Angular - HTTP 拦截器重试具有特定错误状态的请求? [英] Angular - HTTP interceptor to retry requests with specific error status?

问题描述

我正在尝试使用拦截器来处理 http 错误并重试特殊错误状态，在我的例子中是状态代码 502.

I am trying to use an interceptor to handle http errors and retry for a special error status, in my case the status code 502.

intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(request)
      .pipe(
        retryWhen(errors => {
          return errors
            .pipe(
              mergeMap(error => (error.status === 502) ? throwError(error) : of(error)),
              take(2)
            )
        })
      )
  }

但它不起作用，而当我以这种方式使用 retry() 时，它工作得很好

But it's not working, whereas when I am using retry() in this fashion, it's working perfectly

intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(request)
      .pipe(
        retry(2),
        catchError((error: HttpErrorResponse) => {
          return throwError(error);
        })
      )
  }

推荐答案

出于自己的兴趣，我采用了您的方法并对其进行了一些扩展.

I took your approach and expanded it a little, out of own interest.

首先是创建一种自定义运算符:

The first would be to create a sort of custom operator:

import { timer, throwError, Observable } from 'rxjs';
import { mergeMap } from 'rxjs/operators';

export interface RetryParams {
  maxAttempts?: number;
  scalingDuration?: number;
  shouldRetry?: ({ status: number }) => boolean;
}

const defaultParams: RetryParams = {
  maxAttempts: 3,
  scalingDuration: 1000,
  shouldRetry: ({ status }) => status >= 400
}

export const genericRetryStrategy = (params: RetryParams = {}) => (attempts: Observable<any>) => attempts.pipe(
  mergeMap((error, i) => {
    const { maxAttempts, scalingDuration, shouldRetry } = { ...defaultParams, ...params }
    const retryAttempt = i + 1;
    // if maximum number of retries have been met
    // or response is a status code we don't wish to retry, throw error
    if (retryAttempt > maxAttempts || !shouldRetry(error)) {
      return throwError(error);
    }
    console.log(`Attempt ${retryAttempt}: retrying in ${retryAttempt * scalingDuration}ms`);
    // retry after 1s, 2s, etc...
    return timer(retryAttempt * scalingDuration);
  })
);

然后你可以基于这个操作符构造一个拦截器，如下所示:

You can then construct an interceptor based on this operator as follows:

@Injectable()
export class RetryInterceptor implements HttpInterceptor {
  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    const { shouldRetry } = this;
    return next.handle(request)
      .pipe(retryWhen(genericRetryStrategy({
        shouldRetry
      })));
  }

  private shouldRetry = (error) => error.status === 502;
}

您可以在在这次闪电战中看到它运行

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