fix(server): memory leak in cache warmer (#4095)

* Prevent cache warmer memory leak when cache disabled

* refactor(tests): replace disabledCache with mockFileCache in CacheWarmer tests

Signed-off-by: Deluan <deluan@navidrome.org>

* test(cache): enhance CacheWarmer tests for initialization, buffer management, and error handling

Signed-off-by: Deluan <deluan@navidrome.org>

---------

Signed-off-by: Deluan <deluan@navidrome.org>

utils/cache/file_caches.go

@@ -54,6 +54,9 @@ type FileCache interface {
 
 	// Available checks if the cache is available
 	Available(ctx context.Context) bool
+
+	// Disabled reports if the cache has been permanently disabled
+	Disabled(ctx context.Context) bool
 }
 
 // NewFileCache creates a new FileCache. This function initializes the cache and starts it in the background.
@@ -119,6 +122,13 @@ func (fc *fileCache) Available(_ context.Context) bool {
 	return fc.ready.Load() && !fc.disabled
 }
 
+func (fc *fileCache) Disabled(_ context.Context) bool {
+	fc.mutex.RLock()
+	defer fc.mutex.RUnlock()
+
+	return fc.disabled
+}
+
 func (fc *fileCache) invalidate(ctx context.Context, key string) error {
 	if !fc.Available(ctx) {
 		log.Debug(ctx, "Cache not initialized yet. Cannot invalidate key", "cache", fc.name, "key", key)

utils/cache/file_caches_test.go

@@ -50,6 +50,13 @@ var _ = Describe("File Caches", func() {
 			Expect(fc.cache).To(BeNil())
 			Expect(fc.disabled).To(BeTrue())
 		})
+
+		It("reports when cache is disabled", func() {
+			fc := callNewFileCache("test", "0", "test", 0, nil)
+			Expect(fc.Disabled(context.Background())).To(BeTrue())
+			fc = callNewFileCache("test", "1KB", "test", 0, nil)
+			Expect(fc.Disabled(context.Background())).To(BeFalse())
+		})
 	})
 
 	Describe("FileCache", func() {