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pull.go
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pull.go
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package distribution
import (
"fmt"
"os"
"strings"
"github.com/Sirupsen/logrus"
"github.com/docker/docker/api"
"github.com/docker/docker/distribution/metadata"
"github.com/docker/docker/distribution/xfer"
"github.com/docker/docker/image"
"github.com/docker/docker/pkg/progress"
"github.com/docker/docker/reference"
"github.com/docker/docker/registry"
"github.com/docker/engine-api/types"
"golang.org/x/net/context"
)
// ImagePullConfig stores pull configuration.
type ImagePullConfig struct {
// MetaHeaders stores HTTP headers with metadata about the image
// (DockerHeaders with prefix X-Meta- in the request).
MetaHeaders map[string][]string
// AuthConfig holds authentication credentials for authenticating with
// the registry.
AuthConfig *types.AuthConfig
// ProgressOutput is the interface for showing the status of the pull
// operation.
ProgressOutput progress.Output
// RegistryService is the registry service to use for TLS configuration
// and endpoint lookup.
RegistryService *registry.Service
// ImageEventLogger notifies events for a given image
ImageEventLogger func(id, name, action string)
// MetadataStore is the storage backend for distribution-specific
// metadata.
MetadataStore metadata.Store
// ImageStore manages images.
ImageStore image.Store
// ReferenceStore manages tags.
ReferenceStore reference.Store
// DownloadManager manages concurrent pulls.
DownloadManager *xfer.LayerDownloadManager
}
// Puller is an interface that abstracts pulling for different API versions.
type Puller interface {
// Pull tries to pull the image referenced by `tag`
// Pull returns an error if any, as well as a boolean that determines whether to retry Pull on the next configured endpoint.
//
Pull(ctx context.Context, ref reference.Named) error
}
// newPuller returns a Puller interface that will pull from either a v1 or v2
// registry. The endpoint argument contains a Version field that determines
// whether a v1 or v2 puller will be created. The other parameters are passed
// through to the underlying puller implementation for use during the actual
// pull operation.
func newPuller(endpoint registry.APIEndpoint, repoInfo *registry.RepositoryInfo, imagePullConfig *ImagePullConfig) (Puller, error) {
switch endpoint.Version {
case registry.APIVersion2:
return &v2Puller{
blobSumService: metadata.NewBlobSumService(imagePullConfig.MetadataStore),
endpoint: endpoint,
config: imagePullConfig,
repoInfo: repoInfo,
}, nil
case registry.APIVersion1:
return &v1Puller{
v1IDService: metadata.NewV1IDService(imagePullConfig.MetadataStore),
endpoint: endpoint,
config: imagePullConfig,
repoInfo: repoInfo,
}, nil
}
return nil, fmt.Errorf("unknown version %d for registry %s", endpoint.Version, endpoint.URL)
}
// Pull initiates a pull operation. image is the repository name to pull, and
// tag may be either empty, or indicate a specific tag to pull.
func Pull(ctx context.Context, ref reference.Named, imagePullConfig *ImagePullConfig) error {
// Resolve the Repository name from fqn to RepositoryInfo
repoInfo, err := imagePullConfig.RegistryService.ResolveRepository(ref)
if err != nil {
return err
}
// makes sure name is not empty or `scratch`
if err := validateRepoName(repoInfo.Name()); err != nil {
return err
}
endpoints, err := imagePullConfig.RegistryService.LookupPullEndpoints(repoInfo)
if err != nil {
return err
}
var (
// use a slice to append the error strings and return a joined string to caller
errors []string
// discardNoSupportErrors is used to track whether an endpoint encountered an error of type registry.ErrNoSupport
// By default it is false, which means that if a ErrNoSupport error is encountered, it will be saved in errors.
// As soon as another kind of error is encountered, discardNoSupportErrors is set to true, avoiding the saving of
// any subsequent ErrNoSupport errors in errors.
// It's needed for pull-by-digest on v1 endpoints: if there are only v1 endpoints configured, the error should be
// returned and displayed, but if there was a v2 endpoint which supports pull-by-digest, then the last relevant
// error is the ones from v2 endpoints not v1.
discardNoSupportErrors bool
// confirmedV2 is set to true if a pull attempt managed to
// confirm that it was talking to a v2 registry. This will
// prevent fallback to the v1 protocol.
confirmedV2 bool
)
for _, endpoint := range endpoints {
if confirmedV2 && endpoint.Version == registry.APIVersion1 {
logrus.Debugf("Skipping v1 endpoint %s because v2 registry was detected", endpoint.URL)
continue
}
logrus.Debugf("Trying to pull %s from %s %s", repoInfo.Name(), endpoint.URL, endpoint.Version)
puller, err := newPuller(endpoint, repoInfo, imagePullConfig)
if err != nil {
errors = append(errors, err.Error())
continue
}
if err := puller.Pull(ctx, ref); err != nil {
// Was this pull cancelled? If so, don't try to fall
// back.
fallback := false
select {
case <-ctx.Done():
default:
if fallbackErr, ok := err.(fallbackError); ok {
fallback = true
confirmedV2 = confirmedV2 || fallbackErr.confirmedV2
err = fallbackErr.err
}
}
if fallback {
if _, ok := err.(registry.ErrNoSupport); !ok {
// Because we found an error that's not ErrNoSupport, discard all subsequent ErrNoSupport errors.
discardNoSupportErrors = true
// append subsequent errors
errors = append(errors, err.Error())
} else if !discardNoSupportErrors {
// Save the ErrNoSupport error, because it's either the first error or all encountered errors
// were also ErrNoSupport errors.
// append subsequent errors
errors = append(errors, err.Error())
}
continue
}
errors = append(errors, err.Error())
logrus.Debugf("Not continuing with error: %v", fmt.Errorf(strings.Join(errors, "\n")))
if len(errors) > 0 {
return fmt.Errorf(strings.Join(errors, "\n"))
}
}
imagePullConfig.ImageEventLogger(ref.String(), repoInfo.Name(), "pull")
return nil
}
if len(errors) == 0 {
return fmt.Errorf("no endpoints found for %s", ref.String())
}
if len(errors) > 0 {
return fmt.Errorf(strings.Join(errors, "\n"))
}
return nil
}
// writeStatus writes a status message to out. If layersDownloaded is true, the
// status message indicates that a newer image was downloaded. Otherwise, it
// indicates that the image is up to date. requestedTag is the tag the message
// will refer to.
func writeStatus(requestedTag string, out progress.Output, layersDownloaded bool) {
if layersDownloaded {
progress.Message(out, "", "Status: Downloaded newer image for "+requestedTag)
} else {
progress.Message(out, "", "Status: Image is up to date for "+requestedTag)
}
}
// validateRepoName validates the name of a repository.
func validateRepoName(name string) error {
if name == "" {
return fmt.Errorf("Repository name can't be empty")
}
if name == api.NoBaseImageSpecifier {
return fmt.Errorf("'%s' is a reserved name", api.NoBaseImageSpecifier)
}
return nil
}
// tmpFileClose creates a closer function for a temporary file that closes the file
// and also deletes it.
func tmpFileCloser(tmpFile *os.File) func() error {
return func() error {
tmpFile.Close()
if err := os.RemoveAll(tmpFile.Name()); err != nil {
logrus.Errorf("Failed to remove temp file: %s", tmpFile.Name())
}
return nil
}
}