Default RoleInstance to HostName (Azure#23592)

* default to hostname

* fix breaking tests

* update comment

* minor

* undo comment

* resolve PR comment

Author: vishweshbankwar

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/TelemetryPartA.cs

@@ -1,10 +1,11 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
+using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Globalization;
-
+using System.Net;
 using Azure.Monitor.OpenTelemetry.Exporter.Models;
 
 using OpenTelemetry.Logs;
@@ -155,6 +156,18 @@ internal static void InitRoleInfo(Resource resource)
             {
                 RoleName = serviceName;
             }
+
+            if (RoleInstance == null)
+            {
+                try
+                {
+                    RoleInstance = Dns.GetHostName();
+                }
+                catch (Exception ex)
+                {
+                    AzureMonitorExporterEventSource.Log.Write($"ErrorInitializingRoleInstanceToHostName{EventLevelSuffix.Error}", $"{ex.ToInvariantString()}");
+                }
+            }
         }
 
         internal static string FormatUtcTimestamp(System.DateTime utcTimestamp)

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

@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Globalization;
+using System.Net;
 using Xunit;
 
 using Azure.Monitor.OpenTelemetry.Exporter.Models;
@@ -56,7 +57,7 @@ public void InitRoleInfo_Default()
             TelemetryPartA.InitRoleInfo(resource);
 
             Assert.StartsWith("unknown_service", TelemetryPartA.RoleName);
-            Assert.Null(TelemetryPartA.RoleInstance);
+            Assert.Equal(Dns.GetHostName(), TelemetryPartA.RoleInstance);
         }
 
         [Fact]
@@ -66,7 +67,7 @@ public void InitRoleInfo_ServiceName()
             TelemetryPartA.InitRoleInfo(resource);
 
             Assert.Equal("my-service", TelemetryPartA.RoleName);
-            Assert.Null(TelemetryPartA.RoleInstance);
+            Assert.Equal(Dns.GetHostName(), TelemetryPartA.RoleInstance);
         }
 
         [Fact]
@@ -86,7 +87,7 @@ public void InitRoleInfo_ServiceNamespace()
             TelemetryPartA.InitRoleInfo(resource);
 
             Assert.StartsWith("my-namespace.unknown_service", TelemetryPartA.RoleName);
-            Assert.Null(TelemetryPartA.RoleInstance);
+            Assert.Equal(Dns.GetHostName(), TelemetryPartA.RoleInstance);
         }
 
         [Fact]
@@ -128,7 +129,7 @@ public void GeneratePartAEnvelope_DefaultActivity_DefaultResource()
             Assert.Equal("RemoteDependency", telemetryItem.Name);
             Assert.Equal(TelemetryPartA.FormatUtcTimestamp(activity.StartTimeUtc), telemetryItem.Time);
             Assert.StartsWith("unknown_service", telemetryItem.Tags[ContextTagKeys.AiCloudRole.ToString()]);
-            Assert.Null(telemetryItem.Tags[ContextTagKeys.AiCloudRoleInstance.ToString()]);
+            Assert.Equal(Dns.GetHostName(), telemetryItem.Tags[ContextTagKeys.AiCloudRoleInstance.ToString()]);
             Assert.NotNull(telemetryItem.Tags[ContextTagKeys.AiOperationId.ToString()]);
             Assert.NotNull(telemetryItem.Tags[ContextTagKeys.AiInternalSdkVersion.ToString()]);
             Assert.Throws<KeyNotFoundException>(() => telemetryItem.Tags[ContextTagKeys.AiOperationParentId.ToString()]);
@@ -177,7 +178,7 @@ public void GeneratePartAEnvelope_Activity_WithParentSpanId()
             Assert.Equal("RemoteDependency", telemetryItem.Name);
             Assert.Equal(TelemetryPartA.FormatUtcTimestamp(activity.StartTimeUtc), telemetryItem.Time);
             Assert.StartsWith("unknown_service", telemetryItem.Tags[ContextTagKeys.AiCloudRole.ToString()]);
-            Assert.Null(telemetryItem.Tags[ContextTagKeys.AiCloudRoleInstance.ToString()]);
+            Assert.Equal(Dns.GetHostName(), telemetryItem.Tags[ContextTagKeys.AiCloudRoleInstance.ToString()]);
             Assert.NotNull(telemetryItem.Tags[ContextTagKeys.AiOperationId.ToString()]);
             Assert.NotNull(telemetryItem.Tags[ContextTagKeys.AiInternalSdkVersion.ToString()]);
             Assert.Equal(activity.ParentSpanId.ToHexString(), telemetryItem.Tags[ContextTagKeys.AiOperationParentId.ToString()]);
@@ -322,6 +323,42 @@ public void AiUserAgentIsNullByDefault()
             Assert.Null(telemetryItem.Tags["ai.user.userAgent"]);
         }
 
+        [Fact]
+        public void RoleInstanceIsSetToHostNameByDefault()
+        {
+            using ActivitySource activitySource = new ActivitySource(ActivitySourceName);
+            using var activity = activitySource.StartActivity(
+                ActivityName,
+                ActivityKind.Server,
+                null,
+                startTime: DateTime.UtcNow);
+            var resource = CreateTestResource();
+
+            var monitorTags = AzureMonitorConverter.EnumerateActivityTags(activity);
+
+            var telemetryItem = TelemetryPartA.GetTelemetryItem(activity, ref monitorTags, resource, null);
+
+            Assert.Equal(Dns.GetHostName(), telemetryItem.Tags[ContextTagKeys.AiCloudRoleInstance.ToString()]);
+        }
+
+        [Fact]
+        public void RoleInstanceIsNotOverwrittenIfSetViaServiceInstanceId()
+        {
+            using ActivitySource activitySource = new ActivitySource(ActivitySourceName);
+            using var activity = activitySource.StartActivity(
+                ActivityName,
+                ActivityKind.Server,
+                null,
+                startTime: DateTime.UtcNow);
+            var resource = CreateTestResource(null, null, "serviceinstance");
+
+            var monitorTags = AzureMonitorConverter.EnumerateActivityTags(activity);
+
+            var telemetryItem = TelemetryPartA.GetTelemetryItem(activity, ref monitorTags, resource, null);
+
+            Assert.Equal("serviceinstance", telemetryItem.Tags[ContextTagKeys.AiCloudRoleInstance.ToString()]);
+        }
+
         /// <summary>
         /// If SERVICE.NAME is not defined, it will fall-back to "unknown_service".
         /// (https://github.com/open-telemetry/opentelemetry-specification/tree/main/specification/resource/semantic_conventions#semantic-attributes-with-sdk-provided-default-value).