fix: include ffmpeg exit diagnostics

src/LiveRecorder.Infrastructure/Services/FfmpegService.Runtime.cs

@@ -28,6 +28,7 @@ public sealed partial class FfmpegService
             return;
         }
 
+        runtime.RememberOutputLine(line, isError);
         _logger.LogDebug("ffmpeg[{SessionId}] {Line}", runtime.RecordSessionId, line);
         if (TryParseSegmentOpenPath(line, out var openedPath))
         {
@@ -921,9 +922,7 @@ public sealed partial class FfmpegService
             SystemLogLevel.Error,
             "FFmpeg",
             $"Recording session exited with status={session.Status}.",
-            toleratedNonZeroExit
-                ? $"exitCode={process.ExitCode}; output={effectiveOutputPath}; recorderOutput={runtime.RecorderOutputPath}; non-zero exit was tolerated because completion was requested and the output is usable"
-                : $"exitCode={process.ExitCode}; output={effectiveOutputPath}; recorderOutput={runtime.RecorderOutputPath}",
+            BuildExitLogDetail(runtime, process.ExitCode, effectiveOutputPath, toleratedNonZeroExit, finalizationError),
             session.LiveRoomId,
             session.Id,
             currentTask.Id);
@@ -935,21 +934,60 @@ public sealed partial class FfmpegService
 
         if (session.Status == RecordSessionStatus.Failed && session.LiveRoom is not null)
         {
+            var failureDetail = BuildExitLogDetail(runtime, process.ExitCode, effectiveOutputPath, toleratedNonZeroExit: false, finalizationError);
             await emailNotificationService.SendExceptionAsync(
                 "FFmpeg",
                 "Recording session exited abnormally.",
-                $"exitCode={process.ExitCode}; output={effectiveOutputPath}",
+                failureDetail,
                 session.LiveRoom,
                 currentTask);
             await webhookNotificationService.SendExceptionAsync(
                 "FFmpeg",
                 "Recording session exited abnormally.",
-                $"exitCode={process.ExitCode}; output={effectiveOutputPath}",
+                failureDetail,
                 session.LiveRoom,
                 currentTask);
         }
     }
 
+    private static string BuildExitLogDetail(
+        SessionProcessRuntime runtime,
+        int exitCode,
+        string? effectiveOutputPath,
+        bool toleratedNonZeroExit,
+        string? finalizationError)
+    {
+        var parts = new List<string>
+        {
+            $"exitCode={exitCode}",
+            $"output={effectiveOutputPath}",
+            $"recorderOutput={runtime.RecorderOutputPath}"
+        };
+
+        if (toleratedNonZeroExit)
+        {
+            parts.Add("non-zero exit was tolerated because completion was requested and the output is usable");
+        }
+
+        if (!string.IsNullOrWhiteSpace(finalizationError))
+        {
+            parts.Add($"finalizationError={finalizationError}");
+        }
+
+        if (!string.IsNullOrWhiteSpace(runtime.LastStartupFailureLine))
+        {
+            parts.Add($"startupFailure={runtime.LastStartupFailureLine}");
+        }
+
+        var recentOutput = runtime.GetRecentOutputSummary();
+        if (!string.IsNullOrWhiteSpace(recentOutput))
+        {
+            parts.Add($"recentOutput={recentOutput}");
+        }
+
+        return string.Join("; ", parts);
+    }
+
     private async Task FinalizeCompletedSegmentAsync(
         Guid recordSessionId,
         Guid recordTaskId,
@@ -1566,6 +1604,8 @@ public sealed partial class FfmpegService
         public Task? DanmakuPumpTask { get; set; }
         private List<string> CurrentRecorderSegmentPaths { get; } = [];
         private object RuntimeSourceFailureSync { get; } = new();
+        private object RecentOutputSync { get; } = new();
+        private Queue<string> RecentOutputLines { get; } = new();
         private DateTimeOffset RuntimeSourceFailureWindowStartedAt { get; set; }
         private int RuntimeSourceFailureCount { get; set; }
         private bool RuntimeSourceFailureVerificationInProgress { get; set; }
@@ -1600,6 +1640,28 @@ public sealed partial class FfmpegService
 
         public void MarkForceKilled() => WasForceKilled = true;
 
+        public void RememberOutputLine(string line, bool isError)
+        {
+            lock (RecentOutputSync)
+            {
+                RecentOutputLines.Enqueue($"{(isError ? "stderr" : "stdout")}={line.Trim()}");
+                while (RecentOutputLines.Count > 8)
+                {
+                    RecentOutputLines.Dequeue();
+                }
+            }
+        }
+
+        public string? GetRecentOutputSummary()
+        {
+            lock (RecentOutputSync)
+            {
+                return RecentOutputLines.Count == 0
+                    ? null
+                    : string.Join(" | ", RecentOutputLines);
+            }
+        }
+
         public void ResetCurrentRecorderSegmentPaths(string openedPath)
         {
             CurrentRecorderSegmentPaths.Clear();