Introduce RetryResilienceStrategy

src/Polly.Core.Tests/Retry/RetryConstantsTests.cs

@@ -0,0 +1,18 @@
+using Polly.Retry;
+
+namespace Polly.Core.Tests.Retry;
+
+public class RetryConstantsTests
+{
+    [Fact]
+    public void EnsureDefaults()
+    {
+        RetryConstants.DefaultBackoffType.Should().Be(RetryBackoffType.Exponential);
+        RetryConstants.DefaultBaseDelay.Should().Be(TimeSpan.FromSeconds(2));
+        RetryConstants.DefaultRetryCount.Should().Be(3);
+        RetryConstants.MaxRetryCount.Should().Be(100);
+        RetryConstants.InfiniteRetryCount.Should().Be(-1);
+        RetryConstants.StrategyType.Should().Be("Retry");
+        RetryConstants.OnRetryEvent.Should().Be("OnRetry");
+    }
+}

src/Polly.Core.Tests/Retry/RetryDelayArgumentsTests.cs

@@ -7,9 +7,10 @@ public class RetryDelayArgumentsTests
     [Fact]
     public void Ctor_Ok()
     {
-        var args = new RetryDelayArguments(ResilienceContext.Get(), 2);
+        var args = new RetryDelayArguments(ResilienceContext.Get(), 2, TimeSpan.FromSeconds(2));
 
         args.Context.Should().NotBeNull();
         args.Attempt.Should().Be(2);
+        args.DelayHint.Should().Be(TimeSpan.FromSeconds(2));
     }
 }

src/Polly.Core.Tests/Retry/RetryDelayGeneratorTests.cs

@@ -14,7 +14,7 @@ public async Task NoGeneratorRegisteredForType_EnsureDefaultValue()
         var result = await new RetryDelayGenerator()
             .SetGenerator<int>((_, _) => TimeSpan.Zero)
             .CreateHandler()!
-            .Generate(new Outcome<bool>(true), new RetryDelayArguments(ResilienceContext.Get(), 0));
+            .Generate(new Outcome<bool>(true), new RetryDelayArguments(ResilienceContext.Get(), 0, TimeSpan.FromSeconds(2)));
 
         result.Should().Be(TimeSpan.MinValue);
     }
@@ -28,7 +28,7 @@ public async Task GeneratorRegistered_EnsureValueNotIgnored(TimeSpan delay)
         var result = await new RetryDelayGenerator()
             .SetGenerator<int>((_, _) => delay)
             .CreateHandler()!
-            .Generate(new Outcome<int>(0), new RetryDelayArguments(ResilienceContext.Get(), 0));
+            .Generate(new Outcome<int>(0), new RetryDelayArguments(ResilienceContext.Get(), 0, TimeSpan.FromSeconds(2)));
 
