[Question]: Retry strategy sometimes works, sometimes returns on first try while writing unit tests about polly

[peter-csala]

You did not specify the ShouldHandle of the RetryStrategyOptions. The default value triggers only for OperationCanceledException. (doc)

[martincostello]

Just to "harden" the sample a bit, does the behaviour change or stay the same if you move the counter++; to be the first line of the lambda and change the catch to catch (ArgumentException)?

The would just rule out something else we can't see being thrown causing the test to fail and would also show that the lambda is definitely being called.

[tomatualus]

@martincostello Currently i am unable to reproduce the bug again, so i can't test out your suggestions

But i am 100% sure i did hit debug breakpoints both inside SomeAsyncStuff() and remember seeing ArgumentException as the one being thrown in the console output (before i wrapped it inside try/catch)

[tomatualus]

For additional information - This all started, when i was mocking redis database to throw a RedisTimeoutException, and observed it failing instantly, and not retrying. I tried many fixes, including adding [DebuggerStepThrough] attribute to the method and restarting the IDE. I guess the restart fixed it without me noticing.

Rider Version - 2023.2.3

[tomatualus]

And some SE post i have found with the same issue, but they were using VS and old polly version- https://stackoverflow.com/questions/44057939/exception-user-unhandled-reported-in-vs-debugger-when-using-polly/44079217#44079217

[tomatualus]

You did not specify the ShouldHandle of the RetryStrategyOptions. The default value triggers only for OperationCanceledException. (doc)

But doesn't that mean that any other exception than OperationCanceledException should keep the Retry strategy trying by default?

[peter-csala]

But doesn't that mean that any other exception than OperationCanceledException should keep the Retry strategy trying by default?

In case of Polly we can distinguish two types of exceptions from a strategy perspective: handled exceptions and not handled exceptions.

If the callback / to-be-decorated method throws a handled exception then retry will trigger if the attempt counter did not exceed the threshold. If it exceeded then it will throw the handled exception.

If the callback / to-be-decorated method throws a not handled exception then retry will not trigger just throws the not handled exception.

Old but gold documentation about this: https://github.com/App-vNext/Polly/wiki/Retry#how-polly-retry-works

[peter-csala]

@tomatualus Did we answer your question or do you need further clarification?

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[github-actions]

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