Honor cache control directives for timestamp cache

readme.md

@@ -54,16 +54,19 @@ Frequency of updates to data is relatively low compared to reads
 ```mermaid
 graph TD
     Request
+    NoCache{Has no-cache<br/>in Cache-Control?}
     HasMaxAge{Has max-age<br/>or max-stale<br/>in Cache-Control?}
-    CacheValid{Cached timestamp<br/>within allowed<br/>staleness?}
+    CacheValid{Cached timestamp<br/>within allowed<br/>staleness?<br/>Considers min-fresh}
     FreshTimestamp[Get fresh timestamp<br/>from SQL]
     UseCached[Use cached timestamp]
     CalculateEtag[Calculate current ETag<br/>based on timestamp<br/>from web assembly and SQL]
     IfNoneMatch{Has<br/>If-None-Match<br/>header?}
     EtagMatch{Current<br/>Etag matches<br/>If-None-Match?}
     AddETag[Add current ETag<br/>to Response headers]
     304[Respond with<br/>304 Not-Modified]
-    Request --> HasMaxAge
+    Request --> NoCache
+    NoCache -->|Yes| FreshTimestamp
+    NoCache -->|No| HasMaxAge
     HasMaxAge -->|Yes| CacheValid
     HasMaxAge -->|No| FreshTimestamp
     CacheValid -->|Yes| UseCached
@@ -145,7 +148,7 @@ internal static string BuildEtag(string timeStamp, string? suffix)
     return $"\"{AssemblyWriteTime}-{timeStamp}-{suffix}\"";
 }
 ```
-<sup><a href='/src/Delta/DeltaExtensions_Shared.cs#L285-L297' title='Snippet source file'>snippet source</a> | <a href='#snippet-BuildEtag' title='Start of snippet'>anchor</a></sup>
+<sup><a href='/src/Delta/DeltaExtensions_Shared.cs#L326-L338' title='Snippet source file'>snippet source</a> | <a href='#snippet-BuildEtag' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 

readme.source.md

@@ -33,16 +33,19 @@ Frequency of updates to data is relatively low compared to reads
 ```mermaid
 graph TD
     Request
+    NoCache{Has no-cache<br/>in Cache-Control?}
     HasMaxAge{Has max-age<br/>or max-stale<br/>in Cache-Control?}
-    CacheValid{Cached timestamp<br/>within allowed<br/>staleness?}
+    CacheValid{Cached timestamp<br/>within allowed<br/>staleness?<br/>Considers min-fresh}
     FreshTimestamp[Get fresh timestamp<br/>from SQL]
     UseCached[Use cached timestamp]
     CalculateEtag[Calculate current ETag<br/>based on timestamp<br/>from web assembly and SQL]
     IfNoneMatch{Has<br/>If-None-Match<br/>header?}
     EtagMatch{Current<br/>Etag matches<br/>If-None-Match?}
     AddETag[Add current ETag<br/>to Response headers]
     304[Respond with<br/>304 Not-Modified]
-    Request --> HasMaxAge
+    Request --> NoCache
+    NoCache -->|Yes| FreshTimestamp
+    NoCache -->|No| HasMaxAge
     HasMaxAge -->|Yes| CacheValid
     HasMaxAge -->|No| FreshTimestamp
     CacheValid -->|Yes| UseCached

src/Delta/DeltaExtensions_Shared.cs

@@ -169,24 +169,36 @@ sealed record TimeStampCache(string Value, long Ticks);
     static bool TryGetCachedTimeStamp(HttpRequest request, [NotNullWhen(true)] out string? timeStamp)
     {
         timeStamp = null;
+        var cacheControl = request.Headers.CacheControl;
+
+        if (HasDirective(cacheControl, "no-cache"))
+        {
+            return false;
+        }
+
         var cache = timeStampCache;
         if (cache is null)
         {
             return false;
         }
 
-        if (!TryParseStaleness(request.Headers.CacheControl, out var maxSeconds))
+        if (!TryParseStaleness(cacheControl, out var maxSeconds))
         {
             return false;
         }
 
-        if (maxSeconds != int.MaxValue)
+        var elapsed = Stopwatch.GetElapsedTime(cache.Ticks);
+
+        if (maxSeconds != int.MaxValue &&
+            elapsed.TotalSeconds > maxSeconds)
         {
-            var elapsed = Stopwatch.GetElapsedTime(cache.Ticks);
-            if (elapsed.TotalSeconds > maxSeconds)
-            {
-                return false;
-            }
+            return false;
+        }
+
