生产级幂等解决方案

ゞ浴缸里的玫瑰 2022-01-20 06:43 202阅读 0赞

之前写过一篇幂等的文章，但是仅仅只是思路，在生产环境肯定还是不能够用的。恰巧同事最近在讨论如何做幂等。那么如何设计幂等能够达到生产可用呢？请看下面代码：

## 幂等处理接口： ##

public interface IdempotentProcessor {
    
        /**
         * 处理幂等执行代码块
         * 
         * @param optType    the opt type
         * @param optId      the opt id
         * @param initStatus the init status
         * @param expireMs   the expire ms
         * @return the status enum
         */
        StatusEnum process(String optType, String optId, StatusEnum initStatus, long expireMs);
    
        /**
         * 提交幂等
         * @param optType the opt type
         * @param optId   the opt id
         * @return the boolean
         */
        boolean confirm(String optType, String optId);
    
        /**
         * 
         * 取消幂等
         * @param optType the opt type
         * @param optId   the opt id
         * @return the boolean
         */
        boolean cancel(String optType, String optId);
    
    }
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那么大家看到如上接口设计，会发现当执行process方法时执行幂等且还需要 confim一次,同时可以调用cancel取消幂等。为什么，因为如果在方法执行之前幂等了后续方法执行失败则出大事了。所以需要confirm、cancel两个方法保证最终成功和失败（画外音：此类设计有点TCC事务有木有？）

## 幂等实现类 ##

public class ItemProcessor implements IdempotentProcessor {
    
        private static final String CACHE_KEY = "dew:idempotent:item:";
    
        @Override
        public StatusEnum process(String optType, String optId, StatusEnum initStatus, long expireMs) {
            if (Dew.cluster.cache.setnx(CACHE_KEY + optType + ":" + optId, initStatus.toString(), expireMs / 1000)) {
                // 设置成功，表示之前不存在
                return StatusEnum.NOT_EXIST;
            } else {
                // 设置不成功，表示之前存在，返回存在的值
                String status = Dew.cluster.cache.get(CACHE_KEY + optType + ":" + optId);
                if (status == null || status.isEmpty()) {
                    // 设置成功，表示之前不存在
                    return StatusEnum.NOT_EXIST;
                } else {
                    return StatusEnum.valueOf(status);
                }
            }
        }
    
        @Override
        public boolean confirm(String optType, String optId) {
            long ttl = Dew.cluster.cache.ttl(CACHE_KEY + optType + ":" + optId);
            if (ttl > 0) {
                Dew.cluster.cache.setex(CACHE_KEY + optType + ":" + optId, StatusEnum.CONFIRMED.toString(), ttl);
            }
            return true;
        }
    
        @Override
        public boolean cancel(String optType, String optId) {
            Dew.cluster.cache.del(CACHE_KEY + optType + ":" + optId);
            return true;
        }
    
    }
    复制代码

## 幂等拦截器 ##

public class IdempotentHandlerInterceptor extends HandlerInterceptorAdapter {
    
        private DewIdempotentConfig dewIdempotentConfig;
    
        /**
         * Instantiates a new Idempotent handler interceptor.
         *
         * @param dewIdempotentConfig the dew idempotent config
         */
        public IdempotentHandlerInterceptor(DewIdempotentConfig dewIdempotentConfig) {
            this.dewIdempotentConfig = dewIdempotentConfig;
        }
    
        @Override
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
            Idempotent idempotent = ((HandlerMethod) handler).getMethod().getAnnotation(Idempotent.class);
            if (idempotent == null) {
                return super.preHandle(request, response, handler);
            }
            // 参数设置
            String optType = "[" + request.getMethod() + "]" + Dew.Info.name + "/" + request.getRequestURI();
            String optIdFlag = StringUtils.isEmpty(idempotent.optIdFlag()) ? dewIdempotentConfig.getDefaultOptIdFlag() : idempotent.optIdFlag();
            String optId = request.getHeader(optIdFlag);
            if (StringUtils.isEmpty(optId)) {
                optId = request.getParameter(optIdFlag);
            }
            if (StringUtils.isEmpty(optId)) {
                // optId不存在，表示忽略幂等检查，强制执行
                return super.preHandle(request, response, handler);
            }
            if (!DewIdempotent.existOptTypeInfo(optType)) {
                long expireMs = idempotent.expireMs() == -1 ? dewIdempotentConfig.getDefaultExpireMs() : idempotent.expireMs();
                boolean needConfirm = idempotent.needConfirm();
                StrategyEnum strategy = idempotent.strategy() == StrategyEnum.AUTO ? dewIdempotentConfig.getDefaultStrategy() : idempotent.strategy();
                DewIdempotent.initOptTypeInfo(optType, needConfirm, expireMs, strategy);
            }
            switch (DewIdempotent.process(optType, optId)) {
                case NOT_EXIST:
                    return super.preHandle(request, response, handler);
                case UN_CONFIRM:
                    ErrorController.error(request, response, 409,
                            "The last operation was still going on, please wait.", IdempotentException.class.getName());
                    return false;
                case CONFIRMED:
                    ErrorController.error(request, response, 423,
                            "Resources have been processed, can't repeat the request.", IdempotentException.class.getName());
                    return false;
                default:
                    return false;
            }
        }
    
