Flexible retry library for Dio package. This is a next generation of an abandoned dio_retry package.
By default, the request will be retried only for appropriate retryable http statuses.
Also, it supports dynamic delay between retries.
Null Safety.

• Dio Smart Retry
  • Contents
  • Getting Started for Dio
  • Usage
  • Default retryable status codes list
  • Disable retry
  • Add extra retryable status codes
  • Override retryable statuses
  • Retry requests with multipart/form-data

1. Add package to pubspec.yaml: dio_smart_retry: ^5.0.0 **
2. Import package: import 'package:dio_smart_retry/dio_smart_retry.dart'

** For the old dio (ver. 4.+) use dio_smart_retry: ^1.4.0

Just add an interceptor to your dio:

final dio = Dio();
// Add the interceptor
dio.interceptors.add(RetryInterceptor(
  dio: dio,
  logPrint: print, // specify log function (optional)
  retries: 3, // retry count (optional)
  retryDelays: const [ // set delays between retries (optional)
    Duration(seconds: 1), // wait 1 sec before first retry
    Duration(seconds: 2), // wait 2 sec before second retry
    Duration(seconds: 3), // wait 3 sec before third retry
  ],
));

/// Sending a failing request for 3 times with 1s, then 2s, then 3s interval
await dio.get('https://mock.codes/500');

See example/dio_smart_retry_example.dart.

Responses with these http status codes will be retried by default:

• 408: RequestTimeout
• 429: TooManyRequests
• 500: InternalServerError
• 502: BadGateway
• 503: ServiceUnavailable
• 504: GatewayTimeout
• 440: LoginTimeout (IIS)
• 460: ClientClosedRequest (AWS Elastic Load Balancer)
• 499: ClientClosedRequest (ngnix)
• 520: WebServerReturnedUnknownError
• 521: WebServerIsDown
• 522: ConnectionTimedOut
• 523: OriginIsUnreachable
• 524: TimeoutOccurred
• 525: SSLHandshakeFailed
• 527: RailgunError
• 598: NetworkReadTimeoutError
• 599: NetworkConnectTimeoutError It's possible to override this list

It's possible to manually disable retry for a specified request. Use disableRetry extension for that:

final request = RequestOptions(path: '/')
  ..disableRetry = true;
await dio.fetch<String>(request);

or

final options = Options()
  ..disableRetry = true;
await dio.get<String>('/', options: options);

It's possible to add you own retryable status codes. Use retryableExtraStatuses parameter for that. Here is an example:

RetryInterceptor(
  dio: dio,
  retryableExtraStatuses: { status401Unauthorized },
)

or:

RetryInterceptor(
  dio: dio,
  retryableExtraStatuses: { 401 },
)

It's possible to override default retryable status codes list. Just make new instance of DefaultRetryEvaluator and pass your status codes there.
Here is an example:

final myStatuses = { status400BadRequest, status409Conflict };
dio.interceptors.add(
  RetryInterceptor(
    dio: dio,
    logPrint: print,
    retryEvaluator: DefaultRetryEvaluator(myStatuses).evaluate,
  ),
);

await dio.get<dynamic>('https://mock.codes/400');

Because dio's class for multipart data MultipartFile doesn't support stream rewinding (recreation) to support retry for multipart data you should use a class MultipartFileRecreatable instead of MultipartFile.
Here is an example:

final formData =
    FormData.fromMap({'file': MultipartFileRecreatable.fromFileSync('README.md')});
  await dio.post<dynamic>(
    'https://multipart.free.beeceptor.com/post500',
    data: formData,
  );

See the full example in the test: https://github.com/rodion-m/dio_smart_retry/blob/63a3bddae8b5a0581c35c4ae5e973996561d9100/test/multipart_retry_tests.dart#L32-L61