Add simple cache warmer, disabled by default

core/cache_warmer.go

@@ -0,0 +1,72 @@
+package core
+
+import (
+	"context"
+	"io/ioutil"
+
+	"github.com/deluan/navidrome/conf"
+	"github.com/deluan/navidrome/core/pool"
+	"github.com/deluan/navidrome/log"
+)
+
+type CacheWarmer interface {
+	AddAlbum(ctx context.Context, albumID string)
+	Flush(ctx context.Context)
+}
+
+func NewCacheWarmer(cache ArtworkCache, artwork Artwork) CacheWarmer {
+	w := &warmer{
+		artwork: artwork,
+		cache:   cache,
+		albums:  map[string]struct{}{},
+	}
+	p, err := pool.NewPool("artwork", 3, &artworkItem{}, w.execute)
+	if err != nil {
+		log.Error(context.Background(), "Error creating pool for Album Artwork Cache Warmer", err)
+	} else {
+		w.pool = p
+	}
+
+	return w
+}
+
+type warmer struct {
+	pool    *pool.Pool
+	artwork Artwork
+	cache   ArtworkCache
+	albums  map[string]struct{}
+}
+
+func (w *warmer) AddAlbum(ctx context.Context, albumID string) {
+	if albumID == "" {
+		return
+	}
+	w.albums[albumID] = struct{}{}
+}
+
+func (w *warmer) Flush(ctx context.Context) {
+	if conf.Server.DevPreCacheAlbumArtwork {
+		if w.pool == nil || len(w.albums) == 0 {
+			return
+		}
+		log.Info(ctx, "Pre-caching album artworks", "numAlbums", len(w.albums))
+		for id := range w.albums {
+			w.pool.Submit(artworkItem{albumID: id})
+		}
+	}
+	w.albums = map[string]struct{}{}
+}
+
+func (w *warmer) execute(workload interface{}) {
+	ctx := context.Background()
+	item := workload.(artworkItem)
+	log.Trace(ctx, "Pre-caching album artwork", "albumID", item.albumID)
+	err := w.artwork.Get(ctx, item.albumID, 0, ioutil.Discard)
+	if err != nil {
+		log.Warn("Error pre-caching artwork from album", "id", item.albumID, err)
+	}
+}
+
+type artworkItem struct {
+	albumID string
+}