[Feature request]: Enumerate policies in ResiliencePipelineRegistry about polly

[martintmk]

Hey @IGx89

In Polly V8 there is no way to retrieve the circuit breaker state from an instance of ResiliencePipeline. Even if enumerating pipeline from registry was available it wouldn't help.

What you want to do is to keep registry of CircuitBreakerStateProvider as you are creating the pipelines. See this test that demonstrates your use-case:

// Arrange
var states = new ConcurrentBag<CircuitBreakerStateProvider>();
using var registry = new ResiliencePipelineRegistry<string>();

// Act
_ = registry.GetOrAddPipeline("A", builder =>
{
    var stateProvider = new CircuitBreakerStateProvider();
    builder.AddCircuitBreaker(new() { StateProvider = stateProvider });
    states.Add(stateProvider);
});

_ = registry.GetOrAddPipeline("B", builder =>
{
    var stateProvider = new CircuitBreakerStateProvider();
    builder.AddCircuitBreaker(new() { StateProvider = stateProvider });
    states.Add(stateProvider);
});

_ = registry.TryAddBuilder("C", (builder, _) =>
{
    var stateProvider = new CircuitBreakerStateProvider();
    builder.AddCircuitBreaker(new() { StateProvider = stateProvider });
    states.Add(stateProvider);
});

// Assert
states.Should().HaveCount(2);
registry.GetPipeline("C");
states.Should().HaveCount(3);

foreach (var state in states)
{
    state.CircuitState.Should().Be(CircuitState.Closed);
}

doesn't implement IEnumerable nor provides any way to get a list of the pipelines. Was that removed deliberately? If not, could that functionality be added back?

This was deliberate choice due to dynamic nature of registry. The pipelines are not explicitly added, instead these are created on demand when requested. Additionally, with the minimal nature of ResiliencePipeline there is now way to retrieve any information about strategies from it.

Also created a PR that adds this test: #1829

[IGx89]

Thanks a lot for the detailed explanation and code example! That's very helpful. I definitely have a lot more learning to do it looks :)