Redis原理和高可用场景实践总结（三）

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.dao.DataAccessException;
import org.springframework.data.redis.connection.RedisConnection;
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.serializer.StringRedisSerializer;
/**
 * 分布式锁
 * 性能待测试
 * @author lzhcode
 *
 */
public class RedisLock {
    private static Logger logger = LoggerFactory.getLogger(RedisLock.class);
      private RedisTemplate redisTemplate;
      private static final int DEFAULT_ACQUIRY_RESOLUTION_MILLIS = 100;
      /**
       * Lock key path.
       */
      private String lockKey;
      /**
       * 锁超时时间，防止线程在入锁以后，无限的执行等待
       */
      private int expireMsecs = 60 * 1000;
      /**
       * 锁等待时间，防止线程饥饿
       */
      private int timeoutMsecs = 10 * 1000;
      private volatile boolean locked = false;
      /**
       * Detailed constructor with default acquire timeout 10000 msecs and lock expiration of 60000 msecs.
       *
       * @param lockKey lock key (ex. account:1, ...)
       */
      public RedisLock(RedisTemplate redisTemplate, String lockKey) {
          this.redisTemplate = redisTemplate;
          this.lockKey = lockKey + "_lock";
      }
      /**
       * Detailed constructor with default lock expiration of 60000 msecs.
       *
       */
      public RedisLock(RedisTemplate redisTemplate, String lockKey, int timeoutMsecs) {
          this(redisTemplate, lockKey);
          this.timeoutMsecs = timeoutMsecs;
      }
      /**
       * Detailed constructor.
       *
       */
      public RedisLock(RedisTemplate redisTemplate, String lockKey, int timeoutMsecs, int expireMsecs) {
          this(redisTemplate, lockKey, timeoutMsecs);
          this.expireMsecs = expireMsecs;
      }
      /**
       * @return lock key
       */
      public String getLockKey() {
          return lockKey;
      }
      private String get(final String key) {
          Object obj = null;
          try {
              obj = redisTemplate.execute(new RedisCallback<Object>() {
                  @Override
                  public Object doInRedis(RedisConnection connection) throws DataAccessException {
                      StringRedisSerializer serializer = new StringRedisSerializer();
                      byte[] data = connection.get(serializer.serialize(key));
                      connection.close();
                      if (data == null) {
                          return null;
                      }
                      return serializer.deserialize(data);
                  }
              });
          } catch (Exception e) {
              logger.error("get redis error, key : {}", key);
          }
          return obj != null ? obj.toString() : null;
      }
      private boolean setNX(final String key, final String value) {
          Object obj = null;
          try {
              obj = redisTemplate.execute(new RedisCallback<Object>() {
                  @Override
                  public Object doInRedis(RedisConnection connection) throws DataAccessException {
                      StringRedisSerializer serializer = new StringRedisSerializer();
                      Boolean success = connection.setNX(serializer.serialize(key), serializer.serialize(value));
                      connection.close();
                      return success;
                  }
              });
          } catch (Exception e) {
              logger.error("setNX redis error, key : {}", key);
          }
          return obj != null ? (Boolean) obj : false;
      }
      private String getSet(final String key, final String value) {
          Object obj = null;
          try {
              obj = redisTemplate.execute(new RedisCallback<Object>() {
                  @Override
                  public Object doInRedis(RedisConnection connection) throws DataAccessException {
                      StringRedisSerializer serializer = new StringRedisSerializer();
                      byte[] ret = connection.getSet(serializer.serialize(key), serializer.serialize(value));
                      connection.close();
                      return serializer.deserialize(ret);
                  }
              });
          } catch (Exception e) {
              logger.error("setNX redis error, key : {}", key);
          }
          return obj != null ? (String) obj : null;
      }
      /**
       * 获得 lock.
       * 实现思路: 主要是使用了redis 的setnx命令,缓存了锁.
       * reids缓存的key是锁的key,所有的共享, value是锁的到期时间(注意:这里把过期时间放在value了,没有时间上设置其超时时间)
       * 执行过程:
       * 1.通过setnx尝试设置某个key的值,成功(当前没有这个锁)则返回,成功获得锁
       * 2.锁已经存在则获取锁的到期时间,和当前时间比较,超时的话,则设置新的值
       *
       * @return true if lock is acquired, false acquire timeouted
       * @throws InterruptedException in case of thread interruption
       */
      public   boolean lock() throws InterruptedException {
          int timeout = timeoutMsecs;
          while (timeout >= 0) {
              long expires = System.currentTimeMillis() + expireMsecs + 1;
              String expiresStr = String.valueOf(expires); //锁到期时间
              if (this.setNX(lockKey, expiresStr)) {
                  // lock acquired
                  locked = true;
                  return true;
              }
              String currentValueStr = this.get(lockKey); //redis里的时间
              if (currentValueStr != null && Long.parseLong(currentValueStr) < System.currentTimeMillis()) {
                  //判断是否为空，不为空的情况下，如果被其他线程设置了值，则第二个条件判断是过不去的
                  // lock is expired
                  String oldValueStr = this.getSet(lockKey, expiresStr);
                  //获取上一个锁到期时间，并设置现在的锁到期时间，
                  //只有一个线程才能获取上一个线上的设置时间，因为jedis.getSet是同步的
                  if (oldValueStr != null && oldValueStr.equals(currentValueStr)) {
                      //防止误删（覆盖，因为key是相同的）了他人的锁——这里达不到效果，这里值会被覆盖，但是因为什么相差了很少的时间，所以可以接受
                      //[分布式的情况下]:如过这个时候，多个线程恰好都到了这里，但是只有一个线程的设置值和当前值相同，他才有权利获取锁
                      // lock acquired
                      locked = true;
                      return true;
                  }
              }
              timeout -= DEFAULT_ACQUIRY_RESOLUTION_MILLIS;
              /*
                  延迟100 毫秒,  这里使用随机时间可能会好一点,可以防止饥饿进程的出现,即,当同时到达多个进程,
                  只会有一个进程获得锁,其他的都用同样的频率进行尝试,后面有来了一些进行,也以同样的频率申请锁,这将可能导致前面来的锁得不到满足.
                  使用随机的等待时间可以一定程度上保证公平性
               */
              Thread.sleep(DEFAULT_ACQUIRY_RESOLUTION_MILLIS);
          }
          return false;
      }
      /**
       * Acqurired lock release.
       */
      public   void unlock() {
          if (locked) {
              redisTemplate.delete(lockKey);
              locked = false;
          }
      }
}

