Method ServeHTTP

pkg/server/image.go:339–428

(rw http.ResponseWriter, req *http.Request, file blob.Ref)

var singleResize singleflight.Group

func (ih *ImageHandler) ServeHTTP(rw http.ResponseWriter, req *http.Request, file blob.Ref) {
	ctx := req.Context()
	if !httputil.IsGet(req) {
		http.Error(rw, "Invalid method", http.StatusBadRequest)
		return
	}
	mw, mh := ih.MaxWidth, ih.MaxHeight
	if mw == 0 || mh == 0 || mw > search.MaxImageSize || mh > search.MaxImageSize {
		http.Error(rw, "bogus dimensions", http.StatusBadRequest)
		return
	}

	key := cacheKey(file.String(), mw, mh)
	etag := blob.RefFromString(key).String()[5:]
	inm := req.Header.Get("If-None-Match")
	if inm != "" {
		if strings.Trim(inm, `"`) == etag {
			thumbCacheHeader304.Add(1)
			rw.WriteHeader(http.StatusNotModified)
			return
		}
	} else {
		if !disableThumbCache && req.Header.Get("If-Modified-Since") != "" {
			thumbCacheHeader304.Add(1)
			rw.WriteHeader(http.StatusNotModified)
			return
		}
	}

	var imageData []byte
	format := ""
	cacheHit := false
	if ih.ThumbMeta != nil && !disableThumbCache {
		var buf bytes.Buffer
		format = ih.scaledCached(ctx, &buf, file)
		if format != "" {
			cacheHit = true
			imageData = buf.Bytes()
		}
	}

	if !cacheHit {
		thumbCacheMiss.Add(1)
		imi, err := singleResize.Do(key, func() (interface{}, error) {
			return ih.scaleImage(ctx, file)
		})
		if err != nil {
			http.Error(rw, err.Error(), 500)
			return
		}
		im := imi.(*formatAndImage)
		imageData = im.image
		format = im.format
		if ih.ThumbMeta != nil {
			err := ih.cacheScaled(ctx, imageData, key)
			if err != nil {
				log.Printf("image resize: %v", err)
			}