如何优雅处理重复请求/并发请求?
JAVA葵花宝典
共 10314字,需浏览 21分钟
· 2021-06-08
前言
黑客拦截了请求,重放; 前端/客户端因为某些原因请求重复发送了,或者用户在很短的时间内重复点击了; 网关重发; ……
![](https://filescdn.proginn.com/44934ca133e56493bcfb7eb1a070a3dc/ed8fafbf671d6c52d15ec7e3d33ac3a4.webp)
利用唯一请求编号去重
String KEY = "REQ12343456788";//请求唯一编号
long expireTime = 1000;// 1000毫秒过期,1000ms内的重复请求会认为重复
long expireAt = System.currentTimeMillis() + expireTime;
String val = "expireAt@" + expireAt;
//redis key还存在的话要就认为请求是重复的
Boolean firstSet = stringRedisTemplate.execute((RedisCallback<Boolean>) connection -> connection.set(KEY.getBytes(), val.getBytes(), Expiration.milliseconds(expireTime), RedisStringCommands.SetOption.SET_IF_ABSENT));
final boolean isConsiderDup;
if (firstSet != null && firstSet) {// 第一次访问
isConsiderDup = false;
} else {// redis值已存在,认为是重复了
isConsiderDup = true;
![](https://filescdn.proginn.com/44934ca133e56493bcfb7eb1a070a3dc/ed8fafbf671d6c52d15ec7e3d33ac3a4.webp)
业务参数去重
String KEY = "dedup:U="+userId + "M=" + method + "P=" + reqParam;
1、计算请求参数的摘要作为参数标识
2、继续优化,考虑剔除部分时间因子
//两个请求一样,但是请求时间差一秒
String req = "{\n" +
"\"requestTime\" :\"20190101120001\",\n" +
"\"requestValue\" :\"1000\",\n" +
"\"requestKey\" :\"key\"\n" +
"}";
String req2 = "{\n" +
"\"requestTime\" :\"20190101120002\",\n" +
"\"requestValue\" :\"1000\",\n" +
"\"requestKey\" :\"key\"\n" +
"}";
![](https://filescdn.proginn.com/44934ca133e56493bcfb7eb1a070a3dc/ed8fafbf671d6c52d15ec7e3d33ac3a4.webp)
请求去重工具类的代码落地
public class ReqDedupHelper {
/**
*
* @param reqJSON 请求的参数,这里通常是JSON
* @param excludeKeys 请求参数里面要去除哪些字段再求摘要
* @return 去除参数的MD5摘要
*/
public String dedupParamMD5(final String reqJSON, String... excludeKeys) {
String decreptParam = reqJSON;
TreeMap paramTreeMap = JSON.parseObject(decreptParam, TreeMap.class);
if (excludeKeys!=null) {
List<String> dedupExcludeKeys = Arrays.asList(excludeKeys);
if (!dedupExcludeKeys.isEmpty()) {
for (String dedupExcludeKey : dedupExcludeKeys) {
paramTreeMap.remove(dedupExcludeKey);
}
}
}
String paramTreeMapJSON = JSON.toJSONString(paramTreeMap);
String md5deDupParam = jdkMD5(paramTreeMapJSON);
log.debug("md5deDupParam = {}, excludeKeys = {} {}", md5deDupParam, Arrays.deepToString(excludeKeys), paramTreeMapJSON);
return md5deDupParam;
}
private static String jdkMD5(String src) {
String res = null;
try {
MessageDigest messageDigest = MessageDigest.getInstance("MD5");
byte[] mdBytes = messageDigest.digest(src.getBytes());
res = DatatypeConverter.printHexBinary(mdBytes);
} catch (Exception e) {
log.error("",e);
}
return res;
}
}
public static void main(String[] args) {
//两个请求一样,但是请求时间差一秒
String req = "{\n" +
"\"requestTime\" :\"20190101120001\",\n" +
"\"requestValue\" :\"1000\",\n" +
"\"requestKey\" :\"key\"\n" +
"}";
String req2 = "{\n" +
"\"requestTime\" :\"20190101120002\",\n" +
"\"requestValue\" :\"1000\",\n" +
"\"requestKey\" :\"key\"\n" +
"}";
//全参数比对,所以两个参数MD5不同
String dedupMD5 = new ReqDedupHelper().dedupParamMD5(req);
String dedupMD52 = new ReqDedupHelper().dedupParamMD5(req2);
System.out.println("req1MD5 = "+ dedupMD5+" , req2MD5="+dedupMD52);
//去除时间参数比对,MD5相同
String dedupMD53 = new ReqDedupHelper().dedupParamMD5(req,"requestTime");
String dedupMD54 = new ReqDedupHelper().dedupParamMD5(req2,"requestTime");
System.out.println("req1MD5 = "+ dedupMD53+" , req2MD5="+dedupMD54);
}
req1MD5 = 9E054D36439EBDD0604C5E65EB5C8267 , req2MD5=A2D20BAC78551C4CA09BEF97FE468A3F
req1MD5 = C2A36FED15128E9E878583CAAAFEFDE9 , req2MD5=C2A36FED15128E9E878583CAAAFEFDE9
一开始两个参数由于 requestTime 是不同的,所以求去重参数摘要的时候可以发现两个值是不一样的; 第二次调用的时候,去除了 requestTime 再求摘要(第二个参数中传入了”requestTime”),则发现两个摘要是一样的,符合预期。
String userId= "12345678";//用户
String method = "pay";//接口名
String dedupMD5 = new ReqDedupHelper().dedupParamMD5(req,"requestTime");//计算请求参数摘要,其中剔除里面请求时间的干扰
String KEY = "dedup:U=" + userId + "M=" + method + "P=" + dedupMD5;
long expireTime = 1000;// 1000毫秒过期,1000ms内的重复请求会认为重复
long expireAt = System.currentTimeMillis() + expireTime;
String val = "expireAt@" + expireAt;
// NOTE:直接SETNX不支持带过期时间,所以设置+过期不是原子操作,极端情况下可能设置了就不过期了,后面相同请求可能会误以为需要去重,所以这里使用底层API,保证SETNX+过期时间是原子操作
Boolean firstSet = stringRedisTemplate.execute((RedisCallback<Boolean>) connection -> connection.set(KEY.getBytes(), val.getBytes(), Expiration.milliseconds(expireTime),
RedisStringCommands.SetOption.SET_IF_ABSENT));
final boolean isConsiderDup;
if (firstSet != null && firstSet) {
isConsiderDup = false;
} else {
isConsiderDup = true;
}
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作者:Jaskey Lam 来源: http://jaskey.github.io/blog/2020/05/19/handle-duplicate-request/
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