[Exporter.Prometheus] Use dictionary to key views

src/OpenTelemetry.Exporter.Prometheus.AspNetCore/OpenTelemetry.Exporter.Prometheus.AspNetCore.csproj

@@ -27,6 +27,7 @@
     <Compile Include="$(RepoRoot)\src\Shared\CharExtensions.cs" Link="Includes\CharExtensions.cs" />
     <Compile Include="$(RepoRoot)\src\Shared\ExceptionExtensions.cs" Link="Includes\ExceptionExtensions.cs" />
     <Compile Include="$(RepoRoot)\src\Shared\Guard.cs" Link="Includes\Guard.cs" />
+    <Compile Include="$(RepoRoot)\src\Shared\Shims\Lock.cs" Link="Includes\Shims\Lock.cs" />
     <Compile Include="$(RepoRoot)\src\Shared\Shims\NullableAttributes.cs" Link="Includes\Shims\NullableAttributes.cs" />
     <Compile Include="$(RepoRoot)\src\Shared\StopwatchExtensions.cs" Link="Includes\StopwatchExtensions.cs" />
   </ItemGroup>

src/OpenTelemetry.Exporter.Prometheus.AspNetCore/PrometheusExporterMiddleware.cs

@@ -79,13 +79,13 @@ public async Task InvokeAsync(HttpContext httpContext)
 
             var protocol = Negotiate(requestHeaders);
 
-            var collectionResponse = await this.exporter.CollectionManager.EnterCollect(protocol.IsOpenMetrics);
+            var collectionResponse = await this.exporter.CollectionManager.EnterCollect(protocol);
 
             try
             {
                 linkedCts.Token.ThrowIfCancellationRequested();
 
-                var dataView = protocol.IsOpenMetrics ? collectionResponse.OpenMetricsView : collectionResponse.PlainTextView;
+                var dataView = collectionResponse.View;
 
                 response.StatusCode = StatusCodes.Status200OK;
 
@@ -116,7 +116,7 @@ public async Task InvokeAsync(HttpContext httpContext)
             }
             finally
             {
-                this.exporter.CollectionManager.ExitCollect();
+                this.exporter.CollectionManager.ExitCollect(protocol);
             }
         }
         catch (Exception ex)
@@ -272,7 +272,7 @@ private static bool TryParse(
         if (version is null)
         {
             // Use the oldest version if no version preference was specified
-            version = isOpenMetrics ? PrometheusProtocol.OpenMetricsV0 : PrometheusProtocol.PrometheusVersion0;
+            version = isOpenMetrics ? PrometheusProtocol.OpenMetricsV0 : PrometheusProtocol.PrometheusV0;
         }
         else if (version.Major is not > 0)
         {
@@ -286,6 +286,9 @@ private static bool TryParse(
         }
 
         protocol = new(mediaType, escaping, version, isOpenMetrics);
+
+        protocol.Value.Validate();
+
         return true;
     }
 

src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusHeadersParser.cs

@@ -119,7 +119,7 @@ internal static PrometheusProtocol Negotiate(string? contentType)
             if (version is null)
             {
                 // Use the oldest version if no version preference was specified
-                version = isOpenMetrics ? PrometheusProtocol.OpenMetricsV0 : PrometheusProtocol.PrometheusVersion0;
+                version = isOpenMetrics ? PrometheusProtocol.OpenMetricsV0 : PrometheusProtocol.PrometheusV0;
             }
             else if (version.Major is not > 0)
             {
@@ -138,6 +138,8 @@ internal static PrometheusProtocol Negotiate(string? contentType)
                 version,
                 isOpenMetrics);
 
+            protocol.Validate();
+
             preferences.Add((protocol, quality));
         }