[GitHub] [flink] XComp commented on pull request #18963: [FLINK-26450][fs] Adds error handling to FileStateHandle.discardState

[GitBox <gi...@apache.org>]

XComp commented on pull request #18963:
URL: https://github.com/apache/flink/pull/18963#issuecomment-1057926590


   Thanks for your concerns. I agree that it's a bit of overkill for this specific usecase. See my inline comments below:
   > 1. TestingFileSystem might be brittle because it has a lot of unsupported operations. Can't we delegate everything except delete to some "real" FS?
   The initial intention of `TestingFileSystem` was to have a "framework" to test against in the future. Having all the method throw `UnsupportedOperationException` if not specified forces the developer writing a test to define exactly what behavior to expect from the `FileSystem`. For default behavior, having a temporary filesystem would be good enough.
   
   > 2. Callbacks make it less readdable, and mutable callbacks - error-prone, why do we need to reset them?
   The idea of resetting them to make each test define the exact context it's running in. Where do you see that it's error-prone? That just would indicate that the test's isn't defined precisely.
   Ideally, we would have a `FileSystem` being specified through a `Builder` pattern and created per test. But the lifecycle of the `FileSystem` should happen outside (i.e. around) the test to make sure that it's get removed again, afterwards. This prevents us from initializing the `FileSystem` within the test. Therefore, I tried this approach with mutable callbacks.
   
   > 3. I'm wondering whether a local FS can be picked up instead of a testing FS for some reason - should we guard against it using some "test://" scheme?
   I don't understand this proposal. Do you see a way to simulate an error using the local FS? I couldn't come up with a solution here.


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