add support for empty start time in database service connections (aggregator)...

add support for empty start time in database service connections (aggregator) and core schedule representation (third patch)

datafiles/schema.sql

@@ -39,7 +39,7 @@ CREATE TABLE service_connections (
     dest_network            text                        NOT NULL,
     dest_port               text                        NOT NULL,
     dest_label              label,
-    start_time              timestamp                   NOT NULL,
+    start_time              timestamp,                            -- null = now
     end_time                timestamp                   NOT NULL,
     symmetrical             boolean                     NOT NULL,
     directionality          directionality              NOT NULL,

opennsa/nsa.py

@@ -375,7 +375,8 @@ class Schedule(object):
 
     def __init__(self, start_time, end_time):
         # Must be datetime instances without tzinfo
-        assert start_time.tzinfo is None, 'Start time must NOT have time zone'
+        if start_time is not None:
+            assert start_time.tzinfo is None, 'Start time must NOT have time zone'
         assert end_time.tzinfo   is None, 'End time must NOT have time zone'
 
         self.start_time = start_time