+        if (TryParseDirectiveValue(cacheControl, "min-fresh=", out var minFresh) &&
+            elapsed.TotalSeconds + minFresh > maxSeconds)
+        {
+            return false;
         }
 
         timeStamp = cache.Value;
@@ -261,6 +273,35 @@ static bool TryParseDirectiveValue(string header, string directive, out int seco
         return int.TryParse(span[..end], out seconds);
     }
 
+    static bool HasDirective(StringValues cacheControl, string directive)
+    {
+        foreach (var value in cacheControl)
+        {
+            if (value is not null &&
+                value.Contains(directive, StringComparison.OrdinalIgnoreCase))
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    static bool TryParseDirectiveValue(StringValues cacheControl, string directive, out int seconds)
+    {
+        foreach (var value in cacheControl)
+        {
+            if (value is not null &&
+                TryParseDirectiveValue(value, directive, out seconds))
+            {
+                return true;
+            }
+        }
+
+        seconds = 0;
+        return false;
+    }
+
     [LoggerMessage(Message = "Delta {path}: Using cached timestamp")]
     static partial void LogTimeStampCacheHit(ILogger logger, LogLevel level, string path);
 

src/DeltaTests/MiddlewareTests.Combinations_suffixFunc=False_nullSuffixFunc=False_get=False_ifNoneMatch=False_sameIfNoneMatch=False_etag=False_executeFunc=False_trueExecuteFunc=False_immutable=False_noCache=False_minFresh=True.verified.txt

@@ -0,0 +1,35 @@
+{
+  target: {
+    notModified: false,
+    context: {
+      Request: {
+        Headers: {
+          Cache-Control: min-fresh=5
+        }
+      },
+      Response: {
+        StatusCode: OK,
+        Headers: {
+          Delta-No304: Request method is not GET
+        }
+      }
+    }
+  },
+  log: {
+    Information: Delta /path: No 304. Request method is not GET,
+    EventId: {
+      Name: LogNo304
+    },
+    State: [
+      {
+        path: /path
+      },
+      {
+        reason: Request method is not GET
+      },
+      {
+        {OriginalFormat}: Delta {path}: No 304. {reason}
+      }
+    ]
+  }
+}

src/DeltaTests/MiddlewareTests.Combinations_suffixFunc=False_nullSuffixFunc=False_get=False_ifNoneMatch=False_sameIfNoneMatch=False_etag=False_executeFunc=False_trueExecuteFunc=False_immutable=False_noCache=True_minFresh=True.verified.txt

@@ -0,0 +1,35 @@
+{
+  target: {
+    notModified: false,
+    context: {
+      Request: {
+        Headers: {
+          Cache-Control: no-cache, min-fresh=5
+        }
+      },
+      Response: {
+        StatusCode: OK,
+        Headers: {
+          Delta-No304: Request method is not GET
+        }
+      }
+    }
+  },
+  log: {
+    Information: Delta /path: No 304. Request method is not GET,
+    EventId: {
+      Name: LogNo304
+    },
+    State: [
+      {
+        path: /path
+      },
+      {
+        reason: Request method is not GET
+      },
+      {
+        {OriginalFormat}: Delta {path}: No 304. {reason}
+      }
+    ]
+  }
+}

src/DeltaTests/MiddlewareTests.Combinations_suffixFunc=False_nullSuffixFunc=False_get=False_ifNoneMatch=False_sameIfNoneMatch=False_etag=False_executeFunc=False_trueExecuteFunc=False_immutable=True_noCache=False_minFresh=True.verified.txt

@@ -0,0 +1,36 @@
+{
+  target: {
+    notModified: false,
+    context: {
+      Request: {
+        Headers: {
+          Cache-Control: min-fresh=5
+        }
+      },
+      Response: {
+        StatusCode: OK,
+        Headers: {
+          Cache-Control: public, max-age=31536000, immutable,
+          Delta-No304: Request method is not GET
+        }
+      }
+    }
+  },
+  log: {
+    Information: Delta /path: No 304. Request method is not GET,
+    EventId: {
+      Name: LogNo304
+    },
+    State: [
+      {
+        path: /path
+      },
+      {
