Fix Npgsql Metrics (dotnet#658)

* Restore disabled counter

This was missed in dotnet#648

Addresses dotnet#645

* Add view to Npgsql's histograms because they are in seconds and not ms.

Fix dotnet#641

Author: eerhardt

src/Components/Aspire.Npgsql.EntityFrameworkCore.PostgreSQL/Aspire.Npgsql.EntityFrameworkCore.PostgreSQL.csproj

@@ -8,6 +8,10 @@
     <PackageIconFullPath>$(SharedDir)PostgreSQL_logo.3colors.540x557.png</PackageIconFullPath>
   </PropertyGroup>
 
+  <ItemGroup>
+    <Compile Include="..\Aspire.Npgsql\NpgsqlCommon.cs" />
+  </ItemGroup>
+  
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.Configuration.Binder" />
     <PackageReference Include="Microsoft.Extensions.Diagnostics.HealthChecks.EntityFrameworkCore" />

src/Components/Aspire.Npgsql.EntityFrameworkCore.PostgreSQL/AspireEFPostgreSqlExtensions.cs

@@ -122,8 +122,7 @@ public static partial class AspireEFPostgreSqlExtensions
                         eventCountersInstrumentationOptions.AddEventSources("Microsoft.EntityFrameworkCore");
                     });
 
-                    // https://github.com/npgsql/npgsql/blob/4c9921de2dfb48fb5a488787fc7422add3553f50/src/Npgsql/MetricsReporter.cs#L48
-                    meterProviderBuilder.AddMeter("Npgsql");
+                    NpgsqlCommon.AddNpgsqlMetrics(meterProviderBuilder);
                 });
         }
 

src/Components/Aspire.Npgsql/AspirePostgreSqlNpgsqlExtensions.cs

@@ -9,7 +9,6 @@
 using Microsoft.Extensions.Diagnostics.HealthChecks;
 using Microsoft.Extensions.Logging;
 using Npgsql;
-using OpenTelemetry.Metrics;
 
 namespace Microsoft.Extensions.Hosting;
 
@@ -98,14 +97,7 @@ private static void AddNpgsqlDataSource(IHostApplicationBuilder builder, string
         if (settings.Metrics)
         {
             builder.Services.AddOpenTelemetry()
-                .WithMetrics(meterProviderBuilder =>
-                {
-                    // https://github.com/npgsql/npgsql/blob/4c9921de2dfb48fb5a488787fc7422add3553f50/src/Npgsql/MetricsReporter.cs#L48
-                    meterProviderBuilder.AddMeter("Npgsql");
-
-                    // disable "prepared_ratio" until https://github.com/dotnet/aspire/issues/629 is fixed.
-                    meterProviderBuilder.AddView(instrumentName: "db.client.commands.prepared_ratio", MetricStreamConfiguration.Drop);
-                });
+                .WithMetrics(NpgsqlCommon.AddNpgsqlMetrics);
         }
     }
 

src/Components/Aspire.Npgsql/NpgsqlCommon.cs

@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using OpenTelemetry.Metrics;
+
+internal static class NpgsqlCommon
+{
+    public static void AddNpgsqlMetrics(MeterProviderBuilder meterProviderBuilder)
+    {
+        double[] secondsBuckets = [0, 0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10];
+
+        // https://github.com/npgsql/npgsql/blob/4c9921de2dfb48fb5a488787fc7422add3553f50/src/Npgsql/MetricsReporter.cs#L48
+        meterProviderBuilder
+            .AddMeter("Npgsql")
+            // Npgsql's histograms are in seconds, not milliseconds.
+            .AddView("db.client.commands.duration",
+                new ExplicitBucketHistogramConfiguration
+                {
+                    Boundaries = secondsBuckets
+                })
+            .AddView("db.client.connections.create_time",
+                new ExplicitBucketHistogramConfiguration
+                {
+                    Boundaries = secondsBuckets
+                });
+    }
+}