Redis分布式代理锁的两种实现

一、引言

        分布式环境中的业务开发，Synchronized、ReentrantLock等本地锁已经不能再防止并发冲突，分布式锁应运而生。Redis分布式锁是目前最火热的锁工具之一，但是项目中对于并发的控制加锁解锁非常频繁，冗余代码较多，锁管理分散。

        本文基于Redisson通过两种方式实现代理分布式锁：

                1、ThreadLocal线程缓存 + AOP切面

                2、AOP切面 + 入参固定

二、未使用代理组件

未使用代理组建的情况下，一旦需要加锁都会进行以下编码，除了业务处理其他代码在业务功能中随处可见，冗余了许多非必要代码。

String lockKey = RedisConsts.ORDER_ID_LOCK + orderId;
RLock lock = redissonClient.getLock(lockKey);
try {
    if (lock.tryLock(RedisConsts.WAIT, RedisConsts.EXECUTE, RedisConsts.TIME_UNIT)) {
        //订单处理
    } else {
        log.error("加锁失败:{}",lockKey);
    }
} catch (InterruptedException e) {
    log.error("获取锁异常:{}", e);
    throw new BusinessException(ErrorCodeEnum.FAILED_TO_ACQUIRE_LOCK);
} finally {
    if (lock.isHeldByCurrentThread()) {
        lock.unlock();
    }
}

三、使用代理组件

1、注解

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RedisLock {
   String key();

    long waitOut() default 60;

    long executeOut() default 60;

    TimeUnit timeUnit() default TimeUnit.SECONDS;

    //是否自动清除LockUtil
    boolean atuoRemove() default false;
    String suffixKeyTypeEnum() default RedisLockCommonUtil.THREAD_LOCAL;
    String objectName() default "";
    String[] paramName() default {};
}

2、代理锁工具类

public class LockUtil {

    static ThreadLocal LOCK_KEY = new ThreadLocal();

    public static void set(String key) {
        LOCK_KEY.set(key);
    }

    public static String get() {
        return LOCK_KEY.get();
    }

    public static void remove() {
        LOCK_KEY.remove();
    }

}

3、切面

个人更喜欢使用ThreadLocal。

使用固定入参需要解析参数，会增加一些性能消耗，虽然对于越来越快的计算性能，这点消耗可以忽略。

① 使用ThreadLocal（适用于责任链、工厂模式等长链路模式）

@Slf4j
@Aspect
@Component
public class RedisLockAspect {

    @Resource
    private RedissonClient redissonClient;
    @Pointcut("@annotation(***.aspect.redislock.annotation.RedisLock)")
    public void lockPointCut() {
    }

    @Around("lockPointCut() && @annotation(redisLock)")
    public Object around(ProceedingJoinPoint joinPoint, RedisLock redisLock) {
        String lockKey = redisLock.key();
        if (Objects.nonNull(LockUtil.get())) {
            //获取线程缓存中的锁后缀
            lockKey += LockUtil.get();
        }
        log.info("开始代理加锁:{}",lockKey);
        RLock lock = redissonClient.getLock(lockKey);
        try {
            if (lock.tryLock(redisLock.waitOut(), redisLock.executeOut(), redisLock.timeUnit())) {
                log.info("代理加锁成功:{}",lockKey);
                return joinPoint.proceed();
            } else {
                log.warn("代理加锁失败:{}",lockKey);
            }
        } catch (InterruptedException e) {
            log.error("获取代理锁异常:{}", e);
            throw new BusinessException(ErrorCodeEnum.FAILED_TO_ACQUIRE_LOCK);
        } finally {
            if (lock.isHeldByCurrentThread()) {
                lock.unlock();
                log.info("代理解锁:{}",lockKey);
            }
            //如果方法注解中开启自动清除，就去除
            if (redisLock.atuoRemove()) {
                LockUtil.remove();
                log.info("自动清除LockUtil:{}",lockKey);
            }
        }
        return null;
    }


