vbatts/registry
1
0
Fork 0
Code Issues Pull requests Releases Wiki Activity

Avoid stat round-trips when fetching a blob

Browse source 
Without this commit, three round-trips are required to fetch a blob with
a progress bar. The first is a call to Stat (HEAD request), to determine
the size. Then Open is called, which also calls Stat, and finally
performs a GET request.

Only the GET request is actually needed. The size of the blob can be
sniffed from Content-Length in the GET response.

This commit changes HTTPReadSeeker to automatically detect the size from
Content-Length instead of requiring it to be passed in. The Stat call is
removed from Open because it is no longer necessary.

HTTPReadSeeker now takes an additional errorHandler callback argument which
translates an unsuccessful HTTP response into an appropriate API-level
error. Using a callback for this makes it possible to avoid leaking the
repsonse body to Read's caller, which would make lifecycle management
problematic.

Fixes #1223

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
This commit is contained in:
Aaron Lehmann 2015-11-30 18:35:19 -08:00
parent c0d094a72a
commit bf2cc0a9d6
2 changed files with 65 additions and 34 deletions
Download patch file Download diff file Expand all files Collapse all files

15
docs/client/repository.go
View file

@ -391,17 +391,18 @@ func (bs *blobs) Get(ctx context.Context, dgst digest.Digest) ([]byte, error) {
}
func (bs *blobs) Open(ctx context.Context, dgst digest.Digest) (distribution.ReadSeekCloser, error) {
stat, err := bs.statter.Stat(ctx, dgst)
blobURL, err := bs.ub.BuildBlobURL(bs.name, dgst)
if err != nil {
return nil, err
}
blobURL, err := bs.ub.BuildBlobURL(bs.name, stat.Digest)
if err != nil {
return nil, err
}
return transport.NewHTTPReadSeeker(bs.client, blobURL, stat.Size), nil
return transport.NewHTTPReadSeeker(bs.client, blobURL,
func(resp *http.Response) error {
if resp.StatusCode == http.StatusNotFound {
return distribution.ErrBlobUnknown
}
return handleErrorResponse(resp)
}), nil
}
func (bs *blobs) ServeBlob(ctx context.Context, w http.ResponseWriter, r *http.Request, dgst digest.Digest) error {