         result.Should().Be(delay);
     }

src/Polly.Core.Tests/Retry/RetryHelperTests.cs

@@ -0,0 +1,61 @@
+using System;
+using Polly.Retry;
+
+namespace Polly.Core.Tests.Retry;
+
+public class RetryHelperTests
+{
+    [Fact]
+    public void IsValidDelay_Ok()
+    {
+        RetryHelper.IsValidDelay(TimeSpan.Zero).Should().BeTrue();
+        RetryHelper.IsValidDelay(TimeSpan.FromSeconds(1)).Should().BeTrue();
+        RetryHelper.IsValidDelay(TimeSpan.MaxValue).Should().BeTrue();
+        RetryHelper.IsValidDelay(TimeSpan.MinValue).Should().BeFalse();
+        RetryHelper.IsValidDelay(TimeSpan.FromMilliseconds(-1)).Should().BeFalse();
+    }
+
+    [Fact]
+    public void UnsupportedRetryBackoffType_Throws()
+    {
+        RetryBackoffType type = (RetryBackoffType)99;
+
+        Assert.Throws<ArgumentOutOfRangeException>(() => RetryHelper.GetRetryDelay(type, 0, TimeSpan.FromSeconds(1)));
+    }
+
+    [Fact]
+    public void Constant_Ok()
+    {
+        RetryHelper.GetRetryDelay(RetryBackoffType.Constant, 0, TimeSpan.Zero).Should().Be(TimeSpan.Zero);
+        RetryHelper.GetRetryDelay(RetryBackoffType.Constant, 1, TimeSpan.Zero).Should().Be(TimeSpan.Zero);
+        RetryHelper.GetRetryDelay(RetryBackoffType.Constant, 2, TimeSpan.Zero).Should().Be(TimeSpan.Zero);
+
+        RetryHelper.GetRetryDelay(RetryBackoffType.Constant, 0, TimeSpan.FromSeconds(1)).Should().Be(TimeSpan.FromSeconds(1));
+        RetryHelper.GetRetryDelay(RetryBackoffType.Constant, 1, TimeSpan.FromSeconds(1)).Should().Be(TimeSpan.FromSeconds(1));
+        RetryHelper.GetRetryDelay(RetryBackoffType.Constant, 2, TimeSpan.FromSeconds(1)).Should().Be(TimeSpan.FromSeconds(1));
+    }
+
+    [Fact]
+    public void Linear_Ok()
+    {
+        RetryHelper.GetRetryDelay(RetryBackoffType.Linear, 0, TimeSpan.Zero).Should().Be(TimeSpan.Zero);
+        RetryHelper.GetRetryDelay(RetryBackoffType.Linear, 1, TimeSpan.Zero).Should().Be(TimeSpan.Zero);
+        RetryHelper.GetRetryDelay(RetryBackoffType.Linear, 2, TimeSpan.Zero).Should().Be(TimeSpan.Zero);
+
+        RetryHelper.GetRetryDelay(RetryBackoffType.Linear, 0, TimeSpan.FromSeconds(1)).Should().Be(TimeSpan.FromSeconds(1));
+        RetryHelper.GetRetryDelay(RetryBackoffType.Linear, 1, TimeSpan.FromSeconds(1)).Should().Be(TimeSpan.FromSeconds(2));
+        RetryHelper.GetRetryDelay(RetryBackoffType.Linear, 2, TimeSpan.FromSeconds(1)).Should().Be(TimeSpan.FromSeconds(3));
+    }
+
+    [Fact]
+    public void Exponential_Ok()
+    {
+        RetryHelper.GetRetryDelay(RetryBackoffType.Exponential, 0, TimeSpan.Zero).Should().Be(TimeSpan.Zero);
+        RetryHelper.GetRetryDelay(RetryBackoffType.Exponential, 1, TimeSpan.Zero).Should().Be(TimeSpan.Zero);
+        RetryHelper.GetRetryDelay(RetryBackoffType.Exponential, 2, TimeSpan.Zero).Should().Be(TimeSpan.Zero);
+
+        RetryHelper.GetRetryDelay(RetryBackoffType.Exponential, 0, TimeSpan.FromSeconds(1)).Should().Be(TimeSpan.FromSeconds(1));
+        RetryHelper.GetRetryDelay(RetryBackoffType.Exponential, 1, TimeSpan.FromSeconds(1)).Should().Be(TimeSpan.FromSeconds(2));
+        RetryHelper.GetRetryDelay(RetryBackoffType.Exponential, 2, TimeSpan.FromSeconds(1)).Should().Be(TimeSpan.FromSeconds(4));
+    }
+}

