分布式锁实现限流
1.限流锁的应用场景
同一时间接口访问量巨大，如秒杀，需要进行限流。
2.实现思路
用 CURRENT_LIMIT_+ 类名+方法名作为redis的key, value作为访问秒杀接口的人数。
用redis的计数器统计访问人数，每新增一个访问请求，计数器+1，当人数超过上限，提示服务忙，秒杀接口处理完之后，计数器-1。
3.主要组成
Dcl：限流注解，自定义锁注解，然后给需要限流的方法加上此注解
DistributedCurrentLimit：限流接口
RedisDistributedCurrentLimit：限流实现类
DistributedCurrentLimitAspect：切面类【核心】
自定义锁注解，利用切面给所有加注解的方法加分布式锁进行限流。
4.关键代码分析：
DistributedCurrentLimitAspect：用redis计时器算人头，人头达到上限就返回服务正忙
@Around("@annotation(com.nascent.ecrp.mall.common.distribute.Dcl)")
public Object distributedLock(ProceedingJoinPoint proceedingJoinPoint) throws Throwable {
if (request == null) {
return proceedingJoinPoint.proceed();
}
MethodSignature methodSignature = (MethodSignature) proceedingJoinPoint.getSignature();
Method method = methodSignature.getMethod();
// 用CURRENT_LIMIT_+ 类名+方法名作为redis的key,统计调用此方法的用户数
String lockKey = "CURRENT_LIMIT_" + method.getDeclaringClass().getName() + "." + method.getName();
Dcl distributedKey = method.getAnnotation(Dcl.class);
// 解析缓存key的后缀
int keyIndex = distributedKey.keyIndex();
String suffixKey = "";
if (keyIndex > -1) {
Object[] args = proceedingJoinPoint.getArgs();
suffixKey += "_" + args[keyIndex];
}
lockKey += suffixKey;
try {
// 每进来一个，redis的计数器+1
Long incr = currentLimit.incr(lockKey);
// 计数器数 > MAX_LIMIT，抛出异常，用户就不能继续访问接口了
if (incr > MAX_LIMIT) {
// currentLimit.decr(lockKey);
throw new WmDefinitelyRuntimeException("前方道路拥挤，请稍后再试");
}
return proceedingJoinPoint.proceed();
} catch (Throwable e) {
throw new WmDefinitelyRuntimeException(e);
} finally {
currentLimit.decr(lockKey);
}
}
3.全部代码
Dcl
/**
* 限流
*/
@Documented
@Inherited
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Dcl {
/**
* 缓存key后缀参数所在位置
*
* @return 位置
*/
int keyIndex();
}
DistributedCurrentLimit
/**
* 分布式限流
*/
public interface DistributedCurrentLimit{
/**
* 队列加1
*/
Long incr(String lockKey);
/**
* 队列减一
*/
Long decr(String lockKey);
RedisDistributedCurrentLimit
/**
* redis 分布式锁
*/
@SuppressWarnings({"UnusedReturnValue", "NullableProblems", "unused", "RedundantThrows"})
@Component
public class RedisDistributedCurrentLimit implements DistributedCurrentLimit {
/**
* 缓存
*/
@Autowired
private RedisTemplate<String, Object> redisTemplate;
@Override
public Long incr(String lockKey) {
return redisTemplate.opsForValue().increment(lockKey);
}
@Override
public Long decr(String lockKey) {
return redisTemplate.opsForValue().decrement(lockKey);
}
}
DistributedCurrentLimitAspect
/**
* 用户操作锁Aspect
*/
@Aspect
@Component
@Order(-1)
public class DistributedCurrentLimitAspect {
/**
* 默认最大队列，暂时写死
*/
private static final Long MAX_LIMIT = 50L;
/**
* 分布式锁
*/
@Autowired
private RedisDistributedCurrentLimit currentLimit;
@Autowired
private HttpServletRequest request;
/**
* @param proceedingJoinPoint proceedingJoinPoint
*/
@Around("@annotation(com.nascent.ecrp.mall.common.distribute.Dcl)")
public Object distributedLock(ProceedingJoinPoint proceedingJoinPoint) throws Throwable {
if (request == null) {
return proceedingJoinPoint.proceed();
}
