Default metrics pool name to Application Name from connection string (#6533)

roji · Copilot · web-flow · commit 8d90c327415f · 2026-04-08T10:38:52.000Z
Closes #6531 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
diff --git a/src/Npgsql/NpgsqlDataSource.cs b/src/Npgsql/NpgsqlDataSource.cs
@@ -127,12 +127,12 @@ internal NpgsqlDataSource(NpgsqlConnectionStringBuilder settings, NpgsqlDataSour
             ConnectionString = settings.ToString();
 
             // The data source name is reported in tracing/metrics, so avoid leaking the password through there.
-            Name = name ?? settings.ToStringWithoutPassword();
+            Name = name ?? settings.ApplicationName ?? settings.ToStringWithoutPassword();
         }
         else
         {
             ConnectionString = settings.ToStringWithoutPassword();
-            Name = name ?? ConnectionString;
+            Name = name ?? settings.ApplicationName ?? ConnectionString;
         }
 
         _password = settings.Password;
diff --git a/test/Npgsql.Tests/MetricTests.cs b/test/Npgsql.Tests/MetricTests.cs
@@ -127,6 +127,29 @@ public async Task ConnectionMax()
         Assert.That(tags["db.client.connection.pool.name"], Is.EqualTo(dataSource.Name));
     }
 
+    [Test]
+    public async Task Pool_name_defaults_to_application_name()
+    {
+        var exportedItems = new List<Metric>();
+        using var meterProvider = Sdk.CreateMeterProviderBuilder()
+            .AddMeter("Npgsql")
+            .AddInMemoryExporter(exportedItems)
+            .Build();
+
+        var applicationName = "MetricsDataSource" + Interlocked.Increment(ref _dataSourceCounter);
+        var dataSourceBuilder = base.CreateDataSourceBuilder();
+        dataSourceBuilder.ConnectionStringBuilder.ApplicationName = applicationName;
+        // Do not set the data source name - this makes the pool name default to the Application Name
+        await using var dataSource = dataSourceBuilder.Build();
+
+        meterProvider.ForceFlush();
+
+        var metric = exportedItems.Single(m => m.Name == "db.client.connection.max");
+        var point = GetFilteredPoints(metric.GetMetricPoints(), dataSource.Name).First();
+        var tags = ToDictionary(point.Tags);
+        Assert.That(tags["db.client.connection.pool.name"], Is.EqualTo(applicationName));
+    }
+
     [Test]
     public async Task Password_does_not_leak_via_datasource_name([Values] bool persistSecurityInfo)
     {
@@ -137,10 +160,9 @@ public async Task Password_does_not_leak_via_datasource_name([Values] bool persi
             .Build();
 
         var dataSourceBuilder = base.CreateDataSourceBuilder();
-        dataSourceBuilder.ConnectionStringBuilder.ApplicationName = "MetricsDataSource" + Interlocked.Increment(ref _dataSourceCounter);
         dataSourceBuilder.ConnectionStringBuilder.PersistSecurityInfo = persistSecurityInfo;
-        // Do not set the data source name - this makes it default to the connection string, but without
-        // the password (even when Persist Security Info is true)
+        // Do not set the data source name or the application name - this makes the pool name default to the
+        // connection string, but without the password (even when Persist Security Info is true)
         await using var dataSource = dataSourceBuilder.Build();
 
         meterProvider.ForceFlush();

Original file line number	Diff line number	Diff line change
`@@ -127,12 +127,12 @@ internal NpgsqlDataSource(NpgsqlConnectionStringBuilder settings, NpgsqlDataSour`
`127`	`127`	`ConnectionString = settings.ToString();`
`128`	`128`
`129`	`129`	`// The data source name is reported in tracing/metrics, so avoid leaking the password through there.`
`130`		`- Name = name ?? settings.ToStringWithoutPassword();`
	`130`	`+ Name = name ?? settings.ApplicationName ?? settings.ToStringWithoutPassword();`
`131`	`131`	`}`
`132`	`132`	`else`
`133`	`133`	`{`
`134`	`134`	`ConnectionString = settings.ToStringWithoutPassword();`
`135`		`- Name = name ?? ConnectionString;`
	`135`	`+ Name = name ?? settings.ApplicationName ?? ConnectionString;`
`136`	`136`	`}`
`137`	`137`
`138`	`138`	`_password = settings.Password;`