Method writeNode

internal/dump/common.go:115–163

(ctx context.Context, w io.Writer, node *data.Node)

}

func (d *Dumper) writeNode(ctx context.Context, w io.Writer, node *data.Node) error {
	wg, ctx := errgroup.WithContext(ctx)
	limit := int(d.repo.Connections())
	wg.SetLimit(1 + limit) // +1 for the writer.
	blobs := make(chan (<-chan []byte), limit)

	// Writer.
	wg.Go(func() error {
		for ch := range blobs {
			select {
			case <-ctx.Done():
				return ctx.Err()
			case blob := <-ch:
				if _, err := w.Write(blob); err != nil {
					return err
				}
			}
		}
		return nil
	})

	// Start short-lived goroutines to load blobs.
loop:
	for _, id := range node.Content {
		// This needs to be buffered, so that loaders can quit
		// without waiting for the writer.
		ch := make(chan []byte, 1)

		wg.Go(func() error {
			blob, err := d.cache.GetOrCompute(id, func() ([]byte, error) {
				return d.repo.LoadBlob(ctx, restic.DataBlob, id, nil)
			})

			if err == nil {
				ch <- blob
			}
			return err
		})

		select {
		case blobs <- ch:
		case <-ctx.Done():
			break loop
		}
	}

	close(blobs)
	return wg.Wait()
}