Hedging now works without routing configuration

[martintmk]

Previously, the consumer was forced to configure the routing in order to use the hedging:

services
    .AddHttpClient("my-client")
    .AddStandardHedgingHandler()
    .RoutingStrategyBuilder.ConfigureOrderedGroups(options =>
    {
        options.Groups.Add(new EndpointGroup
        {
            Endpoints = new List<WeightedEndpoint>
            {
                new WeightedEndpoint
                {
                    Uri = new Uri("https://primary-url:1234"),
                }
            }
        });

        options.Groups.Add(new EndpointGroup
        {
            Endpoints = new List<WeightedEndpoint>
            {
                new WeightedEndpoint
                {
                    Uri = new Uri("https://secondary-url:1234"),
                }
            }
        });
    });

// ... 

var client = httpClientFactory.CreateClient("my-client");
var response = await client.GetAsync("https://primary-url:1234"); // or any URL, it will be replaced with the URLs above

Now, the consumer can just call AddStandardHedgingHandler and the hedging will work. The hedged requests will go to URL specified in the HttpRequestMessage.

services
    .AddHttpClient("my-client")
    .AddStandardHedgingHandler();

// ... 

var client = httpClientFactory.CreateClient("my-client");
var response = await client.GetAsync("https://primary-url:1234");

I have also added a new benchmark for these changes and some perf improvements:

Before:

Method	Type	Mean	Error	StdDev	Gen0	Allocated
HedgingCall	Weighted	7.560 us	0.1658 us	0.2430 us	0.0458	1272 B
HedgingCall	Ordered	7.101 us	0.0297 us	0.0436 us	0.0458	1272 B
HedgingCall	Weighted, ManyRoutes	7.649 us	0.0405 us	0.0593 us	0.0458	1272 B
HedgingCall	Ordered, ManyRoutes	7.222 us	0.1072 us	0.1605 us	0.0458	1272 B
HedgingCall	NoRoutes	5.881 us	0.0217 us	0.0305 us	0.0305	832 B

After:

Method	Type	Mean	Error	StdDev	Gen0	Allocated
HedgingCall	Weighted	6.908 us	0.0673 us	0.1007 us	0.0381	1052 B
HedgingCall	Ordered	6.779 us	0.0632 us	0.0926 us	0.0381	1052 B
HedgingCall	Weighted, ManyRoutes	7.322 us	0.0221 us	0.0309 us	0.0381	1053 B
HedgingCall	Ordered, ManyRoutes	6.755 us	0.0604 us	0.0885 us	0.0381	1052 B
HedgingCall	NoRoutes	5.866 us	0.0194 us	0.0272 us	0.0305	832 B

I have also updated the HttpResilience benchmarks:

Method	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Allocated	Alloc Ratio
DefaultClient	329.3 ns	3.99 ns	5.85 ns	1.00	0.00	0.0234	592 B	1.00
SingleHandler	338.3 ns	4.89 ns	6.85 ns	1.03	0.03	0.0262	664 B	1.12
StandardResilienceHandler	2,972.9 ns	21.21 ns	31.10 ns	9.03	0.16	0.0267	752 B	1.27
StandardHedgingHandler_RoutesFromRequest	6,032.5 ns	36.62 ns	52.52 ns	18.31	0.30	0.0305	832 B	1.41
StandardHedgingHandler_RoutesFromConfig	6,925.1 ns	36.73 ns	54.97 ns	21.04	0.39	0.0381	1063 B	1.80

Microsoft Reviewers: Open in CodeFlow

[RussKie]

👍 though I'm not an SME in this.

[RussKie]

[nit]

Suggested change

	if (_provider == null)
	if (_provider is null)

[rafal-mz]

Do we need to await?

[martintmk]

Yes, as we need to dispose the RequestRoutingStrategy after callback is executed.