Proper way to handle multiple services with polly circuit breaker

Question

I have an application where we communicate with hundreds of HTTPs endpoints. The application is a proxy of sorts.

When testing with polly, I've noticed that if one endpoint, say api.endpoint1.com fails, the calls to api.endpoint2.com and api.endpoint3.com will also be in an open/blocked state.

This makes sense as I've only defined one policy, but what is the recommended approach to handling this scenario so that calls to unrelated endpoints are not blocked due to another having performance issues?

Do I create a collection of Policy's, one for each endpoint or is there a way to supply a context key of sorts(i.e. the hostname) to scope the failures to a given host endpoint?

I've reviewed Polly's docs regarding context keys and it appears these are a way to exchange data back and forth and not what I'm looking for here.

var policy = Policy
            .Handle<TimeoutException>()
            .CircuitBreaker(1, TimeSpan.FromSeconds(1));
                
//dynamic, large list of endpoints. 
var m = new HttpRequestMessage(HttpMethod.Post, "https://api.endpoint1.com")
{
    Content = new StringContent("some JSON data here", Encoding.UTF8,"application/json")
};


policy.Execute(() => HTTPClientWrapper.PostAsync(message));

Answer 1

Yes, your best bet is to create a separate policy per endpoint. This is better than doing it per host because an endpoint may be slow responding for a reason that's specific to that endpoint (e.g., stored procedure is slow).

I've used a Dictionary<string, Policy> with the endpoint URL as the key.

if (!_circuitBreakerPolices.ContainsKey(url))
{
    CircuitBreakerPolicy policy = Policy.Handle<Exception>().AdvancedCircuitBreakerAsync(
        onBreak: ...
    );
    _circuitBreakerPolicies.Add(url, policy);
}
await _circuitBreakerPolicies[url].ExecuteAsync(async () => ... );