MethodSignature methodSignature = (MethodSignature) proceedingJoinPoint.getSignature();
Method method = methodSignature.getMethod();
String lockKey = "CURRENT_LIMIT_" + method.getDeclaringClass().getName() + "." + method.getName();
Dcl distributedKey = method.getAnnotation(Dcl.class);
// 解析缓存key的后缀
int keyIndex = distributedKey.keyIndex();
String suffixKey = "";
if (keyIndex > -1) {
Object[] args = proceedingJoinPoint.getArgs();
suffixKey += "_" + args[keyIndex];
}
lockKey += suffixKey;
try {
Long incr = currentLimit.incr(lockKey);
if (incr > MAX_LIMIT) {
// currentLimit.decr(lockKey);
throw new WmDefinitelyRuntimeException("前方道路拥挤，请稍后再试");
}
return proceedingJoinPoint.proceed();
} catch (Throwable e) {
throw new WmDefinitelyRuntimeException(e);
} finally {
currentLimit.decr(lockKey);
}
}
}
秒杀接口添加锁注解
/**
* 参与秒杀
*
* @return CommonResult
*/
@Dul
@Dcl(keyIndex = 0)
@Transactional(rollbackFor = Exception.class)
@Override
public CommonResult doSeckill(WmMarketingSeckillPostVo seckillPostVo) {
String checkResult = checkGoodsSeckillInfo(seckillPostVo.getSeckillOrderInfoList(),seckillPostVo.getShopId());
if(checkResult.equals(ErrorCode.SECKILL_ACTIVITY_UPDATE.getCode())){
return new CommonResult().setFailed().setCode(ErrorCode.SECKILL_ACTIVITY_UPDATE.getCode()).setMsg("活动状态已变更，请重新下单");
}
List<JSONObject> seckillOrderList = new ArrayList<>();
//下单校验
List<SecKillBuyInfo> buyInfos = new ArrayList<>();
SeckillOrderCheckRequest seckillOrderCheckRequest = new SeckillOrderCheckRequest();
seckillOrderCheckRequest.setCustomerId(getCustomerId());
seckillOrderCheckRequest.setShopId(seckillPostVo.getShopId());
for(WmMarketingSeckillPostVo.SeckillOrderInfo seckillOrderInfo : seckillPostVo.getSeckillOrderInfoList()){
SecKillBuyInfo secKillBuyInfo = new SecKillBuyInfo();
secKillBuyInfo.setActivityId(seckillOrderInfo.getMarketingGuid());
List<SeckillBuyGoodsInfo> seckillBuyGoodsInfos = new ArrayList<>();
SeckillBuyGoodsInfo seckillBuyGoodsInfo = new SeckillBuyGoodsInfo();
seckillBuyGoodsInfo.setGoodsId(seckillOrderInfo.getGoodsId());
seckillBuyGoodsInfo.setGoodsLibId(seckillOrderInfo.getGoodsLibId());
List<SeckillBuySkuInfo> seckillBuySkuInfos = new ArrayList<>();
SeckillBuySkuInfo seckillBuySkuInfo = new SeckillBuySkuInfo();
seckillBuySkuInfo.setGoodsSkuId(StringUtil.isBlank(seckillOrderInfo.getGoodsSkuId()) ? "0" : seckillOrderInfo.getGoodsSkuId());
seckillBuySkuInfo.setBuyCount(seckillOrderInfo.getGoodsNum());
seckillBuySkuInfos.add(seckillBuySkuInfo);
seckillBuyGoodsInfo.setSkuInfos(seckillBuySkuInfos);
seckillBuyGoodsInfos.add(seckillBuyGoodsInfo);
secKillBuyInfo.setGoodsList(seckillBuyGoodsInfos);
buyInfos.add(secKillBuyInfo);
}
seckillOrderCheckRequest.setBuyInfos(buyInfos);
seckillOrderCheckRequest.setGroupId(getGroupId());
SeckillOrderCheckResponse seckillOrderCheckResponse = OpenPlatformClient.exec(getGroupId(), seckillOrderCheckRequest);
log.info("【调用中台下单校验接口响应结果】seckillOrderCheckResponse="+JSON.toJSONString(seckillOrderCheckResponse));
if(!seckillOrderCheckResponse.success&&seckillOrderCheckResponse.getCode().equals("50402")){