}

② 使用固定入参（适用于分散型方法）

@Slf4j
@Aspect
@Component
public class RedisLockAspect {

    @Resource
    private RedissonClient redissonClient;
    @Pointcut("@annotation(***.aspect.redislock.annotation.RedisLock)")
    public void lockPointCut() {
    }

    //定义固定入参名，业务使用时需要定义相同的参数名并传入下游方法
    private final static String REDIS_KEY = "redisKey";
    @Around("lockPointCut() && @annotation(redisLock)")
    public void around(ProceedingJoinPoint joinPoint, RedisLock redisLock) {
        String objectName = redisLock.objectName();
        if (StringUtil.isBlank(objectName)) {
            throw new BusinessException("objectName为空");
        }
        String[] paramName = redisLock.paramName();
        Object[] args = joinPoint.getArgs();
        String[] objectNames = ((CodeSignature) joinPoint.getSignature()).getParameterNames();
        Map objectHashMap = new HashMap<>();
        for (int i = 0; i < objectNames.length; i++) {
            objectHashMap.put(objectNames[i], args[i]);
        }
        if (!objectHashMap.containsKey(objectName)) {
            throw new BusinessException("入参不包含该对象" + objectName);
        }
        Object o = objectHashMap.get(objectName);
        if (paramName == null || paramName.length == 0) {
            return redisLock.key() + o;
        }
        String lockKey = redisLock.key();
        for (int i = 0; i < paramName.length; i++) {
            lockKey += RedisLockCommonUtil.getFieldValueByName(paramName[i], o);
        }
        log.info("开始代理加锁:{}",lockKey);
        RLock lock = redissonClient.getLock(lockKey);
        try {
            if (lock.tryLock(redisLock.waitOut(), redisLock.executeOut(), redisLock.timeUnit())) {
                log.info("代理加锁成功:{}",lockKey);
                joinPoint.proceed();
            }
        } catch (InterruptedException e) {
            log.error("获取代理锁异常:{}", e);
            throw new BusinessException(ErrorCodeEnum.FAILED_TO_ACQUIRE_LOCK);
        } finally {
            if (lock.isHeldByCurrentThread()) {
                lock.unlock();
                log.info("代理解锁:{}",lockKey);
            }
        }
    }
}

三、DEMO测试

1、模拟并发，两个可以同时进行，第三个线程有锁争抢

Thread lock1 = new Thread(
        new Runnable() {
            @Override
            public void run() {
                snChainDTO1.setSn("666sn");
                LockUtil.set(snChainDTO1.getSn());
                lockProcess.process(snChainDTO1);
            }
        }
);
lock1.start();
log.info("lock1 start");
MacSnChainDTO snChainDTO2 = new MacSnChainDTO();
Thread lock2 = new Thread(
        new Runnable() {
            @Override
            public void run() {
                snChainDTO2.setSn("888sn");
                LockUtil.set(snChainDTO2.getSn());
                lockProcess.process(snChainDTO2);
            }
        }
);
lock2.start();
log.info("lock2 start");
MacSnChainDTO snChainDTO3 = new MacSnChainDTO();
Thread lock3 = new Thread(
        new Runnable() {
            @Override
            public void run() {
                snChainDTO3.setSn("666sn");
                LockUtil.set(snChainDTO3.getSn());
                lockProcess.process(snChainDTO3);
            }
        }
);
lock3.start();
log.info("lock3 start");

 2、测试业务方法

@RedisLock(key = RedisPrefixConstant.DAMAGE_SN_LOCK_KEY, atuoRemove = true)
public void process(MacSnChainDTO macSnChainDTO) {
    for (int i = 0; i < 6; i++) {
        log.info("测试加锁:{}", LockUtil.get() + i);
    }
}

3、测试结果

2022-04-11 16:02:58.027 bit [http-nio-8189-exec-1] INFO  c.enmonster.bit.controller.testlock.LockEnterImpl.lockTogether:58 - lock1 start
2022-04-11 16:02:58.028 bit [http-nio-8189-exec-1] INFO  c.enmonster.bit.controller.testlock.LockEnterImpl.lockTogether:74 - lock2 start
2022-04-11 16:02:58.029 bit [Thread-98] INFO  c.e.bit.config.redislock.aspect.RedisLockAspect.around:36 - 开始代理加锁:BIT:LOCK:DAMAGE:SN:888sn
2022-04-11 16:02:58.029 bit [Thread-97] INFO  c.e.bit.config.redislock.aspect.RedisLockAspect.around:36 - 开始代理加锁:BIT:LOCK:DAMAGE:SN:666sn
2022-04-11 16:02:58.030 bit [http-nio-8189-exec-1] INFO  c.enmonster.bit.controller.testlock.LockEnterImpl.lockTogether:90 - lock3 start
2022-04-11 16:02:58.031 bit [Thread-99] INFO  c.e.bit.config.redislock.aspect.RedisLockAspect.around:36 - 开始代理加锁:BIT:LOCK:DAMAGE:SN:666sn
2022-04-11 16:02:58.033 bit [http-nio-8189-exec-1] INFO  c.enmonster.bit.controller.testlock.LockEnterImpl.logAround:52 - method: lockTogether, result: {"success":true}, span: 23
2022-04-11 16:02:58.063 bit [Thread-97] INFO  c.e.bit.config.redislock.aspect.RedisLockAspect.around:40 - 代理加锁成功:BIT:LOCK:DAMAGE:SN:666sn
2022-04-11 16:02:58.066 bit [Thread-98] INFO  c.e.bit.config.redislock.aspect.RedisLockAspect.around:40 - 代理加锁成功:BIT:LOCK:DAMAGE:SN:888sn
2022-04-11 16:02:58.067 bit [Thread-98] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:888sn0
2022-04-11 16:02:58.067 bit [Thread-97] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:666sn0
2022-04-11 16:02:58.068 bit [Thread-98] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:888sn1
2022-04-11 16:02:58.068 bit [Thread-97] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:666sn1
2022-04-11 16:02:58.068 bit [Thread-98] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:888sn2
2022-04-11 16:02:58.068 bit [Thread-97] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:666sn2
2022-04-11 16:02:58.068 bit [Thread-98] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:888sn3
2022-04-11 16:02:58.068 bit [Thread-97] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:666sn3
2022-04-11 16:02:58.068 bit [Thread-97] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:666sn4
2022-04-11 16:02:58.068 bit [Thread-98] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:888sn4
2022-04-11 16:02:58.068 bit [Thread-97] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:666sn5
2022-04-11 16:02:58.068 bit [Thread-98] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:888sn5
2022-04-11 16:02:58.084 bit [Thread-97] INFO  c.e.bit.config.redislock.aspect.RedisLockAspect.around:48 - 代理解锁:BIT:LOCK:DAMAGE:SN:666sn
2022-04-11 16:02:58.084 bit [Thread-97] INFO  c.enmonster.bit.controller.testlock.LockEnterImpl.run:51 - lock1-LockUtil:666sn
2022-04-11 16:02:58.084 bit [Thread-97] INFO  c.enmonster.bit.controller.testlock.LockEnterImpl.run:53 - 自动清除LockUti:BIT:LOCK:DAMAGE:SN:666sn
2022-04-11 16:02:58.090 bit [Thread-98] INFO  c.e.bit.config.redislock.aspect.RedisLockAspect.around:48 - 代理解锁:BIT:LOCK:DAMAGE:SN:888sn
2022-04-11 16:02:58.091 bit [Thread-98] INFO  c.enmonster.bit.controller.testlock.LockEnterImpl.run:67 - lock2-LockUtil:888sn
2022-04-11 16:02:58.091 bit [Thread-98] INFO  c.enmonster.bit.controller.testlock.LockEnterImpl.run:69 - l自动清除LockUti:BIT:LOCK:DAMAGE:SN:888sn
2022-04-11 16:02:58.121 bit [Thread-99] INFO  c.e.bit.config.redislock.aspect.RedisLockAspect.around:40 - 代理加锁成功:BIT:LOCK:DAMAGE:SN:666sn
2022-04-11 16:02:58.122 bit [Thread-99] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:666sn0
2022-04-11 16:02:58.122 bit [Thread-99] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:666sn1
2022-04-11 16:02:58.122 bit [Thread-99] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:666sn2
2022-04-11 16:02:58.122 bit [Thread-99] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:666sn3
2022-04-11 16:02:58.122 bit [Thread-99] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:666sn4
2022-04-11 16:02:58.122 bit [Thread-99] INFO  c.e.bit.controller.testlock.LockProcessImpl.process:25 - 测试加锁:666sn5
2022-04-11 16:02:58.142 bit [Thread-99] INFO  c.e.bit.config.redislock.aspect.RedisLockAspect.around:48 - 代理解锁:BIT:LOCK:DAMAGE:SN:666sn
2022-04-11 16:02:58.142 bit [Thread-99] INFO  c.enmonster.bit.controller.testlock.LockEnterImpl.run:83 - lock3-LockUtil:666sn
2022-04-11 16:02:58.142 bit [Thread-99] INFO  c.enmonster.bit.controller.testlock.LockEnterImpl.run:85 - 自动清除LockUti:BIT:LOCK:DAMAGE:SN:666sn

