fix: resolve repeated read panic by pinning connection in goroutines

WORKLOG.md

@@ -0,0 +1,27 @@
+# MusicLink Worklog
+
+## 2026-01-20
+
+### Current Status
+- **Backend:** Go (v1.22.8) bot using Matterbridge WebSocket API.
+- **Deployment:** NixOS based (flake.nix), currently managed on `ops-jrz1`.
+- **Issues:**
+    1. **Crash Loop:** `musiclink.service` is failing with `panic: repeated read on failed websocket connection`.
+    2. **API Instability:** `idonthavespotify` API reported to be returning 500s.
+    3. **Environment:** `matterbridge.service` not found on local system (likely running elsewhere or under a different name).
+
+### Actions Taken
+1. **Investigation:**
+    - Verified `musiclink.service` status and read `bot-crash.log`.
+    - Confirmed the panic location in `internal/bot/bot.go:186`.
+    - Verified `idonthavespotify` API status: **Currently responsive (200 OK)** for specific Spotify album links. Intermittent 500s may still occur.
+    - Tested Odesli (song.link) API as a potential fallback.
+2. **Analysis:**
+    - Identified that `readLoop` in `bot.go` needs to handle connection closures more gracefully to avoid the "repeated read" panic.
+    - Verified that secrets (Matterbridge token) are handled via `sops-nix` by the platform team.
+
+### Next Steps
+- Implement fix for WebSocket panic in `internal/bot/bot.go`.
+- Finalize investigation into `idonthavespotify` 500 errors.
+- If 500s persist, implement Odesli (song.link) as an alternative service provider.
+- Coordinate with platform team regarding `matterbridge` service status.

internal/bot/bot.go

@@ -126,6 +126,14 @@ func (b *Bot) Run(ctx context.Context) error {
 
 // runLoop processes messages until the connection is lost or context is canceled.
 func (b *Bot) runLoop(ctx context.Context) error {
+	b.mu.Lock()
+	conn := b.conn
+	b.mu.Unlock()
+
+	if conn == nil {
+		return fmt.Errorf("connection is nil")
+	}
+
 	// Create a sub-context for this specific connection's goroutines
 	connCtx, cancel := context.WithCancel(ctx)
 	defer cancel()
@@ -135,11 +143,11 @@ func (b *Bot) runLoop(ctx context.Context) error {
 
 	// Start reader goroutine
 	go func() {
-		readDone <- b.readLoop(connCtx)
+		readDone <- b.readLoop(connCtx, conn)
 	}()
 
 	// Start ping goroutine
-	go b.pingLoop(connCtx)
+	go b.pingLoop(connCtx, conn)
 
 	// Process messages
 	for {
@@ -171,7 +179,7 @@ func (b *Bot) runLoop(ctx context.Context) error {
 }
 
 // readLoop reads messages from the WebSocket connection.
-func (b *Bot) readLoop(ctx context.Context) error {
+func (b *Bot) readLoop(ctx context.Context, conn *websocket.Conn) error {
 	for {
 		select {
 		case <-ctx.Done():
@@ -179,14 +187,6 @@ func (b *Bot) readLoop(ctx context.Context) error {
 		default:
 		}
 
-		b.mu.Lock()
-		conn := b.conn
-		b.mu.Unlock()
-
-		if conn == nil {
-			return fmt.Errorf("connection is nil")
-		}
-
 		_, data, err := conn.ReadMessage()
 		if err != nil {
 			if websocket.IsCloseError(err, websocket.CloseNormalClosure) {
@@ -212,7 +212,7 @@ func (b *Bot) readLoop(ctx context.Context) error {
 }
 
 // pingLoop sends periodic pings to keep the connection alive.
-func (b *Bot) pingLoop(ctx context.Context) {
+func (b *Bot) pingLoop(ctx context.Context, conn *websocket.Conn) {
 	ticker := time.NewTicker(30 * time.Second)
 	defer ticker.Stop()
 
@@ -221,14 +221,6 @@ func (b *Bot) pingLoop(ctx context.Context) {
 		case <-ctx.Done():
 			return
 		case <-ticker.C:
-			b.mu.Lock()
-			conn := b.conn
-			b.mu.Unlock()
-
-			if conn == nil {
-				return
-			}
-
 			conn.SetWriteDeadline(time.Now().Add(5 * time.Second))
 			if err := conn.WriteMessage(websocket.PingMessage, nil); err != nil {
 				log.Printf("Ping failed: %v", err)