Fix get_blob_path to not make any database calls and add a test

This will be supported by caching, hopefully removing the need to hit the database when the blob object is cached

data/model/storage.py

@@ -248,12 +248,19 @@ def get_storage_by_uuid(storage_uuid):
 
 def get_layer_path(storage_record):
   """ Returns the path in the storage engine to the layer data referenced by the storage row. """
-  store = config.store
-  if not storage_record.cas_path:
-    logger.debug('Serving layer from legacy v1 path')
-    return store.v1_image_layer_path(storage_record.uuid)
+  return get_layer_path_for_storage(storage_record.uuid, storage_record.cas_path,
+                                    storage_record.content_checksum)
 
-  return store.blob_path(storage_record.content_checksum)
+
+def get_layer_path_for_storage(storage_uuid, cas_path, content_checksum):
+  """ Returns the path in the storage engine to the layer data referenced by the storage
+      information. """
+  store = config.store
+  if not cas_path:
+    logger.debug('Serving layer from legacy v1 path for storage %s', storage_uuid)
+    return store.v1_image_layer_path(storage_uuid)
+
+  return store.blob_path(content_checksum)
 
 
 def lookup_repo_storages_by_content_checksum(repo, checksums):

endpoints/v2/models_interface.py

@@ -41,7 +41,7 @@ class BlobUpload(
   """
 
 
-class Blob(namedtuple('Blob', ['uuid', 'digest', 'size', 'locations'])):
+class Blob(namedtuple('Blob', ['uuid', 'digest', 'size', 'locations', 'cas_path'])):
   """
   Blob represents an opaque binary blob saved to the storage system.
   """

endpoints/v2/models_pre_oci.py

@@ -211,7 +211,8 @@ class PreOCIModel(DockerRegistryV2DataInterface):
       uuid=blob_record.uuid,
       digest=blob_digest,
       size=blob_upload.byte_count,
-      locations=[blob_upload.location_name],)
+      locations=[blob_upload.location_name],
+      cas_path=blob_record.cas_path)
 
   def lookup_blobs_by_digest(self, namespace_name, repo_name, digests):
     def _blob_view(blob_record):
@@ -219,6 +220,7 @@ class PreOCIModel(DockerRegistryV2DataInterface):
         uuid=blob_record.uuid,
         digest=blob_record.content_checksum,
         size=blob_record.image_size,
+        cas_path=blob_record.cas_path,
         locations=None,  # Note: Locations is None in this case.
       )
 
@@ -235,7 +237,8 @@ class PreOCIModel(DockerRegistryV2DataInterface):
         uuid=blob_record.uuid,
         digest=digest,
         size=blob_record.image_size,
-        locations=blob_record.locations,)
+        locations=blob_record.locations,
+        cas_path=blob_record.cas_path)
     except model.BlobDoesNotExist:
       return None
 
@@ -254,8 +257,7 @@ class PreOCIModel(DockerRegistryV2DataInterface):
                                         label.media_type)
 
   def get_blob_path(self, blob):
-    blob_record = model.storage.get_storage_by_uuid(blob.uuid)
-    return model.storage.get_layer_path(blob_record)
+    return model.storage.get_layer_path_for_storage(blob.uuid, blob.cas_path, blob.digest)
 
   def set_manifest_expires_after(self, namespace_name, repo_name, digest, expires_after_sec):
     try:

endpoints/v2/test/test_models_pre_oci.py

@@ -0,0 +1,25 @@
+import hashlib
+
+from playhouse.test_utils import assert_query_count
+
+from data import model
+from data.database import ImageStorageLocation
+from endpoints.v2.models_pre_oci import data_model 
+from test.fixtures import *
+
+def test_get_blob_path(initialized_db):
+  # Add a blob.
+  digest = 'sha256:' + hashlib.sha256("a").hexdigest()
+  location = ImageStorageLocation.get(name='local_us')
+  db_blob = model.blob.store_blob_record_and_temp_link('devtable', 'simple', digest, location, 1,
+                                                       10000000)
+
+  with assert_query_count(1):
+    blob = data_model.get_blob_by_digest('devtable', 'simple', digest)
+    assert blob.uuid == db_blob.uuid
+
+  # The blob tuple should have everything get_blob_path needs, so there should be no queries.
+  with assert_query_count(0):
+    assert data_model.get_blob_path(blob)
+
+  assert data_model.get_blob_path(blob) == model.storage.get_layer_path(db_blob)