四、原理分析

1、ThreadLocal

        线程缓存是java提供的绑定当前线程的存储空间，因此在任意方法进行ThreadLocal 的设置，后续只要属于当前线程的方法都可以取到这个值。

        首先通过它的set方法分析

    public void set(T value) {
        Thread t = Thread.currentThread();
        //获取当前线程为键对应的ThreadLocalMap
        ThreadLocalMap map = getMap(t);
        //将当前ThreadLocal对象作为基础，业务值设置到ThreadLocalMap维护的数组中
        if (map != null)
            map.set(this, value);
        else
            createMap(t, value);
    }

    void createMap(Thread t, T firstValue) {
        //创建当前线程的ThreadLocalMap
        t.threadLocals = new ThreadLocalMap(this, firstValue);
    }

        ThreadLocalMap(ThreadLocal firstKey, Object firstValue) {
            //ThreadLocalMap维护了一个数组，这是因为线程的缓存值可能有多个，许多第三方框架都在使用
            table = new Entry[INITIAL_CAPACITY];
            int i = firstKey.threadLocalHashCode & (INITIAL_CAPACITY - 1);
            table[i] = new Entry(firstKey, firstValue);
            size = 1;
            setThreshold(INITIAL_CAPACITY);
        }

        private void set(ThreadLocal key, Object value) {
            Entry[] tab = table;
            int len = tab.length;
            //通过hasn值与数组长度取&获取下标
            int i = key.threadLocalHashCode & (len-1);

            //将业务值设置到数组中
            for (Entry e = tab[i];
                 e != null;
                 e = tab[i = nextIndex(i, len)]) {
                ThreadLocal k = e.get();
                if (k == key) {
                    e.value = value;
                    return;
                }

                if (k == null) {
                    replaceStaleEntry(key, value, i);
                    return;
                }
            }
            tab[i] = new Entry(key, value);
            int sz = ++size;
            if (!cleanSomeSlots(i, sz) && sz >= threshold)
                rehash();
        }
    

