高并发下的幂等性问题
高并发下的幂等性问题
1.什么是幂等性
幂等（idempotent、idempotence）是一个数学与计算机学概念，常见于抽象代数中。在编程中.一个幂等操作的特点是其任意多次执行所产生的影响均与一次执行的影响相同。幂等函数，或幂等方法，是指可以使用相同参数重复执行，并能获得相同结果的函数。这些函数不会影响系统状态，也不用担心重复执行会对系统造成改变。例如，“getUsername()和setTrue()”函数就是一个幂等函数. 更复杂的操作幂等保证是利用唯一交易号(流水号)实现. 我的理解：幂等就是一个操作，不论执行多少次，产生的效果和返回的结果都是一样的 。
而在我们实际开发中用到最多的是接口这一块，随着前后端分离的趋势化，接口开发是不可避免的，这里面就涉及到幂等性问题比如：
（1）订单接口, 不能多次创建订单
（2）支付接口, 重复支付同一笔订单只能扣一次钱
（3）支付宝回调接口, 可能会多次回调, 必须处理重复回调
（4）普通表单提交接口, 因为网络超时等原因多次点击提交, 只能成功一次
常用的解决方法：
（1）唯一索引 – 防止新增脏数据
（2）token机制 – 防止页面重复提交
（3）悲观锁 – 获取数据的时候加锁(锁表或锁行)
（4）乐观锁 – 基于版本号version实现, 在更新数据那一刻校验数据
（5）分布式锁 – redis(jedis、redisson)或zookeeper实现
（6）状态机 – 状态变更, 更新数据时判断状态
悲观锁和乐观锁可以看下面链接：
https://blog.csdn.net/qq_34136709/article/details/107911749
我们这里先学习token机制，即通过redis + token机制实现接口幂等性校验
2.实现思路
为需要保证幂等性的每一次请求创建一个唯一标识token, 先获取token, 并将此token存入redis, 请求接口时, 将此token放到header或者作为请求参数请求接口, 后端接口判断redis中是否存在此token:
（1）如果存在, 正常处理业务逻辑, 并从redis中删除此token, 那么, 如果是重复请求, 由于token已被删除, 则不能通过校验, 返回请勿重复操作提示
（2）如果不存在, 说明参数不合法或者是重复请求, 返回提示即可
3.代码如下：
pom文件:
<dependency>
<groupId>redis.clients</groupId>
<artifactId>jedis</artifactId>
<version>2.9.0</version>
</dependency>
JedisUtil:
package com.cp.springbootone.util;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
/**
* @author ChengPeng
* @create 2020-07-31 11:19
*/
@Component
@Slf4j
public class JedisUtil {
@Autowired(required = false)
private JedisPool jedisPool;
private Jedis getJedis(){
return jedisPool.getResource();
}
/**
* 设值
*
* @param key
* @param value
* @return
*/
public String set(String key, String value) {
Jedis jedis = null;
try {
jedis = getJedis();
return jedis.set(key, value);
} catch (Exception e) {
log.error("set key:{} value:{} error", key, value, e);
return null;
} finally {
close(jedis);
}
}
/**
* 设值
*
* @param key
* @param value
* @param expireTime 过期时间, 单位: s
* @return
*/
public String set(String key, String value, int expireTime) {
Jedis jedis = null;
try {
jedis = getJedis();
return jedis.setex(key, expireTime, value);
} catch (Exception e) {
log.error("set key:{} value:{} expireTime:{} error", key, value, expireTime, e);
return null;
} finally {
close(jedis);
}
}
/**
* 设值
*
* @param key
* @param value
* @return
*/
public Long setnx(String key, String value) {
Jedis jedis = null;
try {
jedis = getJedis();
return jedis.setnx(key, value);
} catch (Exception e) {
log.error("set key:{} value:{} error", key, value, e);
return null;
} finally {
close(jedis);
}
}
/**
* 取值
*
* @param key
* @return
*/
public String get(String key) {
Jedis jedis = null;
try {
jedis = getJedis();
return jedis.get(key);
} catch (Exception e) {
log.error("get key:{} error", key, e);
return null;
} finally {
close(jedis);
}
}
/**
* 删除key
*
* @param key
* @return
*/
public Long del(String key) {
Jedis jedis = null;
try {
jedis = getJedis();
return jedis.del(key.getBytes());
} catch (Exception e) {
log.error("del key:{} error", key, e);
return null;
} finally {
close(jedis);
}
}
/**
* 判断key是否存在
*
* @param key
* @return
*/
public Boolean exists(String key) {
Jedis jedis = null;
try {
jedis = getJedis();
return jedis.exists(key.getBytes());
} catch (Exception e) {
log.error("exists key:{} error", key, e);
return null;
} finally {
close(jedis);
}
}
/**
* 设值key过期时间
*
* @param key
* @param expireTime 过期时间, 单位: s
