324 lines
		
	
	
		
			12 KiB
		
	
	
	
		
			Python
		
	
	
			
		
		
	
	
			324 lines
		
	
	
		
			12 KiB
		
	
	
	
		
			Python
		
	
	
# -*- coding: utf-8 -*-
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# Copyright 2016 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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#     http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import logging
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from twisted.internet.error import AlreadyCalled, AlreadyCancelled
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from synapse.metrics.background_process_metrics import run_as_background_process
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from synapse.types import RoomStreamToken
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logger = logging.getLogger(__name__)
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# The amount of time we always wait before ever emailing about a notification
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# (to give the user a chance to respond to other push or notice the window)
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DELAY_BEFORE_MAIL_MS = 10 * 60 * 1000
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# THROTTLE is the minimum time between mail notifications sent for a given room.
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# Each room maintains its own throttle counter, but each new mail notification
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# sends the pending notifications for all rooms.
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THROTTLE_START_MS = 10 * 60 * 1000
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THROTTLE_MAX_MS = 24 * 60 * 60 * 1000  # 24h
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# THROTTLE_MULTIPLIER = 6              # 10 mins, 1 hour, 6 hours, 24 hours
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THROTTLE_MULTIPLIER = 144  # 10 mins, 24 hours - i.e. jump straight to 1 day
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# If no event triggers a notification for this long after the previous,
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# the throttle is released.
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# 12 hours - a gap of 12 hours in conversation is surely enough to merit a new
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# notification when things get going again...
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THROTTLE_RESET_AFTER_MS = 12 * 60 * 60 * 1000
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# does each email include all unread notifs, or just the ones which have happened
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# since the last mail?
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# XXX: this is currently broken as it includes ones from parted rooms(!)
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INCLUDE_ALL_UNREAD_NOTIFS = False
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class EmailPusher:
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    """
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    A pusher that sends email notifications about events (approximately)
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    when they happen.
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    This shares quite a bit of code with httpusher: it would be good to
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    factor out the common parts
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    """
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    def __init__(self, hs, pusherdict, mailer):
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        self.hs = hs
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        self.mailer = mailer
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        self.store = self.hs.get_datastore()
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        self.clock = self.hs.get_clock()
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        self.pusher_id = pusherdict["id"]
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        self.user_id = pusherdict["user_name"]
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        self.app_id = pusherdict["app_id"]
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        self.email = pusherdict["pushkey"]
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        self.last_stream_ordering = pusherdict["last_stream_ordering"]
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        self.timed_call = None
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        self.throttle_params = None
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        # See httppusher
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        self.max_stream_ordering = None
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        self._is_processing = False
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    def on_started(self, should_check_for_notifs):
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        """Called when this pusher has been started.
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        Args:
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            should_check_for_notifs (bool): Whether we should immediately
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                check for push to send. Set to False only if it's known there
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                is nothing to send
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        """
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        if should_check_for_notifs and self.mailer is not None:
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            self._start_processing()
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    def on_stop(self):
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        if self.timed_call:
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            try:
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                self.timed_call.cancel()
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            except (AlreadyCalled, AlreadyCancelled):
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                pass
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            self.timed_call = None
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    def on_new_notifications(self, max_token: RoomStreamToken):
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        # We just use the minimum stream ordering and ignore the vector clock
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        # component. This is safe to do as long as we *always* ignore the vector
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        # clock components.
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        max_stream_ordering = max_token.stream
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        if self.max_stream_ordering:
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            self.max_stream_ordering = max(
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                max_stream_ordering, self.max_stream_ordering
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            )
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        else:
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            self.max_stream_ordering = max_stream_ordering
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        self._start_processing()
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    def on_new_receipts(self, min_stream_id, max_stream_id):
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        # We could wake up and cancel the timer but there tend to be quite a
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        # lot of read receipts so it's probably less work to just let the
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        # timer fire
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        pass
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    def on_timer(self):
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        self.timed_call = None
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        self._start_processing()
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    def _start_processing(self):
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        if self._is_processing:
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            return
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        run_as_background_process("emailpush.process", self._process)
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    def _pause_processing(self):
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        """Used by tests to temporarily pause processing of events.
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        Asserts that its not currently processing.
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        """
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        assert not self._is_processing
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        self._is_processing = True
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    def _resume_processing(self):
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        """Used by tests to resume processing of events after pausing.
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        """
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        assert self._is_processing
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        self._is_processing = False
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        self._start_processing()
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    async def _process(self):
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        # we should never get here if we are already processing
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        assert not self._is_processing
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        try:
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            self._is_processing = True
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            if self.throttle_params is None:
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                # this is our first loop: load up the throttle params