        接着通过get方法分析

    public T get() {
        //获取当前线程
        Thread t = Thread.currentThread();
        //获取当前线程为键对应的ThreadLocalMap 
        ThreadLocalMap map = getMap(t);
        if (map != null) {
            //将当前ThreaadLocal对象传入getEntry方法，获取线程缓存的值
            ThreadLocalMap.Entry e = map.getEntry(this);
            if (e != null) {
                @SuppressWarnings("unchecked")
                T result = (T)e.value;
                return result;
            }
        }
        return setInitialValue();
    }

        private Entry getEntry(ThreadLocal key) {
            //根据对象的hash值与存储数组进行&，获取存储值的下标
            int i = key.threadLocalHashCode & (table.length - 1);
            Entry e = table[i];
            if (e != null && e.get() == key)
                return e;
            else
                return getEntryAfterMiss(key, i, e);
        }

        用完记得remove！由于ThreadLocalMap的Entry是虚引用，线程如果不销毁不会被回收，用完就进行remove会避免内存泄漏风险。

    public void remove() {
         ThreadLocalMap m = getMap(Thread.currentThread());
         if (m != null)
             m.remove(this);
     }

        private void remove(ThreadLocal key) {
            Entry[] tab = table;
            int len = tab.length;
            int i = key.threadLocalHashCode & (len-1);
            for (Entry e = tab[i];
                 e != null;
                 e = tab[i = nextIndex(i, len)]) {
                if (e.get() == key) {
                    //将虚引用置为null
                    e.clear();
                    //清理数组
                    expungeStaleEntry(i);
                    return;
                }
            }
        }

        private int expungeStaleEntry(int staleSlot) {
            Entry[] tab = table;
            int len = tab.length;

            //将该下标对象置为null，便于gc回收
            tab[staleSlot].value = null;
            tab[staleSlot] = null;
            size--;

            Entry e;
            int i;
            //遍历该下标之后所有不为空的ThreadLocal对象
            for (i = nextIndex(staleSlot, len);
                 (e = tab[i]) != null;
                 i = nextIndex(i, len)) {
                ThreadLocal k = e.get();
                if (k == null) {
                    //如果该ThreadLocal实例的虚引用已经被销毁，将该位置的ThreadLocal置为null
                    e.value = null;
                    tab[i] = null;
                    size--;
                } else {
                    int h = k.threadLocalHashCode & (len - 1);
                    if (h != i) {
                        tab[i] = null;
                        while (tab[h] != null)
                            h = nextIndex(h, len);
                        tab[h] = e;
                    }
                }
            }
            return i;
        }

2、AOP

        对于动态代理可以说是老生常谈了，这里就不进行描述了，做个字节码反编译给大家看看代理类的实际模样吧。

        可以看到代理类继承自Proxy，并且将LockProcessImpl 的方法编织成了接口方法，再由代理类实现接口方法。最终调用invoke方法，invoke方法在会通过反射获取到原始方法要执行的代码，并且进行方法增强。

        总结起来就是AOP将注解下的类方法进行包装，切面的代码将业务方法包在中间进行增强执行。

import com.enmonster.bit.controller.testlock.LockProcessImpl;
import com.enmonster.bit.entity.responsibility.MacSnChainDTO;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;

public final class LockProcessImpl extends Proxy implements LockProcessImpl {
  private static Method m1;
  
  private static Method m8;
  
  private static Method m3;
  
  private static Method m2;
  
  private static Method m6;
  
  private static Method m5;
  
  private static Method m7;
  
  private static Method m9;
  
  private static Method m0;
  
  private static Method m4;
  
  public LockProcessImpl(InvocationHandler paramInvocationHandler) {
    super(paramInvocationHandler);
  }
  
  public final boolean equals(Object paramObject) {
    try {
      return ((Boolean)this.h.invoke(this, m1, new Object[] { paramObject })).booleanValue();
    } catch (Error|RuntimeException error) {
      throw null;
    } catch (Throwable throwable) {
      throw new UndeclaredThrowableException(throwable);
    } 
  }
  
  public final void notify() {
    try {
      this.h.invoke(this, m8, null);
      return;
    } catch (Error|RuntimeException error) {
      throw null;
    } catch (Throwable throwable) {
      throw new UndeclaredThrowableException(throwable);
    } 
  }
  
