redis 分布式锁-原创手记-慕课网

最近抽空优化了之前已有的redis分布式锁，主要用于解决高并发的问题，比如抢红包，多个人同时操作红包库存，当在库存只剩下1个的时候，一个人的减库存的操作事务没提交，另一个人的查库存操作刚好同步执行，这样就会出现很尴尬的事情，1个红包会被2个人抢走，这个时候，我们就要依托锁，将请求入口锁住，当然锁有很多种方式，这边就记录一下比较好用的redis分布式锁。

方式有很多setNX 、set、incr等等，setNX只要通过逻辑防止死锁就可以了

直接上代码：

public boolean keyLock(final String key, final long keepMin) {

boolean obj = false;

try {

obj = (boolean) redisTemplateSerializable.execute(new RedisCallback<Object>() {

@Override

public Object doInRedis(RedisConnection connection)

throws DataAccessException {

try{

Long incr = connection.incr(key.getBytes());

if(incr == 1){

connection.setEx(key.getBytes(), keepMin, incr.toString().getBytes());

return true;

}else{

Long ttl = connection.ttl(key.getBytes());

if(ttl == -1){

//设置失败,重新设置过期时间

connection.setEx(key.getBytes(), keepMin, incr.toString().getBytes());

return true;

}

}catch (Exception e) {

logger.error("加锁异常", e);

connection.del(key.getBytes());

return true;

}

return false;

}

});

}catch (Exception e) {

logger.error(e.getMessage());

}

return obj;

}

注解

package com.tp.soft.common.interceptor;

import java.lang.annotation.Documented;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

import java.util.concurrent.TimeUnit;

/**

redis锁注解

@author taopbr/>*/

@Retention(RetentionPolicy.RUNTIME)

@Target({ ElementType.METHOD })br/>@Documented

public @interface RedisLock {

String lockName() default ""; // 锁名

int retryTimes() default 0; // 重试次数

long retryWait() default 200; // 重试等待时间,单位 : ms

int keeyMinTime() default 1; //锁自动失效时间 1秒

}

aop

package com.tp.soft.aop.redis;

import java.lang.reflect.Method;

import java.util.HashMap;

import java.util.Map;

import javax.annotation.Resource;

import org.apache.commons.lang.StringUtils;

import org.aspectj.lang.ProceedingJoinPoint;

import org.aspectj.lang.Signature;

import org.aspectj.lang.annotation.Around;

import org.aspectj.lang.annotation.Aspect;

import org.aspectj.lang.annotation.Pointcut;

import org.aspectj.lang.reflect.MethodSignature;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import org.springframework.core.LocalVariableTableParameterNameDiscoverer;

import org.springframework.expression.ExpressionParser;

import org.springframework.expression.spel.standard.SpelExpressionParser;

import org.springframework.expression.spel.support.StandardEvaluationContext;

import org.springframework.stereotype.Component;

import cn.hutool.core.lang.Assert;

import com.tp.soft.common.interceptor.Cacheable;

import com.tp.soft.common.interceptor.RedisLock;

import com.tp.soft.redis.RedisCacheSvc;br/>@Aspect

@Component

public class RedisLockAop {

private static final Logger log = LoggerFactory.getLogger(RedisLockAop.class);

private static final String LOCK_NAME = "lockName";

private static final String RETRY_TIMES = "retryTimes";

private static final String RETRY_WAIT = "retryWait";

private static final String KEEP_MIN_TIME = "keepMinTime";br/>@Resource

private RedisCacheSvc redisCacheSvc;br/>@Pointcut("@annotation(com.tp.soft.common.interceptor.RedisLock)")

public void redisLockAspect() {br/>}

@Around("redisLockAspect()")

public Object lockAroundAction(ProceedingJoinPoint pjp) throws Throwable {

Method method = returnMethod(pjp);

Map<String, Object> annotationArgs = this.getAnnotationArgs(pjp);

String lockPrefix = (String) annotationArgs.get(LOCK_NAME);

Assert.notNull(lockPrefix, "分布式,锁名不能为空");

int retryTimes = (int) annotationArgs.get(RETRY_TIMES);

long retryWait = (long) annotationArgs.get(RETRY_WAIT);

int keepMinTime = (int) annotationArgs.get(KEEP_MIN_TIME);

String keyName = parseKey(lockPrefix, method, pjp.getArgs());

// 获取redis锁,防止死锁

boolean keyLock = redisCacheSvc.keyLock(keyName, keepMinTime);

if(keyLock){

//执行主程序

return pjp.proceed();

}else{

if(retryTimes <= 0){

log.info(String.format("{%s}已经被锁, 不重试", keyName));

throw new RuntimeException(String.format("{%s}已经被锁, 不重试", keyName));

}

int failCount = 1;

while (failCount <= retryTimes) {

// 等待指定时间ms

try {

Thread.sleep(retryWait);

} catch (InterruptedException e) {

e.printStackTrace();

}

if (redisCacheSvc.keyLock(keyName, keepMinTime)) {

// 执行主逻辑

return pjp.proceed();

} else {

log.info(String.format("{%s}已经被锁, 正在重试[ %s/%s ],重试间隔{%s}毫秒", keyName, failCount, retryTimes, retryWait));

failCount++;

}

throw new RuntimeException("系统繁忙, 请稍等再试");

}

/**

获取锁参数

@param proceeding

@return

private Map<String, Object> getAnnotationArgs(ProceedingJoinPoint proceeding) {

Class target = proceeding.getTarget().getClass();

Method[] methods = target.getMethods();

String methodName = proceeding.getSignature().getName();

for (Method method : methods) {

if (method.getName().equals(methodName)) {

Map<String, Object> result = new HashMap<String, Object>();

RedisLock redisLock = method.getAnnotation(RedisLock.class);

result.put(LOCK_NAME, redisLock.lockName());

result.put(RETRY_TIMES, redisLock.retryTimes());

result.put(RETRY_WAIT, redisLock.retryWait());

result.put(KEEP_MIN_TIME, redisLock.keeyMinTime());

return result;

}

return null;

}

private Method returnMethod(ProceedingJoinPoint pjp)

throws NoSuchMethodException {

Signature signature = pjp.getSignature();

Class<? extends Object> cls = pjp.getTarget().getClass();

MethodSignature methodSignature = (MethodSignature) signature;

Method targetMethod = methodSignature.getMethod();

Method method = cls.getDeclaredMethod(signature.getName(),

targetMethod.getParameterTypes());

return method;

}

/**

获取缓存的key key 定义在注解上，支持SPEL表达式

@param pjp

@return

private String parseKey(String key, Method method, Object[] args) {

// 获取被拦截方法参数名列表(使用Spring支持类库)

LocalVariableTableParameterNameDiscoverer u = new LocalVariableTableParameterNameDiscoverer();

String[] paraNameArr = u.getParameterNames(method);

// 使用SPEL进行key的解析

ExpressionParser parser = new SpelExpressionParser();

// SPEL上下文

StandardEvaluationContext context = new StandardEvaluationContext();

// 把方法参数放入SPEL上下文中

for (int i = 0; i < paraNameArr.length; i++) {

context.setVariable(paraNameArr[i], args[i]);

}

return parser.parseExpression(key).getValue(context, String.class);

}

搭建完成后直接在需要锁住的接口上注解

@RedisLock(lockName="'lock_'+#tbbId",retryTimes=5)

模拟高并发测试

for (int i = 0; i < 2; i++) {

threadPoolTaskExecutor.execute(new StartTaskThread(redisCacheSvc, i, threadPoolTaskExecutor));

}

redis 分布式锁

效果就是这样了

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