get_size for cloud stores (#1)

cloud_blobstore/__init__.py

@@ -87,6 +87,19 @@ def get_user_metadata(
         """
         raise NotImplementedError()
 
+    def get_size(
+            self,
+            bucket: str,
+            object_name: str
+    ) -> int:
+        """
+        Retrieves the filesize
+        :param bucket: the bucket the object resides in.
+        :param object_name: the name of the object for which size is being retrieved.
+        :return: integer equal to filesize in bytes
+        """
+        raise NotImplementedError()
+
     def copy(
             self,
             src_bucket: str, src_object_name: str,

cloud_blobstore/gs.py

@@ -114,6 +114,24 @@ def get_user_metadata(
             raise BlobNotFoundError()
         return response.metadata
 
+    def get_size(
+            self,
+            bucket: str,
+            object_name: str
+    ) -> int:
+        """
+        Retrieves the filesize
+        :param bucket: the bucket the object resides in.
+        :param object_name: the name of the object for which size is being retrieved.
+        :return: integer equal to filesize in bytes
+        """
+        bucket_obj = self._ensure_bucket_loaded(bucket)
+        response = bucket_obj.get_blob(object_name)
+        if response is None:
+            raise BlobNotFoundError()
+        res = response.size
+        return res
+
     def copy(
             self,
             src_bucket: str, src_object_name: str,

cloud_blobstore/s3.py

@@ -197,6 +197,26 @@ def copy(
             ),
         )
 
+    def get_size(
+            self,
+            bucket: str,
+            object_name: str
+    ) -> int:
+        """
+        Retrieves the filesize
+        :param bucket: the bucket the object resides in.
+        :param object_name: the name of the object for which size is being retrieved.
+        :return: integer equal to filesize in bytes
+        """
+        try:
+            response = self.get_all_metadata(bucket, object_name)
+            size = response['ContentLength']
+            return size
+        except botocore.exceptions.ClientError as ex:
+            if str(ex.response['Error']['Code']) == str(requests.codes.not_found):
+                raise BlobNotFoundError(ex)
+            raise BlobStoreUnknownError(ex)
+
     def find_next_missing_parts(
             self,
             bucket: str,

tests/test_blobstore.py

@@ -104,6 +104,10 @@ def testGet(self):
                 "test_good_source_data_DOES_NOT_EXIST",
             )
 
+    def testGetSize(self):
+        sz = self.handle.get_size(self.test_fixtures_bucket, "test_good_source_data/0")
+        self.assertEqual(sz, 11358)
+
     def testCopy(self):
         dst_blob_name = infra.generate_test_key()