Memory issue when sharing CancelToken between posts for IO implementation

[kunstmusik]

Package

dio

Version

5.4.0

Operating-System

Android

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! Doctor found issues in 1 category.

Dart Version

3.1.3

Steps to Reproduce

1. Create a CancelToken
2. Make multiiple requests passing in the same CancelToken

Expected Result

No out of memory issues on Android.

Actual Result

Out of memory issues occur.

Dio's use of cancelFuture in dio/lib/src/adapters/io_adapter.dart differs from how it is used in browser_adapter.dart and exhibits different behavior. In IO, it captures on request in the callback to whenComplete in _fetch, which does not happen in the browser implementation.

This took us some time to discover as a memory leak issue. It would be great if this could be fixed, otherwise would love to see this documented so that future users will be aware of this issue.

[AlexV525]

Could you attach the minimal reproducible example and some analysis graphs or details?

[AlexV525]

@kuhnroyal I have been thinking about the cause of this issue for the last few days, it could be caused by referencing the resources of the request in callers like .whenComplete so they will only get released once the CancelToken canceled, but it doesn't, so memory leaks. Any ideas?

[AlexV525]

If yes, we might add a global map to cache the necessary instances for the corresponding cancel token.

[kuhnroyal]

I tried to enable the new leak tracking but didn't get very far yet...

[kunstmusik]

@AlexV525 I haven't had time to followup, but yes, as mentioned in my first message, we found that the .whenComplete callback captures over the Request:

      if (cancelFuture != null) {
        cancelFuture.whenComplete(() => request.abort());
      }

and whenComplete() also adds additional handlers each time it is called. So if a CancelToken is passed in to multiple fetches, it will keep accruing whenComplete handlers that all capture over individual requests.

[AlexV525]

@kunstmusik Can you verify if #2252 fixes the issue?