[AzureMonitorExporter] Subscribe Statsbeat MeterProvider to distro Network SDKStats meter (Azure#60209)

* [AzureMonitorExporter] Subscribe Statsbeat MeterProvider to distro Network SDKStats meter

The Microsoft.OpenTelemetry distro publishes Network SDKStats on a meter named
`MicrosoftOpenTelemetryNetworkSdkStatsMeter` when it runs with a non-Azure-Monitor
exporter (e.g. the Agent365 exporter), where the distro owns the network signal
instead of the exporter's Breeze transmitter.

This change:

- Adds `StatsbeatConstants.DistroNetworkSdkStatsMeterName` constant.
- Subscribes the Statsbeat MeterProvider in `AzureMonitorStatsbeat` to the new
  meter via `.AddMeter(...)` alongside the existing Attach, Feature, and distro
  Feature meters so distro-emitted Network stats flow through the existing
  Statsbeat cadence.

This is the Network analog of Azure#59529 (distro Feature SDKStats meter).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* [AzureMonitorExporter] Add sentinel test for distro SDKStats meter subscriptions

Adds a regression test guarding the Statsbeat MeterProvider's .AddMeter(...) subscriptions to the distro-owned Feature and Network SDKStats meters. The test publishes an observable instrument on each distro meter and asserts ForceFlush collects it, failing if a .AddMeter(StatsbeatConstants.Distro*SdkStatsMeterName) entry is removed or a meter constant is renamed.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: JacksonWeber

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/CHANGELOG.md

@@ -6,6 +6,8 @@
 
 - Added support for the Microsoft OpenTelemetry distro's SDK statistics: a new internal meter subscription and an AppContext switch (`Azure.Monitor.OpenTelemetry.Exporter.RouteSdkStatsToDistroEndpoint`) that lets the distro redirect SDK statistics to its own ingestion path. The ingestion destination and an on/off signal are resolved at startup by fetching a remote configuration; on success the configured destination is used, an explicit remote disable signal turns SDK statistics off, and any other outcome falls back to the existing region-derived ingestion endpoint so SDK statistics keep flowing. The AppContext switch has no effect on Statsbeat for callers that do not opt in.
 
+- Subscribed the Statsbeat `MeterProvider` to the Microsoft OpenTelemetry distro's Network SDKStats meter (`MicrosoftOpenTelemetryNetworkSdkStatsMeter`) so distro-emitted Network statistics flow through the existing Statsbeat cadence when the distro runs with a non-Azure-Monitor exporter.
+
 ### Breaking Changes
 
 ### Bugs Fixed

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/Statsbeat/AzureMonitorStatsbeat.cs

@@ -206,6 +206,7 @@ private void BuildMeterProvider(string connectionString)
                 .AddMeter(StatsbeatConstants.FeatureStatsbeatMeterName)
                 .AddMeter(StatsbeatConstants.DistroFeatureSdkStatsMeterName)
                 .AddMeter(StatsbeatConstants.NetworkSdkStatsMeterName)
+                .AddMeter(StatsbeatConstants.DistroNetworkSdkStatsMeterName)
                 .AddReader(new PeriodicExportingMetricReader(new AzureMonitorMetricExporter(exporterOptions), StatsbeatConstants.NetworkStatsbeatInterval)
                 { TemporalityPreference = MetricReaderTemporalityPreference.Delta })
                 .Build();

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/Statsbeat/StatsbeatConstants.cs

@@ -150,5 +150,15 @@ internal static class StatsbeatConstants
         /// flow through to the same Statsbeat ingestion resource.
         /// </summary>
         internal const string DistroFeatureSdkStatsMeterName = "MicrosoftOpenTelemetryFeatureSdkStatsMeter";
+
+        /// <summary>
+        /// Meter name used by the Microsoft OpenTelemetry distro to publish distro-owned Network
+        /// SDKStats. When the distro runs with a non-Azure-Monitor exporter (e.g. the Agent365
+        /// exporter), the distro owns the Network signal and records request success/failure,
+        /// retry, throttle, duration, and exception counters on this meter. The Statsbeat
+        /// <c>MeterProvider</c> subscribes to it so those measurements flow through the same
+        /// Statsbeat ingestion resource as the Attach and Feature signals.
+        /// </summary>
+        internal const string DistroNetworkSdkStatsMeterName = "MicrosoftOpenTelemetryNetworkSdkStatsMeter";
     }
 }

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/tests/Azure.Monitor.OpenTelemetry.Exporter.Tests/StatsbeatTests.cs

@@ -8,6 +8,8 @@
 using Azure.Monitor.OpenTelemetry.Exporter.Internals.ConnectionString;
 using Azure.Monitor.OpenTelemetry.Exporter.Internals.Statsbeat;
 using Azure.Monitor.OpenTelemetry.Exporter.Tests.CommonTestFramework;
+using OpenTelemetry;
+using OpenTelemetry.Metrics;
 using Xunit;
 
 namespace Azure.Monitor.OpenTelemetry.Exporter.Tests
@@ -107,5 +109,46 @@ public void ConstructingAzureMonitorMetricExporter_TriggersStatsbeatSideEffect()
 
             Assert.Contains(StatsbeatConstants.AttachStatsbeatMeterName, observedMeters);
         }
+
+        public static TheoryData<string> DistroSdkStatsMeterNames => new()
+        {
+            StatsbeatConstants.DistroFeatureSdkStatsMeterName,
+            StatsbeatConstants.DistroNetworkSdkStatsMeterName,
+        };
+
+        [Theory]
+        [MemberData(nameof(DistroSdkStatsMeterNames))]
+        public void StatsbeatMeterProvider_SubscribesToDistroSdkStatsMeters(string distroMeterName)
+        {
+            // SENTINEL TEST. The Microsoft.OpenTelemetry distro emits distro-owned Feature and
+            // Network SDKStats on dedicated meters (e.g. when running with a non-Azure-Monitor
+            // exporter). The Statsbeat MeterProvider must subscribe to those meters via
+            // .AddMeter(...) so the measurements flow through the existing Statsbeat cadence.
+            //
+            // If this test fails, an .AddMeter(StatsbeatConstants.Distro*SdkStatsMeterName) entry
+            // in AzureMonitorStatsbeat.BuildMeterProvider was removed or the meter constant was
+            // renamed, silently dropping distro-emitted SDKStats.
+
+            var connectionString = "InstrumentationKey=00000000-0000-0000-0000-000000000000;IngestionEndpoint=https://eastus.in.applicationinsights.azure.com/";
+            var connectionStringVars = ConnectionStringParser.GetValues(connectionString);
+
+            using var statsbeat = new AzureMonitorStatsbeat(connectionStringVars, new MockPlatform());
+            Assert.NotNull(statsbeat._statsbeatMeterProvider);
+
+            // Publish an observable instrument on the distro meter. If the Statsbeat
+            // MeterProvider subscribed to this meter, ForceFlush collects the instrument and
+            // invokes the callback; otherwise the callback never runs.
+            using var distroMeter = new Meter(distroMeterName);
+            var callbackInvoked = false;
+            distroMeter.CreateObservableGauge("test.sentinel", () =>
+            {
+                callbackInvoked = true;
+                return new Measurement<long>(1);
+            });
+
+            statsbeat._statsbeatMeterProvider!.ForceFlush();
+
+            Assert.True(callbackInvoked, $"Statsbeat MeterProvider did not subscribe to '{distroMeterName}'.");
+        }
     }
 }