[AzureMonitorExporter] refactor how EnvironmentVariables are read

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/Diagnostics/AzureMonitorExporterEventSource.cs

@@ -419,5 +419,17 @@ public void FailedToAddLogAttribute(string key, Exception ex)
 
         [Event(41, Message = "An exception {1} occurred while adding the log attribute associated with the key {0}", Level = EventLevel.Warning)]
         public void FailedToAddLogAttribute(string key, string exceptionMessage) => WriteEvent(41, key, exceptionMessage);
+
+        [NonEvent]
+        public void FailedToReadEnvironmentVariables(Exception ex)
+        {
+            if (IsEnabled(EventLevel.Warning))
+            {
+                FailedToReadEnvironmentVariables(ex.FlattenException().ToInvariantString());
+            }
+        }
+
+        [Event(42, Message = "Failed to read environment variables due to an exception. This may prevent the Exporter from initializing. {0}", Level = EventLevel.Warning)]
+        public void FailedToReadEnvironmentVariables(string errorMessage) => WriteEvent(42, errorMessage);
     }
 }

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/PersistentStorage/StorageHelper.cs

@@ -2,7 +2,6 @@
 // Licensed under the MIT License.
 
 using System;
-using System.Collections;
 using System.IO;
 using System.Runtime.InteropServices;
 using Azure.Monitor.OpenTelemetry.Exporter.Internals.Platform;
@@ -30,19 +29,18 @@ internal static string GetStorageDirectory(IPlatform platform, string? configure
         internal static string? GetDefaultStorageDirectory(IPlatform platform)
         {
             string? dirPath;
-            IDictionary environmentVars = platform.GetEnvironmentVariables();
 
             if (platform.IsOSPlatform(OSPlatform.Windows))
             {
-                if (TryCreateTelemetryDirectory(platform: platform, path: environmentVars[EnvironmentVariableConstants.LOCALAPPDATA]?.ToString(), createdDirectoryPath: out dirPath)
-                    || TryCreateTelemetryDirectory(platform: platform, path: environmentVars[EnvironmentVariableConstants.TEMP]?.ToString(), createdDirectoryPath: out dirPath))
+                if (TryCreateTelemetryDirectory(platform: platform, path: platform.GetEnvironmentVariable(EnvironmentVariableConstants.LOCALAPPDATA), createdDirectoryPath: out dirPath)
+                    || TryCreateTelemetryDirectory(platform: platform, path: platform.GetEnvironmentVariable(EnvironmentVariableConstants.TEMP), createdDirectoryPath: out dirPath))
                 {
                     return dirPath;
                 }
             }
             else
             {
-                if (TryCreateTelemetryDirectory(platform: platform, path: environmentVars[EnvironmentVariableConstants.TMPDIR]?.ToString(), createdDirectoryPath: out dirPath)
+                if (TryCreateTelemetryDirectory(platform: platform, path: platform.GetEnvironmentVariable(EnvironmentVariableConstants.TMPDIR), createdDirectoryPath: out dirPath)
                     || TryCreateTelemetryDirectory(platform: platform, path: "/var/tmp/", createdDirectoryPath: out dirPath)
                     || TryCreateTelemetryDirectory(platform: platform, path: "/tmp/", createdDirectoryPath: out dirPath))
                 {

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/Platform/DefaultPlatform.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections;
+using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
 using System.Runtime.InteropServices;
@@ -12,9 +13,22 @@ namespace Azure.Monitor.OpenTelemetry.Exporter.Internals.Platform
 {
     internal class DefaultPlatform : IPlatform
     {
-        public string? GetEnvironmentVariable(string name) => Environment.GetEnvironmentVariable(name);
+        private readonly IDictionary _environmentVariables;
 
-        public IDictionary GetEnvironmentVariables() => Environment.GetEnvironmentVariables();
+        public DefaultPlatform()
+        {
+            try
+            {
+                _environmentVariables = Environment.GetEnvironmentVariables();
+            }
+            catch (Exception ex)
+            {
+                AzureMonitorExporterEventSource.Log.FailedToReadEnvironmentVariables(ex);
+                _environmentVariables = new Dictionary<string, object>();
+            }
+        }
+
+        public string? GetEnvironmentVariable(string name) => _environmentVariables[name]?.ToString();
 
         public string GetOSPlatformName()
         {

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/EnvironmentVariableConstants.cs → sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/Platform/EnvironmentVariableConstants.cs

@@ -1,7 +1,7 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
-namespace Azure.Monitor.OpenTelemetry.Exporter.Internals
+namespace Azure.Monitor.OpenTelemetry.Exporter.Internals.Platform
 {
     internal static class EnvironmentVariableConstants
     {

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/Platform/IPlatform.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
-using System.Collections;
 using System.Runtime.InteropServices;
 
 namespace Azure.Monitor.OpenTelemetry.Exporter.Internals.Platform
@@ -15,8 +14,6 @@ internal interface IPlatform
         /// <returns></returns>
         public string? GetEnvironmentVariable(string name);
 
-        public IDictionary GetEnvironmentVariables();
-
         public bool IsOSPlatform(OSPlatform osPlatform);
 
         public string GetOSPlatformName();

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/ResourceExtensions.cs

@@ -6,6 +6,7 @@
 using System.Linq;
 using System.Net;
 using Azure.Monitor.OpenTelemetry.Exporter.Internals.Diagnostics;
+using Azure.Monitor.OpenTelemetry.Exporter.Internals.Platform;
 using Azure.Monitor.OpenTelemetry.Exporter.Models;
 using OpenTelemetry.Resources;
 

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/TransmitterFactory.cs

@@ -15,7 +15,6 @@ namespace Azure.Monitor.OpenTelemetry.Exporter.Internals
     internal sealed class TransmitterFactory
     {
         public static readonly TransmitterFactory Instance = new();
-        public static readonly IPlatform platform = new DefaultPlatform();
 
         internal readonly Dictionary<string, AzureMonitorTransmitter> _transmitters = new();
         private readonly object _lockObj = new();
@@ -30,7 +29,7 @@ public AzureMonitorTransmitter Get(AzureMonitorExporterOptions azureMonitorExpor
                 {
                     if (!_transmitters.TryGetValue(key, out transmitter))
                     {
-                        transmitter = new AzureMonitorTransmitter(azureMonitorExporterOptions, platform);
+                        transmitter = new AzureMonitorTransmitter(azureMonitorExporterOptions, new DefaultPlatform());
 
                         _transmitters.Add(key, transmitter);
                     }

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/tests/Azure.Monitor.OpenTelemetry.Exporter.Tests/CommonTestFramework/MockPlatform.cs

@@ -2,7 +2,6 @@
 // Licensed under the MIT License.
 
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Runtime.InteropServices;
 using Azure.Monitor.OpenTelemetry.Exporter.Internals.Platform;
@@ -24,8 +23,6 @@ internal class MockPlatform : IPlatform
 
         public string? GetEnvironmentVariable(string name) => environmentVariables.TryGetValue(name, out var value) ? value : null;
 
-        public IDictionary GetEnvironmentVariables() => environmentVariables;
-
         public string GetOSPlatformName() => OSPlatformName;
 
         public bool IsOSPlatform(OSPlatform osPlatform) => IsOsPlatformFunc(osPlatform);

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

@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.Net;
 using Azure.Monitor.OpenTelemetry.Exporter.Internals;
+using Azure.Monitor.OpenTelemetry.Exporter.Internals.Platform;
 using Azure.Monitor.OpenTelemetry.Exporter.Models;
 using OpenTelemetry.Resources;
 using Xunit;