Fix serialization of blobs to/from the cache

Also makes sure the test checks that serialization

data/cache/impl.py

@@ -48,7 +48,7 @@ class InMemoryDataModelCache(DataModelCache):
     result = self.cache.get(cache_key.key, default_value=not_found)
     if result != not_found:
       logger.debug('Found result in cache for key %s: %s', cache_key.key, result)
-      return result
+      return json.loads(result)
 
     logger.debug('Found no result in cache for key %s; calling loader', cache_key.key)
     result = loader()
@@ -57,7 +57,7 @@ class InMemoryDataModelCache(DataModelCache):
       logger.debug('Caching loaded result for key %s with expiration %s: %s', cache_key.key,
                    result, cache_key.expiration)
       expires = convert_to_timedelta(cache_key.expiration) + datetime.now()
-      self.cache.set(cache_key.key, result, expires=expires)
+      self.cache.set(cache_key.key, json.dumps(result), expires=expires)
       logger.debug('Cached loaded result for key %s with expiration %s: %s', cache_key.key,
                    result, cache_key.expiration)
     else:

endpoints/v2/blob.py

@@ -16,6 +16,7 @@ from endpoints.decorators import anon_protect, parse_repository_name
 from endpoints.v2 import v2_bp, require_repo_read, require_repo_write, get_input_stream
 from endpoints.v2.errors import (
   BlobUnknown, BlobUploadInvalid, BlobUploadUnknown, Unsupported, NameUnknown, LayerTooLarge)
+from endpoints.v2.models_interface import Blob
 from endpoints.v2.models_pre_oci import data_model as model
 from util.cache import cache_control
 from util.registry.filelike import wrap_with_handler, StreamSlice
@@ -40,11 +41,16 @@ def _get_repository_blob(namespace_name, repo_name, digest):
       Automatically handles caching.
   """
   def load_blob():
-    return model.get_blob_by_digest(namespace_name, repo_name, digest)
+    blob = model.get_blob_by_digest(namespace_name, repo_name, digest)
+    if blob is None:
+      return None
+    
+    return blob._asdict()
 
   blob_cache_key = cache_key.for_repository_blob(namespace_name, repo_name, digest)
-  return model_cache.retrieve(blob_cache_key, load_blob)
-
+  blob_dict = model_cache.retrieve(blob_cache_key, load_blob)
+  return Blob(**blob_dict) if blob_dict is not None else None
+  
 
 @v2_bp.route(BLOB_DIGEST_ROUTE, methods=['HEAD'])
 @parse_repository_name()

endpoints/v2/models_pre_oci.py

@@ -227,7 +227,7 @@ class PreOCIModel(DockerRegistryV2DataInterface):
         uuid=blob_record.uuid,
         digest=digest,
         size=blob_record.image_size,
-        locations=blob_record.locations,
+        locations=list(blob_record.locations),
         cas_path=blob_record.cas_path
       )
     except model.BlobDoesNotExist: