Fix dynamic config update

Author: evgenyfedorov2

src/Libraries/Microsoft.Extensions.Telemetry/Sampling/RandomProbabilisticSampler.cs

@@ -20,13 +20,14 @@ namespace Microsoft.Extensions.Diagnostics.Sampling;
 /// </summary>
 internal sealed class RandomProbabilisticSampler : LoggingSampler, IDisposable
 {
+    internal RandomProbabilisticSamplerFilterRule[] LastKnownGoodSamplerRules;
+
 #if NETFRAMEWORK
     private static readonly System.Threading.ThreadLocal<Random> _randomInstance = new(() => new Random());
 #endif
 
     private readonly IDisposable? _samplerOptionsChangeTokenRegistration;
     private readonly LogSamplingRuleSelector<RandomProbabilisticSamplerFilterRule> _ruleSelector;
-    private RandomProbabilisticSamplerFilterRule[] _lastKnownGoodSamplerRules;
     private volatile bool _disposed;
 
     /// <summary>
@@ -37,7 +38,7 @@ public RandomProbabilisticSampler(
         IOptionsMonitor<RandomProbabilisticSamplerOptions> options)
     {
         _ruleSelector = Throw.IfNull(ruleSelector);
-        _lastKnownGoodSamplerRules = Throw.IfNullOrMemberNull(options, options!.CurrentValue).Rules.ToArray();
+        LastKnownGoodSamplerRules = Throw.IfNullOrMemberNull(options, options!.CurrentValue).Rules.ToArray();
         _samplerOptionsChangeTokenRegistration = options.OnChange(OnSamplerOptionsChanged);
     }
 
@@ -70,11 +71,11 @@ private void OnSamplerOptionsChanged(RandomProbabilisticSamplerOptions? updatedO
     {
         if (updatedOptions is null)
         {
-            _lastKnownGoodSamplerRules = Array.Empty<RandomProbabilisticSamplerFilterRule>();
+            LastKnownGoodSamplerRules = Array.Empty<RandomProbabilisticSamplerFilterRule>();
         }
         else
         {
-            _lastKnownGoodSamplerRules = updatedOptions.Rules.ToArray();
+            LastKnownGoodSamplerRules = updatedOptions.Rules.ToArray();
         }
 
         _ruleSelector.InvalidateCache();
@@ -84,7 +85,7 @@ private bool TryApply<TState>(in LogEntry<TState> logEntry, out double probabili
     {
         probability = 0.0;
 
-        RandomProbabilisticSamplerFilterRule? rule = _ruleSelector.Select(_lastKnownGoodSamplerRules, logEntry.Category, logEntry.LogLevel, logEntry.EventId);
+        RandomProbabilisticSamplerFilterRule? rule = _ruleSelector.Select(LastKnownGoodSamplerRules, logEntry.Category, logEntry.LogLevel, logEntry.EventId);
 
         if (rule is null)
         {

src/Libraries/Microsoft.Extensions.Telemetry/Sampling/SamplingLoggerBuilderExtensions.cs

@@ -7,7 +7,6 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Diagnostics.Sampling;
-using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 using Microsoft.Shared.DiagnosticIds;
 using Microsoft.Shared.Diagnostics;
@@ -51,11 +50,17 @@ public static ILoggingBuilder AddRandomProbabilisticSampler(this ILoggingBuilder
         _ = Throw.IfNull(builder);
         _ = Throw.IfNull(configuration);
 
-        _ = builder.Services.AddOptionsWithValidateOnStart<RandomProbabilisticSamplerOptions, RandomProbabilisticSamplerOptionsValidator>();
-        _ = builder.Services.AddSingleton<IConfigureOptions<RandomProbabilisticSamplerOptions>>(
+        _ = builder.Services
+            .AddOptionsWithValidateOnStart<RandomProbabilisticSamplerOptions, RandomProbabilisticSamplerOptionsValidator>();
+        _ = builder.Services
+            .AddSingleton<IConfigureOptions<RandomProbabilisticSamplerOptions>>(
                 new RandomProbabilisticSamplerConfigureOptions(configuration));
+        _ = builder.Services
+            .AddSingleton<IOptionsChangeTokenSource<RandomProbabilisticSamplerOptions>>(
+                new ConfigurationChangeTokenSource<RandomProbabilisticSamplerOptions>(configuration));
 
