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Benchmark for strategy creation #1426

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Jul 24, 2023
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Benchmark for strategy creation #1426

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15 changes: 15 additions & 0 deletions ...tNet.Artifacts/results/Polly.Core.Benchmarks.CreationBenchmark-report-github.md
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```

BenchmarkDotNet v0.13.6, Windows 11 (10.0.22621.1992/22H2/2022Update/SunValley2) (Hyper-V)
Intel Xeon Platinum 8370C CPU 2.80GHz, 1 CPU, 16 logical and 8 physical cores
.NET SDK 7.0.306
[Host] : .NET 7.0.9 (7.0.923.32018), X64 RyuJIT AVX2

Job=MediumRun Toolchain=InProcessEmitToolchain IterationCount=15
LaunchCount=2 WarmupCount=10

```
| Method | Mean | Error | StdDev | Gen0 | Allocated |
|------------ |-----------:|---------:|---------:|-------:|----------:|
| Fallback_V7 | 114.8 ns | 1.84 ns | 2.70 ns | 0.0191 | 480 B |
| Fallback_V8 | 4,324.7 ns | 21.92 ns | 31.43 ns | 0.2518 | 6504 B |
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The creation in V8 is indeed more expensive as it involves a lot more infra. For this reason the recreation of strategies on hot path should be discouraged.

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What would your generic recommendation be?

In the sandbox app the fallback behaviour is trivial and could be cached, but in the code on which it was based there's dynamic per-invocation behaviour going on to select the fallback.

It feels that to support the same behaviour the more performant option would be to drop Polly fallbacks entirely and deal with it at the call site like any "normal" code, which if true doesn't feel great that the performance for this scenario has actually gone backwards.

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I don't think I have seen a scenario where you are "forced" to recreate a strategy on a hot path.

At worst you need to fallback to some dynamic value, but that can be archived by passing such value to the fallback action using ResilienceContext.

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In you code the caching could look like:

image

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Could you paste the code rather than a picture of it? 😄

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Sure, I tried to create a draft PR to your repo and got rejected.

public ResilienceStrategy<TResult> GetStrategy<TResult>(ApiEndpointOption endpoint, bool handleExecutionFaults, string resource)
{
    return _registry.GetOrAddStrategy<TResult>($"fallback/{resource}/{handleExecutionFaults}", builder =>
    {
        var shouldHandle = new PredicateBuilder<TResult>()
            .Handle<ApiException>()
            .HandleHttpRequestFault()
            .Handle<TaskCanceledException>();

        if (handleExecutionFaults)
        {
            shouldHandle = shouldHandle
                .Handle<BrokenCircuitException>()
                .Handle<IsolatedCircuitException>()
                .Handle<TimeoutRejectedException>();
        }

        builder
            .AddStrategy(GetStrategy(endpoint, resource))
            .AddFallback(new FallbackStrategyOptions<TResult>()
            {
                FallbackAction = context =>
                {
                    if (context.Context.Properties.TryGetValue(FallbackKeys<TResult>.FallbackValue, out var value) && value != null)
                    {
                        return Outcome.FromResultAsTask(value());
                    }

                    return Outcome.FromResultAsTask<TResult>(default);
                },
                ShouldHandle = shouldHandle,
                StrategyName = $"{endpoint.Name} Fallback",
            });
    });
}

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@martincostello martincostello Jul 24, 2023 •
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Do you have the code for FallbackKeys?

Nevermind, I can see it in the screenshot.

Comment on lines +14 to +15
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Wow that's a lot more 😅

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I think validation eats a lot of that as it involves reflection.

25 changes: 25 additions & 0 deletions bench/Polly.Core.Benchmarks/CreationBenchmark.cs
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namespace Polly.Core.Benchmarks;

#pragma warning disable CA1052 // Static holder types should be Static or NotInheritable

public class CreationBenchmark
{
[Benchmark]
public static void Fallback_V7()
{
Policy
.HandleResult<string>(s => true)
.FallbackAsync(_ => Task.FromResult("fallback"));
}

[Benchmark]
public static void Fallback_V8()
{
new ResilienceStrategyBuilder<string>()
.AddFallback(new()
{
FallbackAction = _ => Outcome.FromResultAsTask("fallback")
})
.Build();
}
}