perf: in-memory feed cache — load once at startup, append on upload, zero disk reads

app.py

@@ -355,7 +355,9 @@ def create(
                         f.write(thumb_bytes)
                     has_thumb = True
 
-                # Save metadata
+                # Save metadata to bucket (durability) + memory (instant reads)
+                audio_url = f"{BUCKET_URL}/songs/{song_id}/{wav_name}"
+                thumb_url = f"{BUCKET_URL}/songs/{song_id}/thumb.png" if has_thumb else None
                 meta = {
                     "id": song_id,
                     "title": title,
@@ -363,15 +365,19 @@ def create(
                     "tags": tags,
                     "lyrics": lyrics,
                     "duration": audio_duration,
+                    "audio_url": audio_url,
+                    "thumb_url": thumb_url,
                     "has_thumb": has_thumb,
                     "created_at": datetime.now(timezone.utc).isoformat(),
                 }
                 with open(f"{song_dir}/meta.json", "w") as f:
                     json.dump(meta, f, indent=2)
 
-                result["community_url"] = f"{BUCKET_URL}/songs/{song_id}/{wav_name}"
-                print(f"[create] Shared to community: {result['community_url']}")
-                _invalidate_feed()
+                # Prepend to in-memory feed (no re-scan needed)
+                _feed_songs.insert(0, meta)
+
+                result["community_url"] = audio_url
+                print(f"[create] Shared to community: {audio_url}")
             except Exception as upload_err:
                 print(f"[create] Community upload failed: {upload_err}")
 
@@ -406,43 +412,37 @@ def generate(
         raise
 
 
-# ── API: Community feed (cached) ──────────────────────────────────────────────
-import time as _time
-_feed_cache = {"data": "[]", "ts": 0}
-_FEED_TTL = 10  # seconds
+# ── Community feed (in-memory, loaded once at startup) ───────────────────────
+_feed_songs = []
 
-def _rebuild_feed() -> str:
-    songs = []
+def _load_feed_from_disk():
+    """One-time scan at startup to populate memory from bucket."""
     songs_dir = "/data/songs"
-    if os.path.isdir(songs_dir):
-        for song_id in os.listdir(songs_dir):
-            meta_path = os.path.join(songs_dir, song_id, "meta.json")
-            if os.path.isfile(meta_path):
-                try:
-                    with open(meta_path) as f:
-                        meta = json.load(f)
-                    meta["audio_url"] = f"{BUCKET_URL}/songs/{song_id}/{song_id}.wav"
-                    thumb_path = os.path.join(songs_dir, song_id, "thumb.png")
-                    if os.path.isfile(thumb_path):
-                        meta["thumb_url"] = f"{BUCKET_URL}/songs/{song_id}/thumb.png"
-                    songs.append(meta)
-                except Exception:
-                    pass
-    songs.sort(key=lambda s: s.get("created_at", ""), reverse=True)
-    return json.dumps(songs[:32])
-
-def _invalidate_feed():
-    """Call after uploading a new song to bust the cache."""
-    _feed_cache["ts"] = 0
+    if not os.path.isdir(songs_dir):
+        print("[feed] /data/songs not found, starting with empty feed")
+        return
+    for song_id in os.listdir(songs_dir):
+        meta_path = os.path.join(songs_dir, song_id, "meta.json")
+        if os.path.isfile(meta_path):
+            try:
+                with open(meta_path) as f:
+                    meta = json.load(f)
+                meta["audio_url"] = f"{BUCKET_URL}/songs/{song_id}/{song_id}.wav"
+                thumb_path = os.path.join(songs_dir, song_id, "thumb.png")
+                if os.path.isfile(thumb_path):
+                    meta["thumb_url"] = f"{BUCKET_URL}/songs/{song_id}/thumb.png"
+                _feed_songs.append(meta)
+            except Exception:
+                pass
+    _feed_songs.sort(key=lambda s: s.get("created_at", ""), reverse=True)
+    print(f"[feed] Loaded {len(_feed_songs)} songs into memory")
+
+_load_feed_from_disk()
 
 @app.api(name="community", concurrency_limit=4)
 def community() -> str:
-    """List community songs from the bucket. Cached for 10s."""
-    now = _time.monotonic()
-    if now - _feed_cache["ts"] > _FEED_TTL:
-        _feed_cache["data"] = _rebuild_feed()
-        _feed_cache["ts"] = now
-    return _feed_cache["data"]
+    """List community songs — served from memory, zero disk I/O."""
+    return json.dumps(_feed_songs[:50])
 
 
 # ── Serve custom HTML frontend ────────────────────────────────────────────────