MaxConcurrentRequests range check

Author: DylanDmitri

src/Middleware/RequestThrottling/src/RequestThrottlingMiddleware.cs

@@ -35,18 +35,14 @@ public RequestThrottlingMiddleware(RequestDelegate next, ILoggerFactory loggerFa
             {
                 throw new ArgumentException("The value of 'options.MaxConcurrentRequests' must be specified.", nameof(options));
             }
-            if (_requestThrottlingOptions.MaxConcurrentRequests < 0)
+            if (_requestThrottlingOptions.MaxConcurrentRequests <= 0)
             {
-                throw new ArgumentException("The value of 'options.MaxConcurrentRequests' must be a positive integer.", nameof(options));
+                throw new ArgumentOutOfRangeException(nameof(options), "The value of `options.MaxConcurrentRequests` must be a positive integer.");
             }
             if (_requestThrottlingOptions.RequestQueueLimit < 0)
             {
                 throw new ArgumentException("The value of 'options.RequestQueueLimit' must be a positive integer.", nameof(options));
             }
-            if (_requestThrottlingOptions.MaxConcurrentRequests <= 0)
-            {
-                throw new ArgumentOutOfRangeException(nameof(options), "The value of `options.MaxConcurrentRequests` must be a positive integer.");
-            }
 
             if (_requestThrottlingOptions.OnRejected == null)
             {
@@ -55,9 +51,15 @@ public RequestThrottlingMiddleware(RequestDelegate next, ILoggerFactory loggerFa
 
             _next = next;
             _logger = loggerFactory.CreateLogger<RequestThrottlingMiddleware>();
-            _requestQueue = new TailDrop(
-                _requestThrottlingOptions.MaxConcurrentRequests.Value,
-                _requestThrottlingOptions.RequestQueueLimit);
+
+            if (_requestThrottlingOptions.ServerAlwaysBlocks)
+            {
+                _requestQueue = new TailDrop(0, _requestThrottlingOptions.RequestQueueLimit);
+            }
+            else
+            {
+                _requestQueue = new TailDrop(_requestThrottlingOptions.MaxConcurrentRequests.Value, _requestThrottlingOptions.RequestQueueLimit);
+            }
         }
 
         /// <summary>

src/Middleware/RequestThrottling/src/RequestThrottlingOptions.cs

@@ -33,5 +33,10 @@ public class RequestThrottlingOptions
         {
             return Task.CompletedTask;
         };
+
+        /// <summary>
+        /// For internal testing only. If true, no requests will enter the server.
+        /// </summary>
+        internal bool ServerAlwaysBlocks { get; set; } = false;
     }
 }

src/Middleware/RequestThrottling/test/TestUtils.cs

@@ -15,10 +15,12 @@ public static RequestThrottlingMiddleware CreateTestMiddleware(int? maxConcurren
         {
             var options = new RequestThrottlingOptions
             {
-                MaxConcurrentRequests = maxConcurrentRequests,
+                MaxConcurrentRequests = maxConcurrentRequests == 0 ? 999 : maxConcurrentRequests,
                 RequestQueueLimit = requestQueueLimit
             };
 
+            options.ServerAlwaysBlocks = maxConcurrentRequests == 0;
+
             if (onRejected != null)
             {
                 options.OnRejected = onRejected;