使用重试和回退机制确保 Spring 微服务中的 API 弹性

本文介绍: 在当今的数字环境中，应用程序严重依赖外部 HTTP/REST API来实现各种功能。这些 API 通常会编排复杂的内部和外部 API 调用网络。这创建了一个依赖网络。因此，当依赖的 API 发生故障或停机时，面向主要应用程序的 API 需要熟练、优雅地处理这些中断。鉴于此，本文探讨了Spr in g 微服务中重试机制和回退方法的实现。具体来说，它强调了这些策略如何显着增强 API 集成可靠性并显着改善用户体验。

在当今的数字环境中，应用程序严重依赖外部 HTTP/REST API来实现各种功能。这些 API 通常会编排复杂的内部和外部 API 调用网络。这创建了一个依赖网络。因此，当依赖的 API 发生故障或停机时，面向主要应用程序的 API 需要熟练、优雅地处理这些中断。鉴于此，本文探讨了Spr in g 微服务中重试机制和回退方法的实现。具体来说，它强调了这些策略如何显着增强 API 集成可靠性并显着改善用户体验。

使用依赖于其他服务的 API 来成功执行的移动和 We b 应用程序面临着独特的挑战。例如，对依赖 API 的调用可能会因各种原因而失败，包括网络问题、超时、内部服务器错误或计划停机。因此，此类故障可能会损害用户体验、破坏关键功能并导致数据不一致。因此，实施策略来妥善处理这些故障对于维护系统完整性至关重要。

作为主要解决方案，重试机制用于处理暂时性错误和临时问题。通过自动重新尝试 API 调用，此机制通常可以解决与短暂网络故障或临时服务器不可用相关的问题。重要的是，区分适合重试的场景（例如网络超时）和重试可能无效甚至有害的场景（例如业务逻辑异常或数据验证错误）至关重要。

常见的方法包括：

此外，这两种方法都应该附带最大重试限制，以防止无限循环。此外，监控和记录每次重试尝试对于将来的分析和系统优化也很重要。

我们可以通过两种方式来实现重试和回退方法。


@Override
@Retry(name = "SOFT_PULL", fallbackMethod = "performSoftPull_Fallback")
public CreditBureauReportResponse performSoftPull(SoftPullParams softPullParams, ErrorsI error) {
    CreditBureauReportResponse result = null;
    try {
        Date dt = new Date();
        logger.info("UnderwritingServiceImpl::performSoftPull method call at :" + dt.toString() + ", for loan acct id:" + softPullParams.getUserLoanAccountId());
        CreditBureauReportRequest request = this.getCreditBureauReportRequest(softPullParams);
        RestTemplate restTemplate = this.externalApiRestTemplateFactory.getRestTemplate("SOFT_PULL", error);
        HttpHeaders headers = this.getHttpHeaders(softPullParams);
        HttpEntity<CreditBureauReportRequest> entity = new HttpEntity<>(request, headers);
        long startTime = System.currentTimeMillis();
        String uwServiceEndPoint = "/transaction";
        String callUrl = String.format("%s%s", appConfig.getUnderwritingTransactionApiPrefix(), uwServiceEndPoint);
        ResponseEntity<CreditBureauReportResponse> responseEntity = restTemplate.exchange(callUrl, HttpMethod.POST, entity, CreditBureauReportResponse.class);
        result = responseEntity.getBody();
        long endTime = System.currentTimeMillis();
        long timeDifference = endTime - startTime;
        logger.info("Time taken for API call SOFT_PULL/performSoftPull call 1: " + timeDifference);
    } catch (HttpClientErrorException exception) {
        logger.error("HttpClientErrorException occurred while calling SOFT_PULL API, response string: " + exception.getResponseBodyAsString());
        throw exception;
    } catch (HttpStatusCodeException exception) {
        logger.error("HttpStatusCodeException occurred while calling SOFT_PULL API, response string: " + exception.getResponseBodyAsString());
        throw exception;
    } catch (Exception ex) {
        logger.error("Error occurred in performSoftPull. Detail error:", ex);
        throw ex;
    }
    return result;
}

resilience4j.retry:  configs:    default:      maxRetryAttempts: 3      waitDuration: 100    externalPartner:      maxRetryAttempts: 2      waitDuration: 1000  instances:    SOFT_PULL:      baseConfig: externalPartner


public CreditBureauReportResponse performSoftPull_Fallback(SoftPullParams softPullParams, ErrorsI error, Exception extPartnerException) {
    logger.info("UnderwritingServiceImpl::performSoftPull_Fallback - fallback , method called for soft pull api call");
    CreditBureauReportResponse creditBureauReportResponse = null;
    String loanAcctId = softPullParams.getUserLoanAccountId();
    ApplicantCoBorrowerIdsMapping applicantCoBorrowerIdsMapping = this.uwCoBorrowerRepository.getApplicantCoBorrowerIdsMapping(loanAcctId);
    try {
        boolean result = this.partnerServiceExceptionRepository.savePartnerServiceException(applicantCoBorrowerIdsMapping.getApplicantUserId(),
                applicantCoBorrowerIdsMapping.getLoanId(), PartnerService.SOFT_PULL.getValue(), "GDS", null);

        if (!result) {
            logger.error("UnderwritingServiceImpl::performSoftPull_Fallback - Unable to save entry in the partner service exception table.");
        }
        LoanSubStatus loanSubStatus = LoanSubStatus.PARTNER_API_ERROR;
        result = this.loanUwRepository.saveLoanStatus(applicantCoBorrowerIdsMapping.getApplicantUserId(), applicantCoBorrowerIdsMapping.getLoanId(),
                IcwLoanStatus.INITIATED.getValue(), loanSubStatus.getName(), "Partner Service Down", null);
        if (!result) {
            logger.error("UnderwritingServiceImpl::performSoftPull_Fallback - Unable to update loan status, sub status when partner service is down.");
        }
    } catch (Exception ex) {
        logger.error("UnderwritingServiceImpl::performSoftPull_Fallback - An error occurred while calling softPullExtPartnerFallbackService, detail error:", ex);
    }
    creditBureauReportResponse = new CreditBureauReportResponse();
    UnderwritingApiError underwritingApiError = new UnderwritingApiError();
    underwritingApiError.setCode("IC-EXT-PARTNER-1001");
    underwritingApiError.setDescription("Soft Pull API error");
    List<UnderwritingApiError> underwritingApiErrors = new ArrayList<>();
    underwritingApiErrors.add(underwritingApiError);
    creditBureauReportResponse.setErrors(underwritingApiErrors);
    return creditBureauReportResponse;
}


@Retryable(retryFor = {HttpClientErrorException.class, HttpStatusCodeException.class, Exception.class}, maxAttempts = 2, backoff = @Backoff(delay = 100))
public CreditBureauReportResponse performSoftPull(SoftPullParams softPullParams, ErrorsI error) {


@Recover
public CreditBureauReportResponse fallbackForPerformSoftPull(HttpClientErrorException ex, SoftPullParams softPullParams, ErrorsI error) {
  // Fallback Implementation
}

@Recover
public CreditBureauReportResponse fallbackForPerformSoftPull(HttpStatusCodeException ex, SoftPullParams softPullParams, ErrorsI error) {
  // Fallback Implementation
}

@Recover
public CreditBureauReportResponse fallbackForPerformSoftPull(Exception ex, SoftPullParams softPullParams, ErrorsI error) {
  // Fallback Implementation
}