feat: add metrics, observability, test fixtures, and scaling playbook artifacts

backend/playout/src/playlist.go

@@ -28,6 +28,9 @@ type VideoFile struct {
 
 var (
 	r2Client      *s3.Client
+	putObject     = func(client *s3.Client, input *s3.PutObjectInput) (*s3.PutObjectOutput, error) {
+		return client.PutObject(context.TODO(), input)
+	}
 	bucket        = os.Getenv("R2_BUCKET_NAME")
 	playoutMode   = "starting" // "live", "slate", "degraded"
 	restartCount  = 0
@@ -39,6 +42,9 @@ var (
 const (
 	maxRestartsPerMinute = 5
 	slateManifestName    = "playlist.m3u8"
+	// Cache-Control header values for R2 uploads.
+	segmentCacheControl = "public, max-age=31536000, immutable"
+	manifestCacheControl = "public, max-age=2"
 )
 
 // initR2Client initializes the R2 (S3-compatible) client
@@ -203,7 +209,7 @@ func validateKeyframeInterval(videoPath string) error {
 		"-v", "quiet",
 		"-select_streams", "v:0",
 		"-show_frames",
-		"-show_entries", "frame=key_frame,pkt_pts_time",
+		"-show_entries", "frame=key_frame,best_effort_timestamp_time,pkt_pts_time",
 		"-of", "csv=p=0",
 		videoPath)
 	output, err := cmd.Output()
@@ -223,8 +229,16 @@ func validateKeyframeInterval(videoPath string) error {
 		if len(parts) < 2 || parts[0] != "1" {
 			continue
 		}
-		pts, err := strconv.ParseFloat(strings.TrimSpace(parts[1]), 64)
-		if err != nil {
+		var pts float64
+		var found bool
+		for _, raw := range parts[1:] {
+			if value, err := strconv.ParseFloat(strings.TrimSpace(raw), 64); err == nil {
+				pts = value
+				found = true
+				break
+			}
+		}
+		if !found {
 			continue
 		}
 		keyframes = append(keyframes, kfEntry{pts})
@@ -284,7 +298,11 @@ func ValidatePlaylist(playlistPath string) ([]VideoFile, error) {
 	return videos, nil
 }
 
-// SyncToR2 uploads a file to R2 and returns the key
+// SyncToR2 uploads a file to R2 and returns the key.
+// Cache-Control is set automatically based on file extension:
+//   - .m4s, .ts, .mp4, .m4a  -> immutable (1 year)
+//   - .m3u8                   -> short-lived (2s, live manifest)
+//   - everything else          -> no cache header
 func SyncToR2(localPath, r2Key string) error {
 	if r2Client == nil {
 		if err := initR2Client(); err != nil {
@@ -298,11 +316,23 @@ func SyncToR2(localPath, r2Key string) error {
 	}
 	defer file.Close()
 
-	_, err = r2Client.PutObject(context.TODO(), &s3.PutObjectInput{
+	input := &s3.PutObjectInput{
 		Bucket: aws.String(bucket),
 		Key:    aws.String(r2Key),
 		Body:   file,
-	})
+	}
+
+	ext := strings.ToLower(filepath.Ext(r2Key))
+	switch ext {
+	case ".m4s", ".ts", ".mp4", ".m4a":
+		input.CacheControl = aws.String(segmentCacheControl)
+		input.ContentType = aws.String("video/MP2T")
+	case ".m3u8":
+		input.CacheControl = aws.String(manifestCacheControl)
+		input.ContentType = aws.String("application/vnd.apple.mpegurl")
+	}
+
+	_, err = putObject(r2Client, input)
 	return err
 }