* @return
*/
public Long expire(String key, int expireTime) {
Jedis jedis = null;
try {
jedis = getJedis();
return jedis.expire(key.getBytes(), expireTime);
} catch (Exception e) {
log.error("expire key:{} error", key, e);
return null;
} finally {
close(jedis);
}
}
/**
* 获取剩余时间
*
* @param key
* @return
*/
public Long ttl(String key) {
Jedis jedis = null;
try {
jedis = getJedis();
return jedis.ttl(key);
} catch (Exception e) {
log.error("ttl key:{} error", key, e);
return null;
} finally {
close(jedis);
}
}
private void close(Jedis jedis) {
if (null != jedis) {
jedis.close();
}
}
}
自定义注解@ApiIdempotent
package com.cp.springbootone.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* @author ChengPeng
* @create 2020-07-31 15:09
* 在需要保证 接口幂等性的controller的方法上使用此注解
*/
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface ApiIdempotent {
}
ApiIdempotentInterceptor拦截器
package com.cp.springbootone.interceptor;
import com.cp.springbootone.annotation.ApiIdempotent;
import com.cp.springbootone.service.TokenService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.lang.reflect.Method;
/**
* @author ChengPeng
* @create 2020-07-31 15:13
* 接口幂等性拦截器
*/
public class ApiIdempotentInterceptor implements HandlerInterceptor {
@Autowired
private TokenService tokenService;
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
if (!(handler instanceof HandlerMethod)) {
return true;
}
HandlerMethod handlerMethod = (HandlerMethod) handler;
Method method = handlerMethod.getMethod();
ApiIdempotent methodAnnotation = method.getAnnotation(ApiIdempotent.class);
if (methodAnnotation != null) {
check(request);// 幂等性校验, 校验通过则放行, 校验失败则抛出异常, 并通过统一异常处理返回友好提示
}
return true;
}
private void check(HttpServletRequest request) {
tokenService.checkToken(request);
}
@Override
public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
}
@Override
public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
}
}
TokenServiceImpl
package com.cp.springbootone.service.impl;
import com.cp.springbootone.common.Constant;
import com.cp.springbootone.common.ResponseCode;
import com.cp.springbootone.common.ServerResponse;
import com.cp.springbootone.exception.ServiceException;
import com.cp.springbootone.service.TokenService;
import com.cp.springbootone.util.JedisUtil;
import com.cp.springbootone.util.RandomUtil;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.text.StrBuilder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import javax.servlet.http.HttpServletRequest;
/**
* @author ChengPeng
* @create 2020-07-31 15:34
*/
@Service
public class TokenServiceImpl implements TokenService {
private static final String TOKEN_NAME = "token";
@Autowired
private JedisUtil jedisUtil;
@Override
public ServerResponse createToken() {
String str = RandomUtil.UUID32();
StrBuilder token = new StrBuilder();
token.append(Constant.Redis.TOKEN_PREFIX).append(str);
jedisUtil.set(token.toString(), token.toString(), Constant.Redis.EXPIRE_TIME_HOUR);
return ServerResponse.success(token.toString());
}
@Override
public void checkToken(HttpServletRequest request) {
String token = request.getHeader(TOKEN_NAME);
if (StringUtils.isBlank(token)) {// header中不存在token
token = request.getParameter(TOKEN_NAME);
if (StringUtils.isBlank(token)) {// parameter中也不存在token
