Merge pull request #130 from minrk/reflector-init-wait

Allow waiting for reflectors to get initial data

kubespawner/reflector.py

@@ -1,3 +1,7 @@
+# specifically use concurrent.futures for threadsafety
+# asyncio Futures cannot be used across threads
+from concurrent.futures import Future
+
 import time
 import threading
 
@@ -6,6 +10,7 @@
 from kubernetes import client, config, watch
 from tornado.ioloop import IOLoop
 
+
 class NamespacedResourceReflector(LoggingConfigurable):
     """
     Base class for keeping a local up-to-date copy of a set of kubernetes resources.
@@ -84,6 +89,8 @@ def __init__(self, *args, **kwargs):
         # FIXME: Protect against malicious labels?
         self.label_selector = ','.join(['{}={}'.format(k, v) for k, v in self.labels.items()])
 
+        self.first_load_future = Future()
+
         self.start()
 
     def _list_and_update(self):
@@ -130,6 +137,9 @@ def _watch_and_update(self):
             w = watch.Watch()
             try:
                 resource_version = self._list_and_update()
+                if not self.first_load_future.done():
+                    # signal that we've loaded our initial data
+                    self.first_load_future.set_result(None)
                 for ev in w.stream(
                         getattr(self.api, self.list_method_name),
                         self.namespace,

kubespawner/spawner.py

@@ -970,6 +970,9 @@ def poll(self):
         Returns None if it is, and 1 if it isn't. These are the return values
         JupyterHub expects.
         """
+        # have to wait for first load of data before we have a valid answer
+        if not self.pod_reflector.first_load_future.done():
+            yield self.pod_reflector.first_load_future
         data = self.pod_reflector.pods.get(self.pod_name, None)
         if data is not None:
             return None