relay: hack in utils.schedulers so that exportDB only gets queued once globally

Previously, exportDB would be queued once by every IRC object, which was the wrong behavior!

plugins/relay.py

@@ -22,9 +22,9 @@ def loadDB():
             ", creating a new one in memory...", dbname)
         db = {}
 
-def exportDB():
-    scheduler.enter(10, 1, exportDB)
-    log.debug("Relay: exporting links database to "+dbname)
+def exportDB(scheduler):
+    scheduler.enter(60, 1, exportDB, argument=(scheduler,))
+    log.debug("Relay: exporting links database to %s", dbname)
     with open(dbname, 'wb') as f:
         pickle.dump(db, f, protocol=4)
 
@@ -77,10 +77,16 @@ def destroy(irc, source, args):
         utils.msg(irc, source, 'Error: no such relay %r exists.' % channel)
 
 def main(irc):
-    global scheduler
-    scheduler = sched.scheduler()
+
     loadDB()
-    scheduler.enter(60, 1, exportDB)
+    # HACK: we only want to schedule this once globally, because
+    # exportDB will otherwise be called by every network that loads this
+    # plugin.
+    if 'relaydb' not in utils.schedulers:
+        utils.schedulers['relaydb'] = scheduler = sched.scheduler()
+        scheduler.enter(30, 1, exportDB, argument=(scheduler,))
+        # Thread this because exportDB() queues itself as part of its
+        # execution, in order to get a repeating loop.
         thread = threading.Thread(target=scheduler.run)
         thread.start()
     for chanpair in db:

utils.py

@@ -9,6 +9,7 @@ global bot_commands, command_hooks
 bot_commands = {}
 command_hooks = defaultdict(list)
 networkobjects = {}
+schedulers = {}
 
 class TS6UIDGenerator():
     """TS6 UID Generator module, adapted from InspIRCd source