  public final void process(MacSnChainDTO paramMacSnChainDTO) {
    try {
      this.h.invoke(this, m3, new Object[] { paramMacSnChainDTO });
      return;
    } catch (Error|RuntimeException error) {
      throw null;
    } catch (Throwable throwable) {
      throw new UndeclaredThrowableException(throwable);
    } 
  }
  
  public final String toString() {
    try {
      return (String)this.h.invoke(this, m2, null);
    } catch (Error|RuntimeException error) {
      throw null;
    } catch (Throwable throwable) {
      throw new UndeclaredThrowableException(throwable);
    } 
  }
  
  public final void wait(long paramLong) throws InterruptedException {
    try {
      this.h.invoke(this, m6, new Object[] { Long.valueOf(paramLong) });
      return;
    } catch (Error|RuntimeException|InterruptedException error) {
      throw null;
    } catch (Throwable throwable) {
      throw new UndeclaredThrowableException(throwable);
    } 
  }
  
  public final void wait(long paramLong, int paramInt) throws InterruptedException {
    try {
      this.h.invoke(this, m5, new Object[] { Long.valueOf(paramLong), Integer.valueOf(paramInt) });
      return;
    } catch (Error|RuntimeException|InterruptedException error) {
      throw null;
    } catch (Throwable throwable) {
      throw new UndeclaredThrowableException(throwable);
    } 
  }
  
  public final Class getClass() {
    try {
      return (Class)this.h.invoke(this, m7, null);
    } catch (Error|RuntimeException error) {
      throw null;
    } catch (Throwable throwable) {
      throw new UndeclaredThrowableException(throwable);
    } 
  }
  
  public final void notifyAll() {
    try {
      this.h.invoke(this, m9, null);
      return;
    } catch (Error|RuntimeException error) {
      throw null;
    } catch (Throwable throwable) {
      throw new UndeclaredThrowableException(throwable);
    } 
  }
  
  public final int hashCode() {
    try {
      return ((Integer)this.h.invoke(this, m0, null)).intValue();
    } catch (Error|RuntimeException error) {
      throw null;
    } catch (Throwable throwable) {
      throw new UndeclaredThrowableException(throwable);
    } 
  }
  
  public final void wait() throws InterruptedException {
    try {
      this.h.invoke(this, m4, null);
      return;
    } catch (Error|RuntimeException|InterruptedException error) {
      throw null;
    } catch (Throwable throwable) {
      throw new UndeclaredThrowableException(throwable);
    } 
  }
  
  static {
    try {
      m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] { Class.forName("java.lang.Object") });
      m8 = Class.forName("com.enmonster.bit.controller.testlock.LockProcessImpl").getMethod("notify", new Class[0]);
      m3 = Class.forName("com.enmonster.bit.controller.testlock.LockProcessImpl").getMethod("process", new Class[] { Class.forName("com.enmonster.bit.entity.responsibility.MacSnChainDTO") });
      m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
      m6 = Class.forName("com.enmonster.bit.controller.testlock.LockProcessImpl").getMethod("wait", new Class[] { long.class });
      m5 = Class.forName("com.enmonster.bit.controller.testlock.LockProcessImpl").getMethod("wait", new Class[] { long.class, int.class });
      m7 = Class.forName("com.enmonster.bit.controller.testlock.LockProcessImpl").getMethod("getClass", new Class[0]);
      m9 = Class.forName("com.enmonster.bit.controller.testlock.LockProcessImpl").getMethod("notifyAll", new Class[0]);
      m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
      m4 = Class.forName("com.enmonster.bit.controller.testlock.LockProcessImpl").getMethod("wait", new Class[0]);
      return;
    } catch (NoSuchMethodException noSuchMethodException) {
      throw new NoSuchMethodError(noSuchMethodException.getMessage());
    } catch (ClassNotFoundException classNotFoundException) {
      throw new NoClassDefFoundError(classNotFoundException.getMessage());
    } 
  }
}