log.info("【秒杀下单已达限购上限】");
return new CommonResult().setFailed().setCode("50402").setMsg("已达限购上限");
}
if(!seckillOrderCheckResponse.success&&seckillOrderCheckResponse.getCode().equals("50404")){
log.info("【秒杀剩余库存不足】");
return new CommonResult().setFailed().setCode("50404").setMsg("剩余库存不足");
}
if(!seckillOrderCheckResponse.success&&seckillOrderCheckResponse.getCode().equals("50005")){
log.info("【秒杀活动已结束】");
return new CommonResult().setFailed().setCode("50005").setMsg("活动已结束");
}
AssertUtil.assertTrue(seckillOrderCheckResponse.getSuccess()&&seckillOrderCheckResponse.getResult().isSeckillSuccess(),"秒杀活动校验失败");
Map<String,ActivitySeckillCheckInfo> activityCheckInfoMap = new HashMap<>();
for(ActivitySeckillCheckInfo activitySeckillCheckInfo : seckillOrderCheckResponse.getResult().getCheckInfos()){
Long goodsId = activitySeckillCheckInfo.getItemInfos().get(0).getGoodsId();
Long goodsLibId = activitySeckillCheckInfo.getItemInfos().get(0).getGoodsLibId();
String skuId = activitySeckillCheckInfo.getItemInfos().get(0).getSkuInfos().get(0).getSkuId();//无sku也会返回到sku级，skuid为0
activityCheckInfoMap.put(activitySeckillCheckInfo.getActivityId()+"_"+goodsLibId+"_"+goodsId+"_"+skuId,activitySeckillCheckInfo);
}
Map<String, ItemDetailsInfo> itemInfoMap = getGoodsInfos(seckillPostVo.getShopId(),seckillPostVo.getSeckillOrderInfoList());
Integer expireMinute = seckillOrderCheckResponse.getResult().getExpireMinute();
for(WmMarketingSeckillPostVo.SeckillOrderInfo seckillOrderInfo :seckillPostVo.getSeckillOrderInfoList()){
ItemDetailsInfo itemInfo = itemInfoMap.get(seckillOrderInfo.getGoodsId()+"_"+seckillOrderInfo.getGoodsLibId());
Long marketGuid = seckillOrderInfo.getMarketingGuid();
Long goodsId = seckillOrderInfo.getGoodsId();
Long goodsLibId = seckillOrderInfo.getGoodsLibId();
String goodsSkuId = seckillOrderInfo.getGoodsSkuId()==null?"0":seckillOrderInfo.getGoodsSkuId();//无sku也会返回到sku级，skuid为0
ActivitySeckillCheckInfo activitySeckillCheckInfo = activityCheckInfoMap.get(marketGuid+"_"+goodsLibId+"_"+goodsId+"_"+goodsSkuId);
String activityName = activitySeckillCheckInfo.getActivityName();
//秒杀价
BigDecimal price = itemInfo.getPrice();
for(ActivitySeckillCheckItemInfo activitySeckillCheckItemInfo : activitySeckillCheckInfo.getItemInfos()){
if(activitySeckillCheckItemInfo.getGoodsId().longValue() == seckillOrderInfo.getGoodsId().longValue() && activitySeckillCheckItemInfo.getGoodsLibId().longValue() == seckillOrderInfo.getGoodsLibId().longValue()){
for(ActivitySeckillCheckSkuInfo seckillCheckSkuInfo : activitySeckillCheckItemInfo.getSkuInfos()){
if(seckillCheckSkuInfo.getSkuId().equals("0")||seckillCheckSkuInfo.getSkuId().equals(seckillOrderInfo.getGoodsSkuId())){
price = seckillCheckSkuInfo.getPrice();
}
}
}
}
JSONObject orderJson = createOrderDetail(marketGuid,activityName,expireMinute,seckillOrderInfo.getGoodsNum(), goodsId, goodsSkuId, price, itemInfo);
seckillOrderList.add(orderJson);
}
return new CommonResult(seckillOrderList);
}