remote/coordinator: move yaml generation off the main loop

With many resources, yaml.dump(resources) takes a few seconds. To avoid
blocking the main loop for this long, make a copy and serialize via a
threaded executor.

Signed-off-by: Jan Luebbe <jlu@pengutronix.de>

Author: jluebbe

labgrid/remote/coordinator.py

@@ -7,6 +7,7 @@
 from functools import wraps
 import time
 from contextlib import contextmanager
+import copy
 
 import attr
 import grpc
@@ -267,19 +268,24 @@ async def save(self):
         logging.debug("Running Save")
         self.save_scheduled = False
 
-        with warn_if_slow("dump resources"):
-            resources = self._get_resources()
-            resources = yaml.dump(resources)
-            resources = resources.encode()
-        with warn_if_slow("dump places"):
-            places = self._get_places()
-            places = yaml.dump(places)
-            places = places.encode()
-
-        logging.debug("Awaiting resources")
-        await self.loop.run_in_executor(None, atomic_replace, "resources.yaml", resources)
-        logging.debug("Awaiting places")
-        await self.loop.run_in_executor(None, atomic_replace, "places.yaml", places)
+        with warn_if_slow("create resources snapshot"):
+            resources = copy.deepcopy(self._get_resources())
+        with warn_if_slow("create places snapshot"):
+            places = copy.deepcopy(self._get_places())
+
+        def save_sync(resources, places):
+            with warn_if_slow("dump resources"):
+                resources = yaml.dump(resources)
+                resources = resources.encode()
+            with warn_if_slow("dump places"):
+                places = yaml.dump(places)
+                places = places.encode()
+            with warn_if_slow("write resources"):
+                atomic_replace("resources.yaml", resources)
+            with warn_if_slow("write places"):
+                atomic_replace("places.yaml", places)
+
+        await self.loop.run_in_executor(None, save_sync, resources, places)
 
     def load(self):
         try: