distribution/docs/storage/layerreader.go
Stephen J Day 6ab228f798 Integrate layer info cache with registry and storage
This changeset integrates the layer info cache with the registry webapp and
storage backend. The main benefit is to cache immutable layer meta data,
reducing backend roundtrips. The cache can be configured to use either redis or
an inmemory cache.

This provides massive performance benefits for HEAD http checks on layer blobs
and manifest verification.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
2015-04-02 20:15:16 -07:00

80 lines
1.9 KiB
Go

package storage
import (
"net/http"
"time"
"github.com/docker/distribution"
"github.com/docker/distribution/digest"
"github.com/docker/distribution/registry/storage/driver"
)
// layerReader implements Layer and provides facilities for reading and
// seeking.
type layerReader struct {
fileReader
digest digest.Digest
}
// newLayerReader returns a new layerReader with the digest, path and length,
// eliding round trips to the storage backend.
func newLayerReader(driver driver.StorageDriver, dgst digest.Digest, path string, length int64) (*layerReader, error) {
fr := &fileReader{
driver: driver,
path: path,
size: length,
}
return &layerReader{
fileReader: *fr,
digest: dgst,
}, nil
}
var _ distribution.Layer = &layerReader{}
func (lr *layerReader) Digest() digest.Digest {
return lr.digest
}
func (lr *layerReader) Length() int64 {
return lr.size
}
func (lr *layerReader) CreatedAt() time.Time {
return lr.modtime
}
// Close the layer. Should be called when the resource is no longer needed.
func (lr *layerReader) Close() error {
return lr.closeWithErr(distribution.ErrLayerClosed)
}
func (lr *layerReader) Handler(r *http.Request) (h http.Handler, err error) {
var handlerFunc http.HandlerFunc
redirectURL, err := lr.fileReader.driver.URLFor(lr.path, map[string]interface{}{"method": r.Method})
switch err {
case nil:
handlerFunc = func(w http.ResponseWriter, r *http.Request) {
// Redirect to storage URL.
http.Redirect(w, r, redirectURL, http.StatusTemporaryRedirect)
}
case driver.ErrUnsupportedMethod:
handlerFunc = func(w http.ResponseWriter, r *http.Request) {
// Fallback to serving the content directly.
http.ServeContent(w, r, lr.digest.String(), lr.CreatedAt(), lr)
}
default:
// Some unexpected error.
return nil, err
}
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Docker-Content-Digest", lr.digest.String())
handlerFunc.ServeHTTP(w, r)
}), nil
}