Merge pull request #393 from reisenberger/v570tidyTtlStrategies

More on `ResultTtl`, merged to `v5.7.0` branch

CHANGELOG.md

@@ -1,6 +1,7 @@
 
 ## 5.7.0
 - Minor cache fixes
+- Add ability to calculate cache Ttl based on item to cache
 - Allow user-created custom policies 
 
 ## 5.6.1

README.md

@@ -947,6 +947,7 @@ For details of changes by release see the [change log](https://github.com/App-vN
 * [@reisenberger](https://github.com/reisenberger) - Add new .HandleInner<TException>(...) syntax for handling inner exceptions natively.
 * [@rjongeneelen](https://github.com/rjongeneelen) and [@reisenberger](https://github.com/reisenberger) - Allow PolicyWrap configuration to configure policies via interfaces. 
 * [@reisenberger](https://github.com/reisenberger) - Performance improvements.
+* [@awarrenlove](https://github.com/awarrenlove) - Add ability to calculate cache Ttl based on item to cache.
 
 # Sample Projects
 

src/Polly.Net40Async.nuspec

@@ -18,6 +18,7 @@
      5.7.0
      ---------------------
      - Minor cache fixes
+     - Add ability to calculate cache Ttl based on item to cache
      - Allow user-created custom policies
 
      5.6.1

src/Polly.Shared/Caching/ResultTtl.cs

@@ -5,22 +5,30 @@
 namespace Polly.Caching
 {
     /// <summary>
-    /// Defines a ttl strategy which will cache items with some calculation from the result of the execution.
+    /// Defines a ttl strategy which can calculate a duration to cache items dynamically based on the execution context and result of the execution.
     /// </summary>
-
+    /// <typeparam name="TResult">The type of results that the ttl calculation function will take as an input parameter.</typeparam>
     public class ResultTtl<TResult> : ITtlStrategy<TResult>
     {
-        private readonly Func<TResult, Ttl> ttlFunc;
+        private readonly Func<Context, TResult, Ttl> _ttlFunc;
 
         /// <summary>
-        /// Constructs a new instance of the <see cref="ResultTtl{TResult}"/> ttl strategy.
+        /// Constructs a new instance of the <see cref="ResultTtl{TResult}"/> ttl strategy, with a func calculating <see cref="Ttl"/> based on the <typeparamref name="TResult"/> value to cache.
         /// </summary>
         /// <param name="ttlFunc">The function to calculate the TTL for which cache items should be considered valid.</param>
         public ResultTtl(Func<TResult, Ttl> ttlFunc)
         {
             if (ttlFunc == null) throw new ArgumentNullException(nameof(ttlFunc));
+            _ttlFunc = (context, result) => ttlFunc(result);
+        }
 
-            this.ttlFunc = ttlFunc;
+        /// <summary>
+        /// Constructs a new instance of the <see cref="ResultTtl{TResult}"/> ttl strategy, with a func calculating <see cref="Ttl"/> based on the execution <see cref="Context"/> and <typeparamref name="TResult"/> value to cache.
+        /// </summary>
+        /// <param name="ttlFunc">The function to calculate the TTL for which cache items should be considered valid.</param>
+        public ResultTtl(Func<Context, TResult, Ttl> ttlFunc)
+        {
+            _ttlFunc = ttlFunc ?? throw new ArgumentNullException(nameof(ttlFunc));
         }
 
         /// <summary>
@@ -32,7 +40,7 @@ public ResultTtl(Func<TResult, Ttl> ttlFunc)
 
         public Ttl GetTtl(Context context, TResult result)
         {
-            return ttlFunc(result);
+            return _ttlFunc(context, result);
         }
     }
 }

src/Polly.SharedSpecs/Caching/ResultTtlSpecs.cs

@@ -1,8 +1,7 @@
 using System;
-using System.Collections.Generic;
-using System.Text;
 using FluentAssertions;
 using Polly.Caching;
+using Polly.Specs.Helpers.Caching;
 using Xunit;
 
 namespace Polly.Specs.Caching
@@ -12,15 +11,31 @@ public class ResultTtlSpecs
         [Fact]
         public void Should_throw_when_func_is_null()
         {
-            Action configure = () => new ResultTtl<dynamic>(null);
+            Action configure = () => new ResultTtl<object>((Func<object, Ttl>)null);
+
+            configure.ShouldThrow<ArgumentNullException>().And.ParamName.Should().Be("ttlFunc");
+        }
+
+        [Fact]
+        public void Should_throw_when_func_is_null_using_context()
+        {
+            Action configure = () => new ResultTtl<object>((Func<Context, object, Ttl>)null);
 
             configure.ShouldThrow<ArgumentNullException>().And.ParamName.Should().Be("ttlFunc");
         }
 
         [Fact]
         public void Should_not_throw_when_func_is_set()
         {
-            Action configure = () => new ResultTtl<dynamic>((result) => new Ttl());
+            Action configure = () => new ResultTtl<object>((result) => new Ttl());
+
+            configure.ShouldNotThrow();
+        }
+
+        [Fact]
+        public void Should_not_throw_when_func_is_set_using_context()
+        {
+            Action configure = () => new ResultTtl<object>((context, result) => new Ttl());
 
             configure.ShouldNotThrow();
         }
@@ -29,13 +44,27 @@ public void Should_not_throw_when_func_is_set()
         public void Should_return_func_result()
         {
             TimeSpan ttl = TimeSpan.FromMinutes(1);
-            Func<dynamic, Ttl> func = (result) => { return new Ttl(ttl); };
+            Func<dynamic, Ttl> func = (result) => { return new Ttl(result.Ttl); };
 
             ResultTtl<dynamic> ttlStrategy = new ResultTtl<dynamic>(func);
 
             Ttl retrieved = ttlStrategy.GetTtl(new Context("someExecutionKey"), new { Ttl = ttl });
-            retrieved.Timespan.Should().BeCloseTo(ttl);
+            retrieved.Timespan.Should().Be(ttl);
             retrieved.SlidingExpiration.Should().BeFalse();
         }
+
+        [Fact]
+        public void Should_return_func_result_using_context()
+        {
+            const string specialKey = "specialKey";
+
+            TimeSpan ttl = TimeSpan.FromMinutes(1);
+            Func<Context, dynamic, Ttl> func = (context, result) => { return context.ExecutionKey == specialKey ? new Ttl(TimeSpan.Zero) : new Ttl(result.Ttl); };
+
+            ResultTtl<dynamic> ttlStrategy = new ResultTtl<dynamic>(func);
+
+            ttlStrategy.GetTtl(new Context("someExecutionKey"), new { Ttl = ttl }).Timespan.Should().Be(ttl);
+            ttlStrategy.GetTtl(new Context(specialKey), new { Ttl = ttl }).Timespan.Should().Be(TimeSpan.Zero);
+        }
     }
 }

src/Polly.nuspec

@@ -18,6 +18,7 @@
      5.7.0
      ---------------------
      - Minor cache fixes
+     - Add ability to calculate cache Ttl based on item to cache
      - Allow user-created custom policies
 
      5.6.1