src/Polly.Core.Tests/Retry/RetryResilienceStrategyBuilderExtensionsTests.cs

@@ -0,0 +1,70 @@
+using System.ComponentModel.DataAnnotations;
+using Polly.Builder;
+using Polly.Retry;
+using Xunit;
+
+namespace Polly.Core.Tests.Retry;
+
+public class RetryResilienceStrategyBuilderExtensionsTests
+{
+    public static readonly TheoryData<Action<ResilienceStrategyBuilder>> OverloadsData = new()
+    {
+        builder =>
+        {
+            builder.AddRetry(retry=>retry.Result(10));
+            AssertStrategy(builder, RetryBackoffType.Exponential, 3, TimeSpan.FromSeconds(2));
+        },
+        builder =>
+        {
+            builder.AddRetry(retry=>retry.Result(10), RetryBackoffType.Linear);
+            AssertStrategy(builder, RetryBackoffType.Linear, 3, TimeSpan.FromSeconds(2));
+        },
+        builder =>
+        {
+            builder.AddRetry(retry=>retry.Result(10), RetryBackoffType.Linear, 2, TimeSpan.FromSeconds(1));
+            AssertStrategy(builder, RetryBackoffType.Linear, 2, TimeSpan.FromSeconds(1));
+        },
+    };
+
+    [MemberData(nameof(OverloadsData))]
+    [Theory]
+    public void AddRetry_Overloads_Ok(Action<ResilienceStrategyBuilder> configure)
+    {
+        var builder = new ResilienceStrategyBuilder();
+        var options = new RetryStrategyOptions();
+
+        builder.Invoking(b => configure(b)).Should().NotThrow();
+    }
+
+    [Fact]
+    public void AddRetry_DefaultOptions_Ok()
+    {
+        var builder = new ResilienceStrategyBuilder();
+        var options = new RetryStrategyOptions();
+
+        builder.AddRetry(options);
+
+        AssertStrategy(builder, options.BackoffType, options.RetryCount, options.BaseDelay);
+    }
+
+    private static void AssertStrategy(ResilienceStrategyBuilder builder, RetryBackoffType type, int retries, TimeSpan delay)
+    {
+        var strategy = (RetryResilienceStrategy)builder.Build();
+
+        strategy.BackoffType.Should().Be(type);
+        strategy.RetryCount.Should().Be(retries);
+        strategy.BaseDelay.Should().Be(delay);
+    }
+
+    [Fact]
+    public void AddRetry_InvalidOptions_Throws()
+    {
+        var builder = new ResilienceStrategyBuilder();
+
+        builder
+            .Invoking(b => b.AddRetry(new RetryStrategyOptions { ShouldRetry = null! }))
+            .Should()
+            .Throw<ValidationException>()
+            .WithMessage("The retry strategy options are invalid.*");
+    }
+}

