Make starting pushers faster during start up

We start all pushers on start up and immediately start a background
process to fetch push to send. This makes start up incredibly painful
when dealing with many pushers.

Instead, let's do a quick fast DB check to see if there *may* be push to
send and only start the background processes for those pushers. We also
stagger starting up and doing those checks so that we don't try and
handle all pushers at once.

1 files changed, 10 insertions, 2 deletions

diff --git a/synapse/push/httppusher.py b/synapse/push/httppusher.py
index e65f8c63d3..fac05aa44c 100644
--- a/synapse/push/httppusher.py
+++ b/synapse/push/httppusher.py
@@ -112,8 +112,16 @@ class HttpPusher(object):
         self.data_minus_url.update(self.data)
         del self.data_minus_url['url']
 
-    def on_started(self):
-        self._start_processing()
+    def on_started(self, should_check_for_notifs):
+        """Called when this pusher has been started.
+
+        Args:
+            should_check_for_notifs (bool): Whether we should immediately
+                check for push to send. Set to False only if it's known there
+                is nothing to send
+        """
+        if should_check_for_notifs:
+            self._start_processing()
 
     def on_new_notifications(self, min_stream_ordering, max_stream_ordering):
         self.max_stream_ordering = max(max_stream_ordering, self.max_stream_ordering or 0)