distribution/docs/storage/cache/memory.go
Stephen J Day a7c2dceea5 Define and implement layer info cache
This changeset defines the interface for layer info caches. Layer info caches
speed up access to layer meta data accessed in storage driver backends. The
two main operations are tests for repository membership and resolving path and
size information for backend blobs.

Two implementations are available. The main implementation leverages redis to
store layer info. An alternative implementation simply caches layer info in
maps, which should speed up resolution for less sophisticated implementations.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
2015-04-02 20:15:09 -07:00

63 lines
1.7 KiB
Go

package cache
import (
"github.com/docker/distribution/digest"
"golang.org/x/net/context"
)
// inmemoryLayerInfoCache is a map-based implementation of LayerInfoCache.
type inmemoryLayerInfoCache struct {
membership map[string]map[digest.Digest]struct{}
meta map[digest.Digest]LayerMeta
}
// NewInMemoryLayerInfoCache provides an implementation of LayerInfoCache that
// stores results in memory.
func NewInMemoryLayerInfoCache() LayerInfoCache {
return &base{&inmemoryLayerInfoCache{
membership: make(map[string]map[digest.Digest]struct{}),
meta: make(map[digest.Digest]LayerMeta),
}}
}
func (ilic *inmemoryLayerInfoCache) Contains(ctx context.Context, repo string, dgst digest.Digest) (bool, error) {
members, ok := ilic.membership[repo]
if !ok {
return false, nil
}
_, ok = members[dgst]
return ok, nil
}
// Add adds the layer to the redis repository blob set.
func (ilic *inmemoryLayerInfoCache) Add(ctx context.Context, repo string, dgst digest.Digest) error {
members, ok := ilic.membership[repo]
if !ok {
members = make(map[digest.Digest]struct{})
ilic.membership[repo] = members
}
members[dgst] = struct{}{}
return nil
}
// Meta retrieves the layer meta data from the redis hash, returning
// ErrUnknownLayer if not found.
func (ilic *inmemoryLayerInfoCache) Meta(ctx context.Context, dgst digest.Digest) (LayerMeta, error) {
meta, ok := ilic.meta[dgst]
if !ok {
return LayerMeta{}, ErrNotFound
}
return meta, nil
}
// SetMeta sets the meta data for the given digest using a redis hash. A hash
// is used here since we may store unrelated fields about a layer in the
// future.
func (ilic *inmemoryLayerInfoCache) SetMeta(ctx context.Context, dgst digest.Digest, meta LayerMeta) error {
ilic.meta[dgst] = meta
return nil
}