src/Polly.Core.Tests/Retry/RetryResilienceStrategyTests.cs

@@ -0,0 +1,176 @@
+using Moq;
+using Polly.Retry;
+using Polly.Telemetry;
+
+namespace Polly.Core.Tests.Retry;
+
+public class RetryResilienceStrategyTests
+{
+    private readonly RetryStrategyOptions _options = new();
+    private readonly FakeTimeProvider _timeProvider = new();
+    private readonly Mock<ResilienceTelemetry> _telemetry = new();
+
+    [Fact]
+    public void ShouldRetryEmpty_Skipped()
+    {
+        bool called = false;
+        _options.OnRetry.Add<int>(() => called = true);
+        SetupNoDelay();
+        var sut = CreateSut();
+
+        sut.Execute(_ => 0, default);
+
+        called.Should().BeFalse();
+    }
+
+    [Fact]
+    public void Retry_RetryCount_Respected()
+    {
+        int calls = 0;
+        _options.OnRetry.Add<int>(() => calls++);
+        _options.ShouldRetry.Result<int>(0);
+        _options.RetryCount = 12;
+        SetupNoDelay();
+        var sut = CreateSut();
+
+        sut.Execute(_ => 0, default);
+
+        calls.Should().Be(12);
+    }
+
+    [Fact]
+    public void RetryException_RetryCount_Respected()
+    {
+        int calls = 0;
+        _options.OnRetry.Add<int>((args, _) =>
+        {
+            args.Exception.Should().BeOfType<InvalidOperationException>();
+            calls++;
+        });
+        _options.ShouldRetry.Exception<InvalidOperationException>();
+        _options.RetryCount = 3;
+        SetupNoDelay();
+        var sut = CreateSut();
+
+        Assert.Throws<InvalidOperationException>(() => sut.Execute<int>(_ => throw new InvalidOperationException(), default));
+
+        calls.Should().Be(3);
+    }
+
+    [Fact]
+    public void Retry_Infinite_Respected()
+    {
+        int calls = 0;
+        _options.BackoffType = RetryBackoffType.Constant;
+        _options.OnRetry.Add<int>((_, args) =>
+        {
+            if (args.Attempt > RetryConstants.MaxRetryCount)
+            {
+                throw new InvalidOperationException();
+            }
+
+            calls++;
+        });
+        _options.ShouldRetry.Result(0);
+        _options.RetryCount = RetryStrategyOptions.InfiniteRetryCount;
+        SetupNoDelay();
+        var sut = CreateSut();
+
+        Assert.Throws<InvalidOperationException>(() => sut.Execute(_ => 0, default));
+
+        calls.Should().Be(RetryConstants.MaxRetryCount + 1);
+    }
+
+    [Fact]
+    public void RetryDelayGenerator_Respected()
+    {
+        int calls = 0;
+        _options.OnRetry.Add<int>(() => calls++);
+        _options.ShouldRetry.Result<int>(0);
+        _options.RetryCount = 3;
+        _options.BackoffType = RetryBackoffType.Constant;
+        _options.RetryDelayGenerator.SetGenerator<int>((_, _) => TimeSpan.FromMilliseconds(123));
+        _timeProvider.SetupDelay(TimeSpan.FromMilliseconds(123));
+
+        var sut = CreateSut();
+
+        sut.Execute(_ => 0, default);
+
+        _timeProvider.Verify(v => v.Delay(TimeSpan.FromMilliseconds(123), default), Times.Exactly(3));
+    }
+
+    [Fact]
+    public void OnRetry_EnsureCorrectArguments()
+    {
+        var attempts = new List<int>();
+        var delays = new List<TimeSpan>();
+        _options.OnRetry.Add<int>((outcome, args) =>
+        {
+            attempts.Add(args.Attempt);
+            delays.Add(args.RetryDelay);
+
+            outcome.Exception.Should().BeNull();
+            outcome.Result.Should().Be(0);
+        });
+
+        _options.ShouldRetry.Result<int>(0);
+        _options.RetryCount = 3;
+        _options.BackoffType = RetryBackoffType.Linear;
+        _timeProvider.SetupAnyDelay();
+
+        var sut = CreateSut();
+
+        sut.Execute(_ => 0, default);
+
+        attempts.Should().HaveCount(3);
+        attempts[0].Should().Be(0);
+        attempts[1].Should().Be(1);
+        attempts[2].Should().Be(2);
+
+        delays[0].Should().Be(TimeSpan.FromSeconds(2));
+        delays[1].Should().Be(TimeSpan.FromSeconds(4));
+        delays[2].Should().Be(TimeSpan.FromSeconds(6));
+    }
+
+    [Fact]
+    public void RetryDelayGenerator_EnsureCorrectArguments()
+    {
+        var attempts = new List<int>();
+        var hints = new List<TimeSpan>();
+        _options.RetryDelayGenerator.SetGenerator<int>((outcome, args) =>
+        {
+            attempts.Add(args.Attempt);
+            hints.Add(args.DelayHint);
+
+            outcome.Exception.Should().BeNull();
+            outcome.Result.Should().Be(0);
+
+            return TimeSpan.Zero;
+        });
+
+        _options.ShouldRetry.Result<int>(0);
+        _options.RetryCount = 3;
+        _options.BackoffType = RetryBackoffType.Linear;
+        _timeProvider.SetupAnyDelay();
+
+        var sut = CreateSut();
+
+        sut.Execute(_ => 0, default);
+
+        attempts.Should().HaveCount(3);
+        attempts[0].Should().Be(0);
+        attempts[1].Should().Be(1);
+        attempts[2].Should().Be(2);
+
+        hints[0].Should().Be(TimeSpan.FromSeconds(2));
+        hints[1].Should().Be(TimeSpan.FromSeconds(4));
+        hints[2].Should().Be(TimeSpan.FromSeconds(6));
+    }
+
+    private void SetupNoDelay() => _options.RetryDelayGenerator.SetGenerator<int>((_, _) => TimeSpan.Zero);
+
+    private RetryResilienceStrategy CreateSut()
+    {
+        return new RetryResilienceStrategy(_options, _timeProvider.Object, _telemetry.Object);
+    }
+}