Add detailed logging for image requests with cache status and timing

internal/handlers/image.go

@@ -78,7 +78,11 @@ func (s *Handlers) HandleImage() http.HandlerFunc {
 			return
 		}
 
+		// Get cache key for logging
+		cacheKey := imgcache.CacheKey(req)
+
 		// Get the image (from cache or fetch/process)
+		startTime := time.Now()
 		resp, err := s.imgSvc.Get(ctx, req)
 		if err != nil {
 			s.log.Error("failed to get image",
@@ -120,6 +124,17 @@ func (s *Handlers) HandleImage() http.HandlerFunc {
 			w.Header().Set("ETag", resp.ETag)
 		}
 
+		// Log cache status and timing
+		duration := time.Since(startTime)
+		s.log.Info("image served",
+			"cache_key", cacheKey,
+			"cache_status", resp.CacheStatus,
+			"duration_ms", duration.Milliseconds(),
+			"format", req.Format,
+			"served_bytes", resp.ContentLength,
+			"fetched_bytes", resp.FetchedBytes,
+		)
+
 		// Stream the response
 		w.WriteHeader(http.StatusOK)
 

internal/imgcache/imgcache.go

@@ -90,6 +90,8 @@ type ImageResponse struct {
 	LastModified time.Time
 	// CacheStatus indicates HIT, MISS, or STALE
 	CacheStatus CacheStatus
+	// FetchedBytes is the number of bytes fetched from upstream (0 if cache hit)
+	FetchedBytes int64
 }
 
 // CacheStatus indicates whether the response was served from cache.

internal/imgcache/service.go

@@ -172,6 +172,7 @@ func (s *Service) fetchAndProcess(ctx context.Context, req *ImageRequest) (*Imag
 		Content:       io.NopCloser(bytes.NewReader(processedData)),
 		ContentLength: int64(len(processedData)),
 		ContentType:   processResult.ContentType,
+		FetchedBytes:  int64(len(sourceData)),
 	}, nil
 }