[feature] consume received stream in a thread

As it's blocking and Twisted already stored everything on a file.

-- Related: #8809

src/leap/soledad/server/_streaming_resource.py

@@ -25,7 +25,7 @@ import base64
 
 from zope.interface import implementer
 from twisted.internet.interfaces import IPushProducer
-from twisted.internet import task, defer
+from twisted.internet import task, defer, threads
 from twisted.web.server import NOT_DONE_YET
 from twisted.web.resource import Resource
 
@@ -75,11 +75,19 @@ class StreamingResource(Resource):
         # TODO: at this point, Twisted wrote the request to a temporary file,
         # so it's a disk->disk operation. This has to be improved if benchmark
         # shows its worth.
+        args = (user, namespace, request)
+        d = threads.deferToThread(self._consume_stream, *args)
+        d.addCallback(lambda _: request.finish())
+
+        return NOT_DONE_YET
+
+    def _consume_stream(self, user, namespace, request):
+        chunk_size = 2**14
         content = request.content
         incoming_list = json.loads(content.readline())
-        # TODO: NEEDS SANITIZING
         for (blob_id, size) in incoming_list:
             db = self._handler
+            # TODO: NEEDS SANITIZING
             path = db._get_path(user, blob_id, namespace)
             try:
                 mkdir_p(os.path.split(path)[0])
@@ -88,11 +96,10 @@ class StreamingResource(Resource):
             with open(path, 'wb') as blob_fd:
                 consumed = 0
                 while consumed < size:
-                    read_size = min(size - consumed, 2**16)
+                    read_size = min(size - consumed, chunk_size)
                     data = content.read(read_size)
                     consumed += read_size
                     blob_fd.write(data)
-        return ''
 
     def _startDownstream(self, user, namespace, request):
         raw_content = request.content.read()