Angular-HTTP拦截器重试具有特定错误状态的请求？

Question

我正在尝试使用拦截器来处理http错误并重试特殊的错误状态，在我的情况下为状态码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)
            )
        })
      )
  }

但是它不起作用，但是当我retry()以这种方式使用时，它就可以完美地工作

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

Answer 1

我出于自己的兴趣采用了您的方法，并对其进行了扩展。

首先是创建一种自定义运算符：

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，您可以根据此运算符构造拦截器，如下所示：

@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;
}

您可以看到它在这次闪电战中发挥了作用