Tracer flare - Inspect the AGENT_CONFIG content to set the log level (#5802)

## Summary of changes

When receiving the AGENT_CONFIG remote config, inspect the json to
extract the log level, instead of relying only on the filename.

## Reason for change

The filename is subject to change.

## Implementation details

In theory we should remove entirely the old behavior (checking the file
name) but the AGENT_CONFIG seems broken at the moment so I can't
properly test it. To play it safe, I just merged the new and old logic.

## Test coverage

Added a test case with a file name that doesn't contain the log level.

Author: Kevin Gosse

tracer/src/Datadog.Trace/Logging/TracerFlare/TracerFlareManager.cs

@@ -9,7 +9,6 @@
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Datadog.Trace.Agent.DiscoveryService;
@@ -34,6 +33,8 @@ internal class TracerFlareManager : ITracerFlareManager
     private readonly IRcmSubscriptionManager _subscriptionManager;
     private readonly ITelemetryController _telemetryController;
     private readonly TracerFlareApi _flareApi;
+
+    private string? _debugEnabledConfigPath;
     private ISubscription? _subscription;
     private Timer? _resetTimer = null;
 
@@ -86,6 +87,7 @@ private void ResetDebugging()
         // Restore the log level to its old value
         if (!_wasDebugLogEnabled)
         {
+            _debugEnabledConfigPath = null;
             GlobalSettings.SetDebugEnabledInternal(false);
         }
     }
@@ -126,9 +128,10 @@ private async Task<ApplyDetails[]> HandleTracerFlareInitiated(List<RemoteConfigu
             var debugRequested = false;
             foreach (var remoteConfig in config)
             {
-                if (IsEnableDebugConfig(remoteConfig.Path))
+                if (IsEnableDebugConfig(remoteConfig))
                 {
                     debugRequested = true;
+                    _debugEnabledConfigPath = remoteConfig.Path.Path;
                     break;
                 }
             }
@@ -180,12 +183,16 @@ private void HandleTracerFlareResolved(List<RemoteConfigurationPath> config)
         try
         {
             var enableDebugDeleted = false;
-            foreach (var removedConfig in config)
+
+            if (_debugEnabledConfigPath != null)
             {
-                if (IsEnableDebugConfig(removedConfig))
+                foreach (var removedConfig in config)
                 {
-                    enableDebugDeleted = true;
-                    break;
+                    if (_debugEnabledConfigPath == removedConfig.Path)
+                    {
+                        enableDebugDeleted = true;
+                        break;
+                    }
                 }
             }
 
@@ -341,10 +348,32 @@ static bool TryGetArg(JObject argsObject, string name, string configPath, [NotNu
         }
     }
 
-    private static bool IsEnableDebugConfig(RemoteConfigurationPath remoteConfigPath)
+    private static bool IsEnableDebugConfig(RemoteConfiguration remoteConfig)
     {
-        return remoteConfigPath.Id.Equals("flare-log-level.debug", StringComparison.Ordinal)
-            || remoteConfigPath.Id.Equals("flare-log-level.trace", StringComparison.Ordinal);
+        try
+        {
+            var remoteConfigPath = remoteConfig.Path;
+
+            if (remoteConfigPath.Id.Equals("flare-log-level.debug", StringComparison.Ordinal)
+                || remoteConfigPath.Id.Equals("flare-log-level.trace", StringComparison.Ordinal))
+            {
+                return true;
+            }
+
+            var json = JObject.Parse(EncodingHelpers.Utf8NoBom.GetString(remoteConfig.Contents));
+
+            var logLevel = json["config"]?["log_level"]?.Value<string>();
+
+            return logLevel is not null
+                && (logLevel.Equals("debug", StringComparison.OrdinalIgnoreCase)
+                    || logLevel.Equals("trace", StringComparison.OrdinalIgnoreCase));
+        }
+        catch (Exception ex)
+        {
+            Log.Error(ex, "Invalid configuration provided for tracer flare");
+        }
+
+        return false;
     }
 
     private static ApplyDetails[] AcknowledgeAll(List<RemoteConfiguration> config)

tracer/test/Datadog.Trace.ClrProfiler.IntegrationTests/TracerFlareTests.cs

@@ -5,7 +5,6 @@
 
 using System;
 using System.IO.Compression;
-using System.Linq;
 using System.Threading.Tasks;
 using Datadog.Trace.Configuration;
 using Datadog.Trace.Logging.TracerFlare;
@@ -34,9 +33,11 @@ public TracerFlareTests(ITestOutputHelper output)
         SetEnvironmentVariable(ConfigurationKeys.Rcm.PollInterval, "5");
     }
 
-    [SkippableFact]
+    [SkippableTheory]
+    [InlineData(true)]
+    [InlineData(false)]
     [Trait("RunOnWindows", "True")]
-    public async Task SendTracerFlare()
+    public async Task SendTracerFlare(bool logLevelInFileName)
     {
         using var agent = EnvironmentHelper.GetMockAgent(useTelemetry: true);
         var processName = EnvironmentHelper.IsCoreClr() ? "dotnet" : "Samples.Console";
@@ -47,7 +48,7 @@ public async Task SendTracerFlare()
         {
             _ = await logEntryWatcher.WaitForLogEntry(DiagnosticLog);
 
-            await InitializeFlare(agent, logEntryWatcher);
+            await InitializeFlare(agent, logEntryWatcher, logLevelInFileName);
             await TriggerFlareCollection(agent, logEntryWatcher);
         }
         finally
@@ -76,11 +77,23 @@ public async Task SendTracerFlare()
            .And.Contain(x => x.Name.StartsWith("dotnet-tracer-telemetry-"));
     }
 
-    private async Task InitializeFlare(MockTracerAgent agent, LogEntryWatcher logEntryWatcher)
+    private async Task InitializeFlare(MockTracerAgent agent, LogEntryWatcher logEntryWatcher, bool logLevelInFileName)
     {
-        var fileId = "flare-log-level.debug";
+        string fileId;
+        object payload;
 
-        var request = await agent.SetupRcmAndWait(Output, new[] { ((object)new { }, RcmProducts.TracerFlareInitiated, fileId) });
+        if (logLevelInFileName)
+        {
+            fileId = "flare-log-level.debug";
+            payload = new { };
+        }
+        else
+        {
+            fileId = Guid.NewGuid().ToString();
+            payload = new { config = new { log_level = "debug" } };
+        }
+
+        var request = await agent.SetupRcmAndWait(Output, new[] { (payload, RcmProducts.TracerFlareInitiated, fileId) });
 
         request.Should().NotBeNull();
         request.Client.State.ConfigStates.Should().ContainSingle(f => f.Id == fileId)