func (s *TagStore) pushImageToEndpoint(endpoint string, out io.Writer, remoteName string, imageIDs []string, tags map[string][]string, repo *registry.RepositoryData, sf *streamformatter.StreamFormatter, r *registry.Session) error { workerCount := len(imageIDs) // start a maximum of 5 workers to check if images exist on the specified endpoint. if workerCount > 5 { workerCount = 5 } var ( wg = &sync.WaitGroup{} imageData = make(chan imagePushData, workerCount*2) imagesToPush = make(chan string, workerCount*2) pushes = make(chan map[string]struct{}, 1) ) for i := 0; i < workerCount; i++ { wg.Add(1) go lookupImageOnEndpoint(wg, r, out, sf, imageData, imagesToPush) } // start a go routine that consumes the images to push go func() { shouldPush := make(map[string]struct{}) for id := range imagesToPush { shouldPush[id] = struct{}{} } pushes <- shouldPush }() for _, id := range imageIDs { imageData <- imagePushData{ id: id, endpoint: endpoint, tokens: repo.Tokens, } } // close the channel to notify the workers that there will be no more images to check. close(imageData) wg.Wait() close(imagesToPush) // wait for all the images that require pushes to be collected into a consumable map. shouldPush := <-pushes // finish by pushing any images and tags to the endpoint. The order that the images are pushed // is very important that is why we are still iterating over the ordered list of imageIDs. for _, id := range imageIDs { if _, push := shouldPush[id]; push { if _, err := s.pushImage(r, out, id, endpoint, repo.Tokens, sf); err != nil { // FIXME: Continue on error? return err } } for _, tag := range tags[id] { out.Write(sf.FormatStatus("", "Pushing tag for rev [%s] on {%s}", stringid.TruncateID(id), endpoint+"repositories/"+remoteName+"/tags/"+tag)) if err := r.PushRegistryTag(remoteName, id, tag, endpoint); err != nil { return err } } } return nil }