Add a container_infor_cache param to upload_object

Each upload involves a request that retrieves block size and hash information.
In higher level applications, this request is redudant after the first upload.
This feature allows higher level operations to cache retrieved container info
in a session.

Refs: #3707

kamaki/clients/pithos/__init__.py

@@ -196,8 +196,23 @@ class PithosClient(PithosRestClient):
             format='json')
         assert r.json[0] == hash, 'Local hash does not match server'
 
-    def _get_file_block_info(self, fileobj, size=None):
-        meta = self.get_container_info()
+    def _get_file_block_info(self, fileobj, size=None, cache=None):
+        """
+        :param fileobj: (file descriptor) source
+
+        :param size: (int) size of data to upload from source
+
+        :param cache: (dict) if provided, cache container info response to
+        avoid redundant calls
+        """
+        if isinstance(cache, dict):
+            try:
+                meta = cache[self.container]
+            except KeyError:
+                meta = self.get_container_info()
+                cache[self.container] = meta
+        else:
+            meta = self.get_container_info()
         blocksize = int(meta['x-container-block-size'])
         blockhash = meta['x-container-block-hash']
         size = size if size is not None else fstat(fileobj.fileno()).st_size
@@ -307,7 +322,8 @@ class PithosClient(PithosRestClient):
             content_disposition=None,
             content_type=None,
             sharing=None,
-            public=None):
+            public=None,
+            container_info_cache=None):
         """Upload an object using multiple connections (threads)
 
         :param obj: (str) remote object path
@@ -338,12 +354,15 @@ class PithosClient(PithosRestClient):
             'write':[usr and/or grp names]}
 
         :param public: (bool)
+
+        :param container_info_cache: (dict) if given, avoid redundant calls to
+        server for container info (block size and hash information)
         """
         self._assert_container()
 
         #init
         block_info = (blocksize, blockhash, size, nblocks) =\
-            self._get_file_block_info(f, size)
+            self._get_file_block_info(f, size, container_info_cache)
         (hashes, hmap, offset) = ([], {}, 0)
         if not content_type:
             content_type = 'application/octet-stream'