Resurrecting poll_until

reddwarf/common/exception.py

@@ -130,3 +130,6 @@ class BadValue(ReddwarfError):
 
     message = _("Value could not be converted: %(msg)s")
 
+
+class PollTimeOut(ReddwarfError):
+    message = _("Polling request timed out.")

reddwarf/common/utils.py

@@ -22,6 +22,7 @@ import logging
 import re
 import signal
 import sys
+import time
 import urlparse
 import uuid
 
@@ -207,6 +208,26 @@ class LoopingCall(object):
         return self.done.wait()
 
 
+def poll_until(retriever, condition=lambda value: value,
+               sleep_time=1, time_out=None):
+    """Retrieves object until it passes condition, then returns it.
+
+    If time_out_limit is passed in, PollTimeOut will be raised once that
+    amount of time is eclipsed.
+
+    """
+    start_time = time.time()
+
+    def poll_and_check():
+        obj = retriever()
+        if condition(obj):
+            raise LoopingCallDone(retvalue=obj)
+        if time_out is not None and time.time() > start_time + time_out:
+            raise exception.PollTimeOut
+    lc = LoopingCall(f=poll_and_check).start(sleep_time, True)
+    return lc.wait()
+
+
 # Copied from nova.api.openstack.common in the old code.
 def get_id_from_href(href):
     """Return the id or uuid portion of a url.