storage/remote.py: Port to new CAS downloader helper

#79

buildgrid/server/cas/storage/remote.py

@@ -23,11 +23,16 @@ Forwwards storage requests to a remote storage.
 import io
 import logging
 
+<<<<<<< HEAD
 import grpc
 
 from buildgrid.utils import gen_fetch_blob, gen_write_request_blob
+=======
+from buildgrid.client.cas import download
+>>>>>>> storage/remote.py: Port to new CAS downloader helper
 from buildgrid._protos.google.bytestream import bytestream_pb2_grpc
 from buildgrid._protos.build.bazel.remote.execution.v2 import remote_execution_pb2, remote_execution_pb2_grpc
+from buildgrid.utils import gen_write_request_blob
 
 from .storage_abc import StorageABC
 
@@ -36,7 +41,10 @@ class RemoteStorage(StorageABC):
 
     def __init__(self, channel, instance_name):
         self.logger = logging.getLogger(__name__)
-        self._instance_name = instance_name
+
+        self.instance_name = instance_name
+        self.channel = channel
+
         self._stub_bs = bytestream_pb2_grpc.ByteStreamStub(channel)
         self._stub_cas = remote_execution_pb2_grpc.ContentAddressableStorageStub(channel)
 
@@ -46,29 +54,8 @@ class RemoteStorage(StorageABC):
         return False
 
     def get_blob(self, digest):
-        try:
-            fetched_data = io.BytesIO()
-            length = 0
-
-            for data in gen_fetch_blob(self._stub_bs, digest, self._instance_name):
-                length += fetched_data.write(data)
-
-            if length:
-                assert digest.size_bytes == length
-                fetched_data.seek(0)
-                return fetched_data
-
-            else:
-                return None
-
-        except grpc.RpcError as e:
-            if e.code() == grpc.StatusCode.NOT_FOUND:
-                pass
-            else:
-                self.logger.error(e.details())
-                raise
-
-        return None
+        with download(self.channel, instance=self.instance_name) as cas:
+            return io.BytesIO(cas.get_blob(digest))
 
     def begin_write(self, digest):
         return io.BytesIO(digest.SerializeToString())