throw new ServiceException(ResponseCode.ILLEGAL_ARGUMENT.getMsg());
}
}
if (!jedisUtil.exists(token)) {
throw new ServiceException(ResponseCode.REPETITIVE_OPERATION.getMsg());
}
Long del = jedisUtil.del(token);
if (del <= 0) {
throw new ServiceException(ResponseCode.REPETITIVE_OPERATION.getMsg());
}
}
}
Application
package com.cp.springbootone;
import com.cp.springbootone.interceptor.AccessLimitInterceptor;
import com.cp.springbootone.interceptor.ApiIdempotentInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.web.cors.CorsConfiguration;
import org.springframework.web.cors.UrlBasedCorsConfigurationSource;
import org.springframework.web.filter.CorsFilter;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
@SpringBootApplication
@MapperScan("com.cp.springbootone.mapper")
@EnableScheduling
public class SpringbootoneApplication extends WebMvcConfigurerAdapter {
public static void main(String[] args) {
SpringApplication.run(SpringbootoneApplication.class, args);
}
/**
* 跨域
*/
@Bean
public CorsFilter corsFilter(){
final UrlBasedCorsConfigurationSource urlBasedCorsConfigurationSource = new UrlBasedCorsConfigurationSource();
final CorsConfiguration corsConfiguration = new CorsConfiguration();
corsConfiguration.setAllowCredentials(true);
corsConfiguration.addAllowedOrigin("*");
corsConfiguration.addAllowedHeader("*");
corsConfiguration.addAllowedMethod("*");
urlBasedCorsConfigurationSource.registerCorsConfiguration("/**", corsConfiguration);
return new CorsFilter(urlBasedCorsConfigurationSource);
}
@Override
public void addInterceptors(InterceptorRegistry registry) {
// 接口幂等性拦截器
registry.addInterceptor(apiIdempotentInterceptor());
// 接口防刷限流拦截器
registry.addInterceptor(accessLimitInterceptor());
super.addInterceptors(registry);
}
@Bean
public ApiIdempotentInterceptor apiIdempotentInterceptor() {
return new ApiIdempotentInterceptor();
}
@Bean
public AccessLimitInterceptor accessLimitInterceptor() {
return new AccessLimitInterceptor();
}
}
4.测试验证
获取token的控制器TokenController
package com.cp.springbootone.controller;
import com.cp.springbootone.common.ServerResponse;
import com.cp.springbootone.service.TokenService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
/**
* @author ChengPeng
* @create 2020-07-31 17:18
*/
@RestController
@RequestMapping("/token")
public class TokenController {
@Autowired
private TokenService tokenService;
@GetMapping
public ServerResponse token() {
return tokenService.createToken();
}
}
TestController, 注意@ApiIdempotent注解, 在需要幂等性校验的方法上声明此注解即可, 不需要校验的无影响
package com.cp.springbootone.controller;
import com.cp.springbootone.annotation.ApiIdempotent;
import com.cp.springbootone.common.ServerResponse;
import com.cp.springbootone.service.TestService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
/**
* @author ChengPeng
* @create 2020-07-31 17:20
*/
@RestController
@RequestMapping("/test")
@Slf4j
public class TestController {
@Autowired
private TestService testService;
@ApiIdempotent
@PostMapping("testIdempotence")
public ServerResponse testIdempotence() {
return testService.testIdempotence();
}
}
主要代码如上，后期出个视频，完成代码后期补上。
我们启动好项目，请求token的接口，存到redis里面
redis管理工具链接如下：
链接：https://share.weiyun.com/QIYcYzD4 密码：y33quv
我们用jmeter进行测试
第一次是成功的，后面的线程会提示重复操作，还有其他的方法，后期再说，希望对大家有帮助，欢迎关注和评论，谢谢！