Method Fetch

core/remotes/docker/fetcher.go:221–330

(ctx context.Context, desc ocispec.Descriptor)

}

func (r dockerFetcher) Fetch(ctx context.Context, desc ocispec.Descriptor) (io.ReadCloser, error) {
	ctx = log.WithLogger(ctx, log.G(ctx).WithField("digest", desc.Digest))

	hosts := r.filterHosts(HostCapabilityPull)
	if len(hosts) == 0 {
		return nil, fmt.Errorf("no pull hosts: %w", errdefs.ErrNotFound)
	}

	ctx, err := ContextWithRepositoryScope(ctx, r.refspec, false)
	if err != nil {
		return nil, err
	}

	return newHTTPReadSeeker(desc.Size, func(offset int64) (io.ReadCloser, error) {
		// firstly try fetch via external urls
		for _, us := range desc.URLs {
			u, err := url.Parse(us)
			if err != nil {
				log.G(ctx).WithError(err).Debugf("failed to parse %q", us)
				continue
			}
			if u.Scheme != "http" && u.Scheme != "https" {
				log.G(ctx).Debug("non-http(s) alternative url is unsupported")
				continue
			}
			ctx = log.WithLogger(ctx, log.G(ctx).WithField("url", u))
			log.G(ctx).Info("request")

			// Try this first, parse it
			host := RegistryHost{
				Client:       http.DefaultClient,
				Host:         u.Host,
				Scheme:       u.Scheme,
				Path:         u.Path,
				Capabilities: HostCapabilityPull,
			}
			req := r.request(host, http.MethodGet)
			// Strip namespace from base
			req.path = u.Path
			if u.RawQuery != "" {
				req.path = req.path + "?" + u.RawQuery
			}

			rc, _, err := r.open(ctx, req, desc.MediaType, offset, false)
			if err != nil {
				if errdefs.IsNotFound(err) {
					continue // try one of the other urls.
				}

				return nil, err
			}

			return rc, nil
		}

		// Try manifests endpoints for manifests types
		if images.IsManifestType(desc.MediaType) || images.IsIndexType(desc.MediaType) {