springcloud如何用Redlock實現(xiàn)分布式鎖

第springcloud如何用Redlock實現(xiàn)分布式鎖目錄一、redlock簡介二、怎么用java使用redlock三、參考資料之前寫過一篇文章《如何在springcloud分布式系統(tǒng)中實現(xiàn)分布式鎖？》，由于自己僅僅是閱讀了相關的書籍，和查閱了相關的資料，就認為那樣的是可行的。那篇文章實現(xiàn)的大概思路是用setNx命令和setEx配合使用。setNx是一個耗時操作，因為它需要查詢這個鍵是否存在，就算redis的百萬的qps，在高并發(fā)的場景下，這種操作也是有問題的。關于redis實現(xiàn)分布式鎖，redis官方推薦使用redlock。

一、redlock簡介

在不同進程需要互斥地訪問共享資源時，分布式鎖是一種非常有用的技術手段。實現(xiàn)高效的分布式鎖有三個屬性需要考慮：

安全屬性：互斥，不管什么時候，只有一個客戶端持有鎖

效率屬性A:不會死鎖

效率屬性B：容錯，只要大多數(shù)redis節(jié)點能夠正常工作，客戶端端都能獲取和釋放鎖。

Redlock是redis官方提出的實現(xiàn)分布式鎖管理器的算法。這個算法會比一般的普通方法更加安全可靠。關于這個算法的討論可以看下官方文檔。

二、怎么用java使用redlock

在pom文件引入redis和redisson依賴：

!--redis--

dependency

groupIdorg.springframework.boot/groupId

artifactIdspring-boot-starter-data-redis/artifactId

/dependency

!--redisson--

dependency

groupIdorg.redisson/groupId

artifactIdredisson/artifactId

version3.3.2/version

/dependency

AquiredLockWorker接口類，，主要是用于獲取鎖后需要處理的邏輯：

*Createdbyfangzhipengon2017/4/5.

*獲取鎖后需要處理的邏輯

publicinterfaceAquiredLockWorkerT{

TinvokeAfterLockAquire()throwsException;

}

DistributedLocker獲取鎖管理類：

*Createdbyfangzhipengon2017/4/5.

*獲取鎖管理類

publicinterfaceDistributedLocker{

*獲取鎖

*@paramresourceName鎖的名稱

*@paramworker獲取鎖后的處理類

*@paramT

*@return處理完具體的業(yè)務邏輯要返回的數(shù)據

*@throwsUnableToAquireLockException

*@throwsException

TTlock(StringresourceName,AquiredLockWorkerTworker)throwsUnableToAquireLockException,Exception;

TTlock(StringresourceName,AquiredLockWorkerTworker,intlockTime)throwsUnableToAquireLockException,Exception;

}

UnableToAquireLockException，不能獲取鎖的異常類：

*Createdbyfangzhipengon2017/4/5.

*異常類

publicclassUnableToAquireLockExceptionextendsRuntimeException{

publicUnableToAquireLockException(){

publicUnableToAquireLockException(Stringmessage){

super(message);

publicUnableToAquireLockException(Stringmessage,Throwablecause){

super(message,cause);

}

RedissonConnector連接類：

*Createdbyfangzhipengon2017/4/5.

*獲取RedissonClient連接類

@Component

publicclassRedissonConnector{

RedissonClientredisson;

@PostConstruct

publicvoidinit(){

redisson=Redisson.create();

publicRedissonClientgetClient(){

returnredisson;

}

RedisLocker類，實現(xiàn)了DistributedLocker：

importorg.redisson.api.RLock;

importorg.redisson.api.RedissonClient;

importorg.springframework.beans.factory.annotation.Autowired;

importorg.springframework.stereotype.Component;

importjava.util.concurrent.TimeUnit;

*Createdbyfangzhipengon2017/4/5.

@Component

publicclassRedisLockerimplementsDistributedLocker{

privatefinalstaticStringLOCKER_PREFIX="lock:";

@Autowired

RedissonConnectorredissonConnector;

@Override

publicTTlock(StringresourceName,AquiredLockWorkerTworker)throwsInterruptedException,UnableToAquireLockException,Exception{

returnlock(resourceName,worker,100);

@Override

publicTTlock(StringresourceName,AquiredLockWorkerTworker,intlockTime)throwsUnableToAquireLockException,Exception{

RedissonClientredisson=redissonConnector.getClient();

RLocklock=redisson.getLock(LOCKER_PREFIX+resourceName);

//Waitfor100secondssecondsandautomaticallyunlockitafterlockTimeseconds

booleansuccess=lock.tryLock(100,lockTime,TimeUnit.SECONDS);

if(success){

try{

returnworker.invokeAfterLockAquire();

}finally{

lock.unlock();

thrownewUnableToAquireLockException();

}

測試類：

@Autowired

RedisLockerdistributedLocker;

@RequestMapping(value="/redlock")

publicStringtestRedlock()throwsException{

CountDownLatchstartSignal=newCountDownLatch(1);

CountDownLatchdoneSignal=newCountDownLatch(5);

for(inti=0;i++i){//createandstartthreads

newThread(newWorker(startSignal,doneSignal)).start();

startSignal.countDown();//letallthreadsproceed

doneSignal.await();

System.out.println("Allprocessorsdone.Shutdownconnection");

return"redlock";

classWorkerimplementsRunnable{

privatefinalCountDownLatchstartSignal;

privatefinalCountDownLatchdoneSignal;

Worker(CountDownLatchstartSignal,CountDownLatchdoneSignal){

this.startSignal=startSignal;

this.doneSignal=doneSignal;

publicvoidrun(){

try{

startSignal.await();

distributedLocker.lock("test",newAquiredLockWorkerObject(){

@Override

publicObjectinvokeAfterLockAquire(){

doTask();

returnnull;

}catch(Exceptione){

voiddoTask(){

System.out.println(Thread.currentThread().getName()+"start");

Randomrandom=newRandom();

int_int=random.nextInt(200);

System.out.println(Thread.currentThread().getName()+"sleep"+_int+"millis");

try{

Thread.sleep(_int);

}catch(InterruptedExceptione){

e.printStackTrace();

System.out.println(Thread.currentThread().getName()+"end");

doneSignal.countDown();

}

運行測試類：

Thread-48start

Thread-48sleep99millis

Thread-48end

Thread-49start

Thread-49sleep118millis

Thread-49end

Thread-52start

Thread-52sleep141millis

Thread-52end

Thread-50start

Thread-50sleep28millis

Thread-50end