redis 分布式锁

Posted 2021-01-28

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

觉得还不错的朋友 后台回复“Java”领取资料 一起交流