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moby--moby/graph/pull.go
Aaron Lehmann d4836cd7ec Documentation improvements and code cleanups for graph package
Expand the godoc documentation for the graph package.

Centralize DefaultTag in the graphs/tag package instead of defining it
twice.

Remove some unnecessary "config" structs that are only used to pass
a few parameters to a function.

Simplify the GetParentsSize function - there's no reason for it to take
an accumulator argument.

Unexport some functions that aren't needed outside the package.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
2015-07-30 14:27:10 -07:00

154 lines
5.3 KiB
Go

package graph
import (
"fmt"
"io"
"github.com/Sirupsen/logrus"
"github.com/docker/docker/cliconfig"
"github.com/docker/docker/pkg/streamformatter"
"github.com/docker/docker/registry"
"github.com/docker/docker/utils"
)
// 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 *cliconfig.AuthConfig
// OutStream is the output writer for showing the status of the pull
// operation.
OutStream io.Writer
}
// 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.
//
// TODO(tiborvass): have Pull() take a reference to repository + tag, so that the puller itself is repository-agnostic.
Pull(tag string) (fallback bool, err 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(s *TagStore, endpoint registry.APIEndpoint, repoInfo *registry.RepositoryInfo, imagePullConfig *ImagePullConfig, sf *streamformatter.StreamFormatter) (Puller, error) {
switch endpoint.Version {
case registry.APIVersion2:
return &v2Puller{
TagStore: s,
endpoint: endpoint,
config: imagePullConfig,
sf: sf,
repoInfo: repoInfo,
}, nil
case registry.APIVersion1:
return &v1Puller{
TagStore: s,
endpoint: endpoint,
config: imagePullConfig,
sf: sf,
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 (s *TagStore) Pull(image string, tag string, imagePullConfig *ImagePullConfig) error {
var sf = streamformatter.NewJSONStreamFormatter()
// Resolve the Repository name from fqn to RepositoryInfo
repoInfo, err := s.registryService.ResolveRepository(image)
if err != nil {
return err
}
// makes sure name is not empty or `scratch`
if err := validateRepoName(repoInfo.LocalName); err != nil {
return err
}
endpoints, err := s.registryService.LookupEndpoints(repoInfo.CanonicalName)
if err != nil {
return err
}
logName := repoInfo.LocalName
if tag != "" {
logName = utils.ImageReference(logName, tag)
}
var (
lastErr error
// 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 lastErr.
// As soon as another kind of error is encountered, discardNoSupportErrors is set to true, avoiding the saving of
// any subsequent ErrNoSupport errors in lastErr.
// 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
)
for _, endpoint := range endpoints {
logrus.Debugf("Trying to pull %s from %s %s", repoInfo.LocalName, endpoint.URL, endpoint.Version)
if !endpoint.Mirror && (endpoint.Official || endpoint.Version == registry.APIVersion2) {
if repoInfo.Official {
s.trustService.UpdateBase()
}
}
puller, err := NewPuller(s, endpoint, repoInfo, imagePullConfig, sf)
if err != nil {
lastErr = err
continue
}
if fallback, err := puller.Pull(tag); err != nil {
if fallback {
if _, ok := err.(registry.ErrNoSupport); !ok {
// Because we found an error that's not ErrNoSupport, discard all subsequent ErrNoSupport errors.
discardNoSupportErrors = true
// save the current error
lastErr = err
} else if !discardNoSupportErrors {
// Save the ErrNoSupport error, because it's either the first error or all encountered errors
// were also ErrNoSupport errors.
lastErr = err
}
continue
}
logrus.Debugf("Not continuing with error: %v", err)
return err
}
s.eventsService.Log("pull", logName, "")
return nil
}
if lastErr == nil {
lastErr = fmt.Errorf("no endpoints found for %s", image)
}
return lastErr
}
// 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 io.Writer, sf *streamformatter.StreamFormatter, layersDownloaded bool) {
if layersDownloaded {
out.Write(sf.FormatStatus("", "Status: Downloaded newer image for %s", requestedTag))
} else {
out.Write(sf.FormatStatus("", "Status: Image is up to date for %s", requestedTag))
}
}