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// Package memory implements an in-memory BlobInfoCache.
package memory
import (
"sync"
"time"
"github.com/containers/image/v5/internal/blobinfocache"
"github.com/containers/image/v5/internal/set"
"github.com/containers/image/v5/pkg/blobinfocache/internal/prioritize"
"github.com/containers/image/v5/types"
digest "github.com/opencontainers/go-digest"
"github.com/sirupsen/logrus"
)
// locationKey only exists to make lookup in knownLocations easier.
type locationKey struct {
transport string
scope types.BICTransportScope
blobDigest digest.Digest
}
// cache implements an in-memory-only BlobInfoCache.
type cache struct {
mutex sync.Mutex
// The following fields can only be accessed with mutex held.
uncompressedDigests map[digest.Digest]digest.Digest
digestsByUncompressed map[digest.Digest]*set.Set[digest.Digest] // stores a set of digests for each uncompressed digest
knownLocations map[locationKey]map[types.BICLocationReference]time.Time // stores last known existence time for each location reference
compressors map[digest.Digest]string // stores a compressor name, or blobinfocache.Unknown, for each digest
}
// New returns a BlobInfoCache implementation which is in-memory only.
//
// This is primarily intended for tests, but also used as a fallback
// if blobinfocache.DefaultCache can’t determine, or set up, the
// location for a persistent cache. Most users should use
// blobinfocache.DefaultCache. instead of calling this directly.
// Manual users of types.{ImageSource,ImageDestination} might also use
// this instead of a persistent cache.
func New() types.BlobInfoCache {
return new2()
}
func new2() *cache {
return &cache{
uncompressedDigests: map[digest.Digest]digest.Digest{},
digestsByUncompressed: map[digest.Digest]*set.Set[digest.Digest]{},
knownLocations: map[locationKey]map[types.BICLocationReference]time.Time{},
compressors: map[digest.Digest]string{},
}
}
// UncompressedDigest returns an uncompressed digest corresponding to anyDigest.
// May return anyDigest if it is known to be uncompressed.
// Returns "" if nothing is known about the digest (it may be compressed or uncompressed).
func (mem *cache) UncompressedDigest(anyDigest digest.Digest) digest.Digest {
mem.mutex.Lock()
defer mem.mutex.Unlock()
return mem.uncompressedDigestLocked(anyDigest)
}
// uncompressedDigestLocked implements types.BlobInfoCache.UncompressedDigest, but must be called only with mem.mutex held.
func (mem *cache) uncompressedDigestLocked(anyDigest digest.Digest) digest.Digest {
if d, ok := mem.uncompressedDigests[anyDigest]; ok {
return d
}
// Presence in digestsByUncompressed implies that anyDigest must already refer to an uncompressed digest.
// This way we don't have to waste storage space with trivial (uncompressed, uncompressed) mappings
// when we already record a (compressed, uncompressed) pair.
if s, ok := mem.digestsByUncompressed[anyDigest]; ok && !s.Empty() {
return anyDigest
}
return ""
}
// RecordDigestUncompressedPair records that the uncompressed version of anyDigest is uncompressed.
// It’s allowed for anyDigest == uncompressed.
// WARNING: Only call this for LOCALLY VERIFIED data; don’t record a digest pair just because some remote author claims so (e.g.
// because a manifest/config pair exists); otherwise the cache could be poisoned and allow substituting unexpected blobs.
// (Eventually, the DiffIDs in image config could detect the substitution, but that may be too late, and not all image formats contain that data.)
func (mem *cache) RecordDigestUncompressedPair(anyDigest digest.Digest, uncompressed digest.Digest) {
mem.mutex.Lock()
defer mem.mutex.Unlock()
if previous, ok := mem.uncompressedDigests[anyDigest]; ok && previous != uncompressed {
logrus.Warnf("Uncompressed digest for blob %s previously recorded as %s, now %s", anyDigest, previous, uncompressed)
}
mem.uncompressedDigests[anyDigest] = uncompressed
anyDigestSet, ok := mem.digestsByUncompressed[uncompressed]
if !ok {
anyDigestSet = set.New[digest.Digest]()
mem.digestsByUncompressed[uncompressed] = anyDigestSet
}
anyDigestSet.Add(anyDigest)
}
// RecordKnownLocation records that a blob with the specified digest exists within the specified (transport, scope) scope,
// and can be reused given the opaque location data.
func (mem *cache) RecordKnownLocation(transport types.ImageTransport, scope types.BICTransportScope, blobDigest digest.Digest, location types.BICLocationReference) {
mem.mutex.Lock()
defer mem.mutex.Unlock()
key := locationKey{transport: transport.Name(), scope: scope, blobDigest: blobDigest}
locationScope, ok := mem.knownLocations[key]
if !ok {
locationScope = map[types.BICLocationReference]time.Time{}
mem.knownLocations[key] = locationScope
}
locationScope[location] = time.Now() // Possibly overwriting an older entry.
