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dockerutil.go
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dockerutil.go
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// Copyright 2017 GRAIL, Inc. All rights reserved.
// Use of this source code is governed by the Apache 2.0
// license that can be found in the LICENSE file.
package local
import (
"context"
"encoding/base64"
"encoding/json"
"io"
"sync"
"github.com/docker/distribution/reference"
"github.com/docker/docker/pkg/jsonmessage"
"github.com/docker/engine-api/client"
"github.com/docker/engine-api/types"
"github.com/grailbio/reflow/internal/ecrauth"
)
// imageExists checks whether an image exists at a Docker client.
func imageExists(ctx context.Context, client *client.Client, id string) (bool, error) {
ref, err := reference.Parse(id)
if err != nil {
return false, err
}
images, err := client.ImageList(ctx, types.ImageListOptions{})
if err != nil {
return false, err
}
var useDigest bool
switch r := ref.(type) {
case reference.Digested:
useDigest = true
case reference.Tagged:
// Do nothing; needed for excluding tagged images in below case.
case reference.Named:
// Does not have digest or tag.
ref, err = reference.WithTag(r, "latest")
if err != nil {
return false, err
}
}
refStr := ref.String()
for _, image := range images {
if useDigest {
for _, digest := range image.RepoDigests {
if digest == refStr {
return true, nil
}
}
} else {
for _, tag := range image.RepoTags {
if tag == refStr {
return true, nil
}
}
}
}
return false, nil
}
// pullImage pulls an image (by reference) to a Docker client using an authenticator.
func pullImage(ctx context.Context, client *client.Client, authenticator ecrauth.Interface, ref string) error {
var options types.ImagePullOptions
if authenticator != nil {
if ok, err := authenticator.Authenticates(ctx, ref); ok && err == nil {
var auth types.AuthConfig
if err := authenticator.Authenticate(ctx, &auth); err != nil {
return err
}
b, err := json.Marshal(auth)
if err != nil {
return err
}
options.RegistryAuth = base64.URLEncoding.EncodeToString(b)
} else if err != nil {
return err
}
}
resp, err := client.ImagePull(ctx, ref, options)
if err != nil {
return err
}
// TODO(marius): report progress up the chain.
defer resp.Close()
decoder := json.NewDecoder(resp)
// Docker sends status messages (e.g., "x% downloaded").
// We don't currently display these, but nonetheless have to
// consume them.
for {
var msg jsonmessage.JSONMessage
if err := decoder.Decode(&msg); err == io.EOF {
break
} else if err != nil {
return err
}
if msg.Error != nil {
return msg.Error
}
}
return nil
}
// image manages the status of a single image that is either pulled
// or in the process of being pulled. It is used to rendezvous
// multiple execs that are pulling a single image.
type image struct {
sync.Mutex
*sync.Cond
done bool
err error
}
var (
clientMu sync.Mutex
clientIm = map[*client.Client]map[string]*image{}
)
// ensureImage returns nil when the image is known to be present
// at the given Docker client. ensureImage ensures that there is only
// one concurrent pull per image, per client.
func ensureImage(ctx context.Context, client *client.Client, authenticator ecrauth.Interface, ref string) error {
clientMu.Lock()
images := clientIm[client]
if images == nil {
images = map[string]*image{}
clientIm[client] = images
}
im := images[ref]
if im != nil {
clientMu.Unlock()
im.Lock()
for !im.done {
im.Wait()
}
im.Unlock()
return im.err
}
im = &image{}
im.Cond = sync.NewCond(im)
images[ref] = im
clientMu.Unlock()
defer func() {
im.Lock()
im.done = true
im.Broadcast()
im.Unlock()
}()
if ok, _ := imageExists(ctx, client, ref); ok {
return nil
}
im.err = pullImage(ctx, client, authenticator, ref)
if im.err != nil {
// Let subsequent fetches retry.
clientMu.Lock()
delete(images, ref)
clientMu.Unlock()
}
return im.err
}