-        _ = builder.Services.AddSingleton(typeof(LogSamplingRuleSelector<>));
+        _ = builder.Services
+            .AddSingleton(typeof(LogSamplingRuleSelector<>));
 
         return builder.AddSampler<RandomProbabilisticSampler>();
     }

test/Libraries/Microsoft.Extensions.Telemetry.Tests/Sampling/SamplingLoggerBuilderExtensionsTests.cs

@@ -9,6 +9,7 @@
 using Microsoft.Extensions.Diagnostics.Sampling;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Extensions.Logging.Test;
 using Microsoft.Extensions.Options;
 using Xunit;
 
@@ -72,6 +73,86 @@ public void AddRandomProbabilisticSamplerFromConfiguration_RegistersInDI()
         Assert.Equivalent(expectedData, options.CurrentValue.Rules);
     }
 
+    [Fact]
+    public void AddRandomProbabilisticSamplerFromConfig_PicksUpConfigChanges()
+    {
+        List<RandomProbabilisticSamplerFilterRule> initialData =
+        [
+            new(probability: 1.0, categoryName: "Program.MyLogger", logLevel: LogLevel.Information, eventId: 1, eventName: "number one"),
+            new(probability : 0.01, logLevel : LogLevel.Information),
+            new(probability : 0.1, logLevel : LogLevel.Warning)
+        ];
+        List<RandomProbabilisticSamplerFilterRule> updatedData =
+        [
+            new(probability: 0, logLevel: LogLevel.Information),
+            new(probability : 0, logLevel : LogLevel.Information),
+            new(probability : 0, logLevel : LogLevel.Warning)
+        ];
+        string jsonConfig =
+            @"
+{
+  ""RandomProbabilisticSampler"": {
+    ""Rules"": [
+      {
+        ""CategoryName"": ""Program.MyLogger"",
+        ""LogLevel"": ""Information"",
+        ""EventId"": 1,
+        ""EventName"": ""number one"",
+        ""Probability"": 1.0
+      },
+      {
+        ""LogLevel"": ""Information"",
+        ""Probability"": 0.01
+      },
+      {
+        ""LogLevel"": ""Warning"",
+        ""Probability"": 0.1
+      }
+    ]
+  }
+}
+";
+
+        using var config = TestConfiguration.Create(() => jsonConfig);
+        var serviceCollection = new ServiceCollection();
+        serviceCollection.AddLogging(builder =>
+        {
+            builder.AddRandomProbabilisticSampler(config);
+        });
+        ServiceProvider serviceProvider = serviceCollection.BuildServiceProvider();
+        IOptionsMonitor<RandomProbabilisticSamplerOptions>? options = serviceProvider.GetService<IOptionsMonitor<RandomProbabilisticSamplerOptions>>();
+        Assert.NotNull(options);
+        Assert.NotNull(options.CurrentValue);
+        Assert.Equivalent(initialData, options.CurrentValue.Rules);
+
+        jsonConfig =
+@"
+{
+  ""RandomProbabilisticSampler"": {
+    ""Rules"": [
+      {
+        ""LogLevel"": ""Information"",
+        ""Probability"": 0
+      },
+      {
+        ""LogLevel"": ""Information"",
+        ""Probability"": 0
+      },
+      {
+        ""LogLevel"": ""Warning"",
+        ""Probability"": 0
+      }
+    ]
+  }
+}
+";
+        config.Reload();
+
+        var sampler = serviceProvider.GetRequiredService<LoggingSampler>() as RandomProbabilisticSampler;
+        Assert.NotNull(sampler);
+        Assert.Equivalent(updatedData, sampler.LastKnownGoodSamplerRules);
+    }
+
     [Fact]
     public void AddRandomProbabilisticSampler_WhenRulesIsNull_ValidationFails()
     {