Spring-cloud-gateway-RetryFilterBug

This repository is reproducing the bug of Retry filter in spring cloud gateway

Build and Run

• Build project:

./gradlew clean build

• Run application via docker-compose:
  • default(with console logs):

  docker-compose --build
  

  • silent mode:

  docker-compose up -d --remove-orphan --build
  

Reproducing bug

Configuration contains only 1 route: /canary. Retry filter configuration for the route:

- name: Retry
  args:
    retries: 3
    statuses: BAD_REQUEST
    backoff:
      firstBackoff: 1000ms
      maxBackoff: 1000ms
      factor: 2
      basedOnPreviousValue: false

Now, execute the following command

curl http://localhost:8080/canary?code=400

You'll see that the filter is working on specified status. Next execute

curl http://localhost:8080/canary?code=500

You'll see that filter is working, but the series is not specified in configuration. The only solution is to specify series as null:

- name: Retry
  args:
    retries: 3
    statuses: BAD_REQUEST
    series: null
    backoff:
      firstBackoff: 1000ms
      maxBackoff: 1000ms
      factor: 2
      basedOnPreviousValue: false

The reason of the bug

RetryGatewayFilterFactory is configured so, that if the response code is not the code that specified in configuration and it not null, the factory will try to retry by series.

if (!retryableStatusCode && statusCode != null) 
    retryableStatusCode = retryConfig.getSeries().stream()
	.anyMatch(series -> statusCode.series().equals(series));
}

If the series is not specified in configuration it will be trying the default series which is Series.SERVER_ERROR (5xx).

public static class RetryConfig implements HasRouteId {

    /*other fields*/

    private List<Series> series = toList(Series.SERVER_ERROR);

    /*other code*/
}

So even the series is not specified in configuration the filter will always check the series.

Possible solution

I think the better way to fix the bug is to initialize series with empty list.

public static class RetryConfig implements HasRouteId {

    /*other fields*/

    private List<Series> series = Collections.emptyList();

    /*other code*/
}

In that case the filter will not check series that was not specified by user but only the status.