e.printStackTrace(); } } public static String getFullKey(String key) { return LOCK_PREFIX + ":" + key; } }
