Elaborate about synchronous vs asynchronous executions

[martintmk]

Details on the issue fix or feature implementation

Elaborating on our async vs sync model in V8.

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[martincostello]

Suggested change

Polly's core, from version 8, fundamentally focuses on asynchronous executions. However, it also supports synchronous executions, which require minimal effort for authors developing custom resilience strategies. This support is enabled by passing and wrapping the synchronous callback provided by the user into an asynchronous one, which returns a completed value task upon completion. This feature allows custom resilience strategies to treat all executions as asynchronous. In cases of synchronous executions, the function simply returns completed tasks upon awaiting.

Polly's core, from version 8, fundamentally focuses on asynchronous executions. However, it also supports synchronous executions, which require minimal effort for authors developing custom resilience strategies. This support is enabled by passing and wrapping the synchronous callback provided by the user into an asynchronous one, which returns a completed `ValueTask` upon completion. This feature allows custom resilience strategies to treat all executions as asynchronous. In cases of synchronous execution, the method simply returns a completed task upon awaiting.

[martincostello]

Suggested change

A common scenario that illustrates this is the circuit breaker, which allows hundreds of concurrent executions. In failure scenarios, only one will trigger the opening of the circuit. If this single execution was synchronous, it would involve some synchronous-over-asynchronous code. This situation occurs because, in the circuit breaker, we wanted to avoid duplicating code for synchronous executions. However, this does not impact the scalability of the Circuit Breaker, since such events are rare and do not execute on the hot path.

A common scenario that illustrates this is the circuit breaker, which allows for hundreds of concurrent executions. In failure scenarios, only one will trigger the opening of the circuit. If this single execution was synchronous, it would involve some synchronous-over-asynchronous code. This situation occurs because, in the circuit breaker, we wanted to avoid duplicating code for synchronous executions. However, this does not impact the scalability of the Circuit Breaker, since such events are rare and do not execute on the hot path.

[codecov]

Codecov Report

Merging #1456 (55c3021) into main (0f38c51) will not change coverage.
Report is 2 commits behind head on main.
The diff coverage is n/a.

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