    }
    复制代码

## 测试用例 ##

### 测试场景一 ###

第一次请求幂等失败手动取消幂等，第二次幂等成功

**代码：**

@GetMapping(value = "manual-confirm")
        @Idempotent(expireMs = 5000)
        public Resp<String> testManualConfirm(@RequestParam("str") String str) {
            try {
                if ("dew-test1".equals(str)){
                    throw new RuntimeException("处理幂等失败");
                }
                DewIdempotent.confirm();
            } catch (Exception e) {
                DewIdempotent.cancel();
                return Resp.serverError(str + "处理幂等失败");
            }
            return Resp.success(str);
        }
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@Test
    public void testConfirm() throws IOException, InterruptedException {
        //幂等唯一键值
        //
        HashMap<String, String> header = new HashMap<String, String>() {
            {
                put(DewIdempotentConfig.DEFAULT_OPT_ID_FLAG, "0001");
            }
        };
        //字符串等于dew-test1幂等失败
        Resp<String> error = Resp.generic($.http.get(urlPre + "manual-confirm?str=dew-test1", header), String.class);
        System.out.println("幂等失败 [errorCode=" + error.getCode() + "-errorMsg=" + error.getMessage() + "]");
        //字符串等于dew-test2幂等成功
        Resp<String> success = Resp.generic($.http.get(urlPre + "manual-confirm?str=dew-test2", header), String.class);
        System.out.println("幂等成功 [code=" + success.getCode() + "-body=" + success.getBody() + "]");
    }
    复制代码

**结果：**

幂等失败 [errorCode=500-errorMsg=dew-test1处理幂等失败]
    幂等成功 [code=200-body=dew-test2]
    复制代码

### 测试场景二 ###

第一次请求幂等成功手动提交confim，第二次幂等失败

**代码：**

@GetMapping(value = "manual-confirm")
    @Idempotent(expireMs = 5000)
    public Resp<String> testManualConfirm(@RequestParam("str") String str) {
        try {
            DewIdempotent.confirm();
        } catch (Exception e) {
            DewIdempotent.cancel();
            return Resp.serverError(str + "处理幂等失败");
        }
        return Resp.success(str);
    }
    复制代码

@Test
    public void testConfirm() throws IOException, InterruptedException {
        //幂等唯一键值
        //
        HashMap<String, String> header = new HashMap<String, String>() {
            {
                put(DewIdempotentConfig.DEFAULT_OPT_ID_FLAG, "0001");
            }
        };
        //字符串等于dew-test1幂等成功
        Resp<String> success = Resp.generic($.http.get(urlPre + "manual-confirm?str=dew-test1", header), String.class);
        System.out.println("幂等成功 [code=" + success.getCode() + "-body=" + success.getBody() + "]");
        Thread.sleep(500);
        //字符串等于dew-test2幂等失败
        Resp<String> error = Resp.generic($.http.get(urlPre + "manual-confirm?str=dew-test2", header), String.class);
        System.out.println("幂等失败 [errorCode=" + error.getCode() + "-errorMsg=" + error.getMessage() + "]");
    }
    复制代码

**结果：**

幂等成功 [code=200-body=dew-test1]
    2019-04-23 00:14:17.123 ERROR 8600 --- [nio-8080-exec-2] ms.dew.core.web.error.ErrorController    : Request [GET-/idempotent/manual-confirm] 169.254.156.20 , error 423 : Resources have been processed, can't repeat the request. 幂等失败 [errorCode=423-errorMsg=[]Resources have been processed, can't repeat the request.]
    复制代码

# 最后 #

此代码及思路的项目名为dew且是微服务一站式解决方案，提供：架构指南、容器优先/兼容Spring Cloud与Istio的框架、最佳实践及Devops标准化流程。 [dew.ms][]

源代码github地址：[github.com/gudaoxuri/d…][github.com_gudaoxuri_d]

各位朋友可以给这位大佬的项目star一波

[dew.ms]: https://link.juejin.im?target=http%3A%2F%2Fdew.ms%2F
[github.com_gudaoxuri_d]: https://link.juejin.im?target=https%3A%2F%2Fgithub.com%2Fgudaoxuri%2Fdew