}
// RecordDigestCompressorName records that the blob with the specified digest is either compressed with the specified
// algorithm, or uncompressed, or that we no longer know.
func (mem *cache) RecordDigestCompressorName(blobDigest digest.Digest, compressorName string) {
mem.mutex.Lock()
defer mem.mutex.Unlock()
if compressorName == blobinfocache.UnknownCompression {
delete(mem.compressors, blobDigest)
return
}
mem.compressors[blobDigest] = compressorName
}
// appendReplacementCandidates creates prioritize.CandidateWithTime values for (transport, scope, digest), and returns the result of appending them to candidates.
func (mem *cache) appendReplacementCandidates(candidates []prioritize.CandidateWithTime, transport types.ImageTransport, scope types.BICTransportScope, digest digest.Digest, requireCompressionInfo bool) []prioritize.CandidateWithTime {
locations := mem.knownLocations[locationKey{transport: transport.Name(), scope: scope, blobDigest: digest}] // nil if not present
for l, t := range locations {
compressorName, compressorKnown := mem.compressors[digest]
if !compressorKnown {
if requireCompressionInfo {
continue
}
compressorName = blobinfocache.UnknownCompression
}
candidates = append(candidates, prioritize.CandidateWithTime{
Candidate: blobinfocache.BICReplacementCandidate2{
Digest: digest,
CompressorName: compressorName,
Location: l,
},
LastSeen: t,
})
}
return candidates
}
// CandidateLocations returns a prioritized, limited, number of blobs and their locations that could possibly be reused
// within the specified (transport scope) (if they still exist, which is not guaranteed).
//
// If !canSubstitute, the returned candidates will match the submitted digest exactly; if canSubstitute,
// data from previous RecordDigestUncompressedPair calls is used to also look up variants of the blob which have the same
// uncompressed digest.
func (mem *cache) CandidateLocations(transport types.ImageTransport, scope types.BICTransportScope, primaryDigest digest.Digest, canSubstitute bool) []types.BICReplacementCandidate {
return blobinfocache.CandidateLocationsFromV2(mem.candidateLocations(transport, scope, primaryDigest, canSubstitute, false))
}
// CandidateLocations2 returns a prioritized, limited, number of blobs and their locations that could possibly be reused
// within the specified (transport scope) (if they still exist, which is not guaranteed).
//
// If !canSubstitute, the returned cadidates will match the submitted digest exactly; if canSubstitute,
// data from previous RecordDigestUncompressedPair calls is used to also look up variants of the blob which have the same
// uncompressed digest.
func (mem *cache) CandidateLocations2(transport types.ImageTransport, scope types.BICTransportScope, primaryDigest digest.Digest, canSubstitute bool) []blobinfocache.BICReplacementCandidate2 {
return mem.candidateLocations(transport, scope, primaryDigest, canSubstitute, true)
}
func (mem *cache) candidateLocations(transport types.ImageTransport, scope types.BICTransportScope, primaryDigest digest.Digest, canSubstitute, requireCompressionInfo bool) []blobinfocache.BICReplacementCandidate2 {
mem.mutex.Lock()
defer mem.mutex.Unlock()
res := []prioritize.CandidateWithTime{}
res = mem.appendReplacementCandidates(res, transport, scope, primaryDigest, requireCompressionInfo)
var uncompressedDigest digest.Digest // = ""
if canSubstitute {
if uncompressedDigest = mem.uncompressedDigestLocked(primaryDigest); uncompressedDigest != "" {
if otherDigests, ok := mem.digestsByUncompressed[uncompressedDigest]; ok {
for _, d := range otherDigests.Values() {
if d != primaryDigest && d != uncompressedDigest {
res = mem.appendReplacementCandidates(res, transport, scope, d, requireCompressionInfo)
}
}
}
if uncompressedDigest != primaryDigest {
res = mem.appendReplacementCandidates(res, transport, scope, uncompressedDigest, requireCompressionInfo)
}
}
}
return prioritize.DestructivelyPrioritizeReplacementCandidates(res, primaryDigest, uncompressedDigest)
}
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