redis-cli -p 6500 config set protected-mode no

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface DuplicateSubmit {
}

import lombok.extern.slf4j.Slf4j;
import org.aspectj.lang.ProceedingJoinPoint;
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.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import javax.servlet.http.HttpServletRequest;
import java.lang.reflect.Method;
import java.util.concurrent.TimeUnit;
@Aspect
@Component
@Order(-2)
@Slf4j
public class DuplicateSubmitInteceptor {
    @Autowired
    private RedisUtils redisDomainService;
    @Pointcut("within(com.controller..*)")
    public void doubleCheckCut() {
    }
    @Around("doubleCheckCut()")
    public Object around(ProceedingJoinPoint pjp) throws Throwable {
        Method method = ((MethodSignature) pjp.getSignature()).getMethod();
        DuplicateSubmit duplicateSubmit = method.getAnnotation(DuplicateSubmit.class);
        if (null != duplicateSubmit) {
            HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest();
            String uri = request.getRequestURI();
            Long orgId = UserContextHolder.getUser().getUserId();
            if (null == orgId) {
                throw new ServerException(ErrorCode.USER_INFO_ERROR);
            }
            String value = Long.toString(System.currentTimeMillis());
            try {
                boolean dobuleCheck =
                        redisDomainService.setIfAbsent(String.format(RedisKeyEnum.DOUBLE_REQUEST.getCode(), uri, orgId),
                                value,
                                RedisKeyEnum.DOUBLE_REQUEST.getTime().intValue(), TimeUnit.SECONDS);
                if (!dobuleCheck) {
                    log.error("======>表单重复提交限制出错...{}");
                    throw new ServerException(ErrorCode.DOUBLE_REQUEST_ERROR);
                }
                Object proceed = pjp.proceed();
                return proceed;
            } catch (Exception e) {
                log.error("======>表单重复提交限制出错...{}", e);
                throw e;
            } finally {
                String o = redisDomainService.getString(String.format(RedisKeyEnum.DOUBLE_REQUEST.getCode(), uri,
                        orgId));
                if (null != o) {
                    redisDomainService.unlock(String.format(RedisKeyEnum.DOUBLE_REQUEST.getCode(), uri, orgId), value);
                }
            }
        }
        return pjp.proceed();
    }
}