+        reason: Request method is not GET
+      },
+      {
+        {OriginalFormat}: Delta {path}: No 304. {reason}
+      }
+    ]
+  }
+}

src/DeltaTests/MiddlewareTests.Combinations_suffixFunc=False_nullSuffixFunc=False_get=False_ifNoneMatch=False_sameIfNoneMatch=False_etag=False_executeFunc=False_trueExecuteFunc=False_immutable=True_noCache=True_minFresh=True.verified.txt

@@ -0,0 +1,36 @@
+{
+  target: {
+    notModified: false,
+    context: {
+      Request: {
+        Headers: {
+          Cache-Control: no-cache, min-fresh=5
+        }
+      },
+      Response: {
+        StatusCode: OK,
+        Headers: {
+          Cache-Control: public, max-age=31536000, immutable,
+          Delta-No304: Request method is not GET
+        }
+      }
+    }
+  },
+  log: {
+    Information: Delta /path: No 304. Request method is not GET,
+    EventId: {
+      Name: LogNo304
+    },
+    State: [
+      {
+        path: /path
+      },
+      {
+        reason: Request method is not GET
+      },
+      {
+        {OriginalFormat}: Delta {path}: No 304. {reason}
+      }
+    ]
+  }
+}

src/DeltaTests/MiddlewareTests.Combinations_suffixFunc=False_nullSuffixFunc=False_get=False_ifNoneMatch=False_sameIfNoneMatch=False_etag=False_executeFunc=False_trueExecuteFunc=True_immutable=False_noCache=False_minFresh=True.verified.txt

@@ -0,0 +1,35 @@
+{
+  target: {
+    notModified: false,
+    context: {
+      Request: {
+        Headers: {
+          Cache-Control: min-fresh=5
+        }
+      },
+      Response: {
+        StatusCode: OK,
+        Headers: {
+          Delta-No304: Request method is not GET
+        }
+      }
+    }
+  },
+  log: {
+    Information: Delta /path: No 304. Request method is not GET,
+    EventId: {
+      Name: LogNo304
+    },
+    State: [
+      {
+        path: /path
+      },
+      {
+        reason: Request method is not GET
+      },
+      {
+        {OriginalFormat}: Delta {path}: No 304. {reason}
+      }
+    ]
+  }
+}

src/DeltaTests/MiddlewareTests.Combinations_suffixFunc=False_nullSuffixFunc=False_get=False_ifNoneMatch=False_sameIfNoneMatch=False_etag=False_executeFunc=False_trueExecuteFunc=True_immutable=False_noCache=True_minFresh=True.verified.txt

@@ -0,0 +1,35 @@
+{
+  target: {
+    notModified: false,
+    context: {
+      Request: {
+        Headers: {
+          Cache-Control: no-cache, min-fresh=5
+        }
+      },
+      Response: {
+        StatusCode: OK,
+        Headers: {
+          Delta-No304: Request method is not GET
+        }
+      }
+    }
+  },
+  log: {
+    Information: Delta /path: No 304. Request method is not GET,
+    EventId: {
+      Name: LogNo304
+    },
+    State: [
+      {
+        path: /path
+      },
+      {
+        reason: Request method is not GET
+      },
+      {
+        {OriginalFormat}: Delta {path}: No 304. {reason}
+      }
+    ]
+  }
+}

src/DeltaTests/MiddlewareTests.Combinations_suffixFunc=False_nullSuffixFunc=False_get=False_ifNoneMatch=False_sameIfNoneMatch=False_etag=False_executeFunc=False_trueExecuteFunc=True_immutable=True_noCache=False_minFresh=True.verified.txt

@@ -0,0 +1,36 @@
+{
+  target: {
+    notModified: false,
+    context: {
+      Request: {
+        Headers: {
+          Cache-Control: min-fresh=5
+        }
+      },
+      Response: {
+        StatusCode: OK,
+        Headers: {
+          Cache-Control: public, max-age=31536000, immutable,
+          Delta-No304: Request method is not GET
+        }
+      }
+    }
+  },
+  log: {
+    Information: Delta /path: No 304. Request method is not GET,
+    EventId: {
+      Name: LogNo304
+    },
+    State: [
+      {
+        path: /path
+      },
+      {
+        reason: Request method is not GET
+      },
+      {
+        {OriginalFormat}: Delta {path}: No 304. {reason}
+      }
+    ]
+  }
+}