Clarify some log messages and comments

Author: amcasey

src/Servers/Kestrel/Core/src/Internal/Http2/Http2Connection.cs

@@ -46,13 +46,13 @@ internal sealed partial class Http2Connection : IHttp2StreamLifetimeHandler, IHt
     private const int MaxStreamPoolSize = 100;
     private const long StreamPoolExpiryTicks = TimeSpan.TicksPerSecond * 5;
 
-    private const string EnhanceYourCalmMaximumCountProperty = "Microsoft.AspNetCore.Server.Kestrel.Http2.EnhanceYourCalmCount";
+    private const string MaximumEnhanceYourCalmCountProperty = "Microsoft.AspNetCore.Server.Kestrel.Http2.MaxEnhanceYourCalmCount";
 
-    private static readonly int _enhanceYourCalmMaximumCount = GetEnhanceYourCalmMaximumCount();
+    private static readonly int _enhanceYourCalmMaximumCount = GetMaximumEnhanceYourCalmCount();
 
-    private static int GetEnhanceYourCalmMaximumCount()
+    private static int GetMaximumEnhanceYourCalmCount()
     {
-        var data = AppContext.GetData(EnhanceYourCalmMaximumCountProperty);
+        var data = AppContext.GetData(MaximumEnhanceYourCalmCountProperty);
         if (data is int count)
         {
             return count;
@@ -1290,6 +1290,8 @@ private void AbortStream(int streamId, IOException error)
     void IRequestProcessor.Tick(DateTimeOffset now)
     {
         Input.CancelPendingRead();
+        // We count EYCs over a window of a given length to avoid flagging short-lived bursts.
+        // At the end of each window, reset the count.
         if (IsEnhanceYourCalmEnabled && ++_tickCount % EnhanceYourCalmTickWindowCount == 0)
         {
             Interlocked.Exchange(ref _enhanceYourCalmCount, 0);

src/Servers/Kestrel/Core/src/Internal/Http2/Http2FrameWriter.cs

@@ -105,7 +105,7 @@ public Http2FrameWriter(
         _hpackEncoder = new DynamicHPackEncoder(serviceContext.ServerOptions.AllowResponseHeaderCompression);
 
         _maximumFlowControlQueueSize = ConfiguredMaximumFlowControlQueueSize is null
-            ? 4 * maxStreamsPerConnection
+            ? 4 * maxStreamsPerConnection // 4 is a magic number to give us some padding above the expected maximum size
             : (int)ConfiguredMaximumFlowControlQueueSize;
 
         if (IsMaximumFlowControlQueueSizeEnabled && _maximumFlowControlQueueSize < maxStreamsPerConnection)

src/Servers/Kestrel/Core/src/Internal/Infrastructure/KestrelTrace.Http2.cs

@@ -146,13 +146,13 @@ private static partial class Http2Log
 
         // Highest shared ID is 63. New consecutive IDs start at 64
 
-        [LoggerMessage(64, LogLevel.Debug, @"Connection id ""{ConnectionId}"" aborted since at least ""{Count}"" ENHANCE_YOUR_CALM responses were required per second.", EventName = "Http2TooManyEnhanceYourCalms")]
+        [LoggerMessage(64, LogLevel.Debug, @"Connection id ""{ConnectionId}"" aborted since at least {Count} ENHANCE_YOUR_CALM responses were recorded per second.", EventName = "Http2TooManyEnhanceYourCalms")]
         public static partial void Http2TooManyEnhanceYourCalms(ILogger logger, string connectionId, int count);
 
-        [LoggerMessage(65, LogLevel.Debug, @"Connection id ""{ConnectionId}"" exceeded the output flow control maximum queue size of ""{Count}"".", EventName = "Http2FlowControlQueueOperationsExceeded")]
+        [LoggerMessage(65, LogLevel.Debug, @"Connection id ""{ConnectionId}"" exceeded the output flow control maximum queue size of {Count}.", EventName = "Http2FlowControlQueueOperationsExceeded")]
         public static partial void Http2FlowControlQueueOperationsExceeded(ILogger logger, string connectionId, int count);
 
-        [LoggerMessage(66, LogLevel.Debug, @"Connection id ""{ConnectionId}"" configured maximum flow control queue size ""{Actual}"" is less than the maximum streams per connection ""{Expected}"" - increasing to match.", EventName = "Http2FlowControlQueueMaximumTooLow")]
+        [LoggerMessage(66, LogLevel.Debug, @"Connection id ""{ConnectionId}"" configured maximum flow control queue size {Actual} is less than the maximum streams per connection {Expected}. Increasing configured value to {Expected}.", EventName = "Http2FlowControlQueueMaximumTooLow")]
         public static partial void Http2FlowControlQueueMaximumTooLow(ILogger logger, string connectionId, int expected, int actual);
     }
 }