redis 分布式锁基本实现

manongxiaomei 2020-06-12

import cn.xa87.common.lock.AbstractDistributedLock;import lombok.extern.slf4j.Slf4j;import org.springframework.data.redis.core.RedisCallback;import org.springframework.data.redis.core.RedisTemplate;import org.springframework.util.StringUtils;import redis.clients.jedis.Jedis;import redis.clients.jedis.JedisCluster;import redis.clients.jedis.JedisCommands;import java.util.ArrayList;import java.util.List;import java.util.UUID;@Slf4jpublic class RedisDistributedLock extends AbstractDistributedLock {    private RedisTemplate<String, String> redisTemplate;    private ThreadLocal<String> lockFlag = new ThreadLocal<>();    private static final String UNLOCK_LUA;    /*     * 通过lua脚本释放锁,来达到释放锁的原子操作     */    static {        UNLOCK_LUA = "if redis.call(\"get\",KEYS[1]) == ARGV[1] " +                "then " +                "    return redis.call(\"del\",KEYS[1]) " +                "else " +                "    return 0 " +                "end ";    }    public RedisDistributedLock(RedisTemplate<String, String> redisTemplate) {        super();        this.redisTemplate = redisTemplate;    }    /**     * 获取锁     *     * @param key         key     * @param expire      获取锁超时时间     * @param retryTimes  重试次数     * @param sleepMillis 获取锁失败的重试间隔     * @return 成功/失败     */    @Override    public boolean lock(String key, long expire, int retryTimes, long sleepMillis) {        boolean result = setRedis(key, expire);        // 如果获取锁失败,按照传入的重试次数进行重试        while ((!result) && retryTimes-- > 0) {            try {                log.debug("get redisDistributeLock failed, retrying..." + retryTimes);                Thread.sleep(sleepMillis);            } catch (InterruptedException e) {                return false;            }            result = setRedis(key, expire);        }        return result;    }    private boolean setRedis(final String key, final long expire) {        try {            String result = redisTemplate.execute((RedisCallback<String>) connection -> {                JedisCommands commands = (JedisCommands) connection.getNativeConnection();                String uuid = UUID.randomUUID().toString();                lockFlag.set(uuid);                return commands.set(key, uuid, "NX", "PX", expire);            });            return !StringUtils.isEmpty(result);        } catch (Exception e) {            log.error("set redisDistributeLock occured an exception", e);        }        return false;    }    @Override    public boolean releaseLock(String key) {        // 释放锁的时候,有可能因为持锁之后方法执行时间大于锁的有效期,此时有可能已经被另外一个线程持有锁,所以不能直接删除        try {            final List<String> keys = new ArrayList<>();            keys.add(key);            final List<String> args = new ArrayList<>();            args.add(lockFlag.get());            // 使用lua脚本删除redis中匹配value的key,可以避免由于方法执行时间过长而redis锁自动过期失效的时候误删其他线程的锁            // spring自带的执行脚本方法中,集群模式直接抛出不支持执行脚本的异常,所以只能拿到原redis的connection来执行脚本            Long result = redisTemplate.execute((RedisCallback<Long>) connection -> {                Object nativeConnection = connection.getNativeConnection();                // 集群模式和单机模式虽然执行脚本的方法一样,但是没有共同的接口,所以只能分开执行                // 集群模式                if (nativeConnection instanceof JedisCluster) {                    return (Long) ((JedisCluster) nativeConnection).eval(UNLOCK_LUA, keys, args);                }                // 单机模式                else if (nativeConnection instanceof Jedis) {                    return (Long) ((Jedis) nativeConnection).eval(UNLOCK_LUA, keys, args);                }                return 0L;            });            return result != null && result > 0;        } catch (Exception e) {            log.error("release redisDistributeLock occured an exception", e);        } finally {            lockFlag.remove();        }        return false;    }}
/** * 分布式锁抽象类 * */public abstract class AbstractDistributedLock implements DistributedLock{    /**     * 获取锁     *     * @param key         key     * @return 成功/失败     */    @Override    public boolean lock(String key) {        return lock(key, TIMEOUT_MILLIS, RETRY_TIMES, SLEEP_MILLIS);    }    /**     * 获取锁     *     * @param key         key     * @param retryTimes  重试次数     * @return 成功/失败     */    @Override    public boolean lock(String key, int retryTimes) {        return lock(key, TIMEOUT_MILLIS, retryTimes, SLEEP_MILLIS);    }    /**     * 获取锁     *     * @param key         key     * @param retryTimes  重试次数     * @param sleepMillis 获取锁失败的重试间隔     * @return 成功/失败     */    @Override    public boolean lock(String key, int retryTimes, long sleepMillis) {        return lock(key, TIMEOUT_MILLIS, retryTimes, sleepMillis);    }    /**     * 获取锁     *     * @param key         key     * @param expire      获取锁超时时间     * @return 成功/失败     */    @Override    public boolean lock(String key, long expire) {        return lock(key, expire, RETRY_TIMES, SLEEP_MILLIS);    }    /**     * 获取锁     *     * @param key         key     * @param expire      获取锁超时时间     * @param retryTimes  重试次数     * @return 成功/失败     */    @Override    public boolean lock(String key, long expire, int retryTimes) {        return lock(key, expire, retryTimes, SLEEP_MILLIS);    }}
/** * 分布式锁顶级接口 * */public interface DistributedLock {    /**     * 默认超时时间     */    long TIMEOUT_MILLIS = 3000;    int RETRY_TIMES = 2;    long SLEEP_MILLIS = 100;    /**     * 获取锁     *     * @param key key     * @return 成功/失败     */    boolean lock(String key);    /**     * 获取锁     *     * @param key        key     * @param retryTimes 重试次数     * @return 成功/失败     */    boolean lock(String key, int retryTimes);    /**     * 获取锁     *     * @param key         key     * @param retryTimes  重试次数     * @param sleepMillis 获取锁失败的重试间隔     * @return 成功/失败     */    boolean lock(String key, int retryTimes, long sleepMillis);    /**     * 获取锁     *     * @param key    key     * @param expire 获取锁超时时间     * @return 成功/失败     */    boolean lock(String key, long expire);    /**     * 获取锁     *     * @param key        key     * @param expire     获取锁超时时间     * @param retryTimes 重试次数     * @return 成功/失败     */    boolean lock(String key, long expire, int retryTimes);    /**     * 获取锁     *     * @param key         key     * @param expire      获取锁超时时间     * @param retryTimes  重试次数     * @param sleepMillis 获取锁失败的重试间隔     * @return 成功/失败     */    boolean lock(String key, long expire, int retryTimes, long sleepMillis);    /**     * 释放锁     *     * @param key key值     * @return 释放结果     */    boolean releaseLock(String key);}

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