docker, BlobInfoCache: try to reuse compressed blobs when pushing acr…

…oss registries

It seems we try to reuse blobs only for the specified registry, however
we can have valid known compressed digests across registry as well
following pr attempts to use that by doing following steps.

* `CandidateLocations2` now processes all known blobs and appends them
  to returned candidates at the lowest priority. As a result when
`TryReusingBlob` tries to process these candidates and if the blobs
filtered by the `Opaque` set by the `transport` fail to match then
attempt is made against all known blobs (ones which do not belong to the
current registry).

* Increase the sample set of potential blob reuse to all known
  compressed digests , also involving the one which do not belong to
current registry.

* If a blob is found match it against the registry where we are
  attempting to push. If blob is already there consider it a `CACHE
HIT!` and reply skipping blob, since its already there.

How to verify this ?

* Remove all images `buildah rmi --all` // needed so all new blobs can
  be tagged again in common bucket
* Remove any previous `blob-info-cache` by

```console
rm /home/<user>/.local/share/containers/cache/blob-info-cache-v1.boltdb
```

```console
$ skopeo copy docker://registry.fedoraproject.org/fedora-minimal docker://quay.io/fl/test:some-tag
$ buildah pull registry.fedoraproject.org/fedora-minimal
$ buildah tag registry.fedoraproject.org/fedora-minimal quay.io/fl/test
$ buildah push quay.io/fl/test
```

```console
Getting image source signatures
Copying blob a3497ca15bbf skipped: already exists
Copying config f7e02de757 done
Writing manifest to image destination
Storing signatures
```

Signed-off-by: Aditya R <arajan@redhat.com>

docker/docker_image_dest.go

@@ -345,8 +345,12 @@ func (d *dockerImageDestination) TryReusingBlobWithOptions(ctx context.Context,
 
 		// Sanity checks:
 		if reference.Domain(candidateRepo) != reference.Domain(d.ref.ref) {
-			logrus.Debugf("... Internal error: domain %s does not match destination %s", reference.Domain(candidateRepo), reference.Domain(d.ref.ref))
-			continue
+			logrus.Debugf("Found blob in a different registry: domain %s with different destination %s", reference.Domain(candidateRepo), reference.Domain(d.ref.ref))
+			// Found following blob in different registry but
+			// we need to check blob presence against the registry
+			// where we are planning to push, hence switch back the
+			// candidate repo to the one where we are planning to push.
+			candidateRepo = d.ref.ref
 		}
 		if candidateRepo.Name() == d.ref.ref.Name() && candidate.Digest == info.Digest {
 			logrus.Debug("... Already tried the primary destination")

pkg/blobinfocache/boltdb/boltdb.go

@@ -325,7 +325,67 @@ func (bdc *cache) appendReplacementCandidates(candidates []prioritize.CandidateW
 // data from previous RecordDigestUncompressedPair calls is used to also look up variants of the blob which have the same
 // uncompressed digest.
 func (bdc *cache) CandidateLocations2(transport types.ImageTransport, scope types.BICTransportScope, primaryDigest digest.Digest, canSubstitute bool) []blobinfocache.BICReplacementCandidate2 {
-	return bdc.candidateLocations(transport, scope, primaryDigest, canSubstitute, true)
+	resAllBlobs := []prioritize.CandidateWithTime{}
+	var uncompressedDigestValue digest.Digest // = ""
+	requireCompressionInfo := true
+	resultPrioritized := bdc.candidateLocations(transport, scope, primaryDigest, canSubstitute, requireCompressionInfo)
+	// Reprocess all blobs and append them to resultPrioritized in lower priority
+	if err := bdc.view(func(tx *bolt.Tx) error {
+		scopeBucket := tx.Bucket(knownLocationsBucket)
+		if scopeBucket == nil {
+			return nil
+		}
+		scopeBucket = scopeBucket.Bucket([]byte(transport.Name()))
+		if scopeBucket == nil {
+			return nil
+		}
+		if err := scopeBucket.ForEach(func(name []byte, v []byte) error {
+			bucket := scopeBucket.Bucket(name)
+			// compressionBucket won't have been created if previous writers never recorded info about compression,
+			// and we don't want to fail just because of that
+			compressionBucket := tx.Bucket(digestCompressorBucket)
+
+			resAllBlobs = append(resAllBlobs, bdc.appendReplacementCandidates(resAllBlobs, bucket, compressionBucket, primaryDigest, requireCompressionInfo)...)
+			if canSubstitute {
+				if uncompressedDigestValue = bdc.uncompressedDigest(tx, primaryDigest); uncompressedDigestValue != "" {
+					b := tx.Bucket(digestByUncompressedBucket)
+					if b != nil {
+						b = b.Bucket([]byte(uncompressedDigestValue.String()))
+						if b != nil {
+							if err := b.ForEach(func(k, _ []byte) error {
+								d, err := digest.Parse(string(k))
+								if err != nil {
+									return err
+								}
+								if d != primaryDigest && d != uncompressedDigestValue {
+									resAllBlobs = append(resAllBlobs, bdc.appendReplacementCandidates(resAllBlobs, bucket, compressionBucket, d, requireCompressionInfo)...)
+								}
+								return nil
+							}); err != nil {
+								return err
+							}
+						}
+					}
+					if uncompressedDigestValue != primaryDigest {
+						resAllBlobs = append(resAllBlobs, bdc.appendReplacementCandidates(resAllBlobs, bucket, compressionBucket, uncompressedDigestValue, requireCompressionInfo)...)
+					}
+				}
+			}
+			return nil
+		}); err != nil {
+			return err
+		}
+		return nil
+	}); err != nil {
+		return []blobinfocache.BICReplacementCandidate2{}
+	}
+
+	resultPrioritizedAllBlobs := prioritize.DestructivelyPrioritizeReplacementCandidates(resAllBlobs, primaryDigest, uncompressedDigestValue)
+	// Append `resultPrioritizedAllBlobs` after blobs
+	// which are generated from bucket with provided `scope`
+	// as a result `resultPrioritizedAllBlobs` will always
+	// get lower priority while processing candidates.
+	return append(resultPrioritized, resultPrioritizedAllBlobs...)
 }
 
 func (bdc *cache) candidateLocations(transport types.ImageTransport, scope types.BICTransportScope, primaryDigest digest.Digest, canSubstitute, requireCompressionInfo bool) []blobinfocache.BICReplacementCandidate2 {