Parallelize signature fetch in signature store

To avoid compounded round trips leading to slow retrieval of manifests with a
large number of signatures, the fetch of signatures has been parallelized. This
simply spawns a goroutine for each path, coordinated with a sync.WaitGroup.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
This commit is contained in:
Stephen J Day 2015-04-06 19:10:50 -07:00
parent 0a2affa79f
commit 1eab4b79bc

View file

@ -2,8 +2,10 @@ package storage
import (
"path"
"sync"
"github.com/docker/distribution"
"github.com/docker/distribution/context"
"github.com/docker/distribution/digest"
)
@ -33,18 +35,42 @@ func (s *signatureStore) Get(dgst digest.Digest) ([][]byte, error) {
return nil, err
}
var signatures [][]byte
for _, sigPath := range signaturePaths {
var wg sync.WaitGroup
signatures := make([][]byte, len(signaturePaths)) // make space for everything
errCh := make(chan error, 1) // buffered chan so one proceeds
for i, sigPath := range signaturePaths {
// Append the link portion
sigPath = path.Join(sigPath, "link")
// TODO(stevvooe): These fetches should be parallelized for performance.
p, err := s.blobStore.linked(sigPath)
if err != nil {
return nil, err
}
wg.Add(1)
go func(idx int, sigPath string) {
defer wg.Done()
context.GetLogger(s.ctx).
Debugf("fetching signature from %q", sigPath)
p, err := s.blobStore.linked(sigPath)
if err != nil {
context.GetLogger(s.ctx).
Errorf("error fetching signature from %q: %v", sigPath, err)
signatures = append(signatures, p)
// try to send an error, if it hasn't already been sent.
select {
case errCh <- err:
default:
}
return
}
signatures[idx] = p
}(i, sigPath)
}
wg.Wait()
select {
case err := <-errCh:
// just return the first error, similar to single threaded code.
return nil, err
default:
// pass
}
return signatures, nil