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                self.throttle_params = await self.store.get_throttle_params_by_room(
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                    self.pusher_id
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                )
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            # if the max ordering changes while we're running _unsafe_process,
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            # call it again, and so on until we've caught up.
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            while True:
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                starting_max_ordering = self.max_stream_ordering
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                try:
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                    await self._unsafe_process()
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                except Exception:
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                    logger.exception("Exception processing notifs")
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                if self.max_stream_ordering == starting_max_ordering:
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                    break
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        finally:
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            self._is_processing = False
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    async def _unsafe_process(self):
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        """
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        Main logic of the push loop without the wrapper function that sets
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        up logging, measures and guards against multiple instances of it
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        being run.
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        """
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        start = 0 if INCLUDE_ALL_UNREAD_NOTIFS else self.last_stream_ordering
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        fn = self.store.get_unread_push_actions_for_user_in_range_for_email
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        unprocessed = await fn(self.user_id, start, self.max_stream_ordering)
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        soonest_due_at = None
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        if not unprocessed:
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            await self.save_last_stream_ordering_and_success(self.max_stream_ordering)
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            return
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        for push_action in unprocessed:
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            received_at = push_action["received_ts"]
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            if received_at is None:
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                received_at = 0
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            notif_ready_at = received_at + DELAY_BEFORE_MAIL_MS
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            room_ready_at = self.room_ready_to_notify_at(push_action["room_id"])
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            should_notify_at = max(notif_ready_at, room_ready_at)
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            if should_notify_at < self.clock.time_msec():
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                # one of our notifications is ready for sending, so we send
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                # *one* email updating the user on their notifications,
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                # we then consider all previously outstanding notifications
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                # to be delivered.
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                reason = {
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                    "room_id": push_action["room_id"],
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                    "now": self.clock.time_msec(),
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                    "received_at": received_at,
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                    "delay_before_mail_ms": DELAY_BEFORE_MAIL_MS,
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                    "last_sent_ts": self.get_room_last_sent_ts(push_action["room_id"]),
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                    "throttle_ms": self.get_room_throttle_ms(push_action["room_id"]),
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                }
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                await self.send_notification(unprocessed, reason)
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                await self.save_last_stream_ordering_and_success(
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                    max(ea["stream_ordering"] for ea in unprocessed)
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                )
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                # we update the throttle on all the possible unprocessed push actions
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                for ea in unprocessed:
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                    await self.sent_notif_update_throttle(ea["room_id"], ea)
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                break
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            else:
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                if soonest_due_at is None or should_notify_at < soonest_due_at:
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                    soonest_due_at = should_notify_at
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                if self.timed_call is not None:
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                    try:
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                        self.timed_call.cancel()
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                    except (AlreadyCalled, AlreadyCancelled):
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                        pass
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                    self.timed_call = None
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        if soonest_due_at is not None:
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            self.timed_call = self.hs.get_reactor().callLater(
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                self.seconds_until(soonest_due_at), self.on_timer
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            )
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    async def save_last_stream_ordering_and_success(self, last_stream_ordering):
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        if last_stream_ordering is None:
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            # This happens if we haven't yet processed anything
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            return
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        self.last_stream_ordering = last_stream_ordering
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        pusher_still_exists = await self.store.update_pusher_last_stream_ordering_and_success(
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            self.app_id,
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            self.email,
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            self.user_id,
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            last_stream_ordering,
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            self.clock.time_msec(),
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        )
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        if not pusher_still_exists:
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            # The pusher has been deleted while we were processing, so
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            # lets just stop and return.
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            self.on_stop()
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    def seconds_until(self, ts_msec):
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        secs = (ts_msec - self.clock.time_msec()) / 1000
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        return max(secs, 0)
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    def get_room_throttle_ms(self, room_id):
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        if room_id in self.throttle_params:
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            return self.throttle_params[room_id]["throttle_ms"]
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        else:
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            return 0
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    def get_room_last_sent_ts(self, room_id):
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        if room_id in self.throttle_params:
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            return self.throttle_params[room_id]["last_sent_ts"]
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        else:
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            return 0
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    def room_ready_to_notify_at(self, room_id):
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        """
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        Determines whether throttling should prevent us from sending an email
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        for the given room
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        Returns: The timestamp when we are next allowed to send an email notif
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        for this room
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        """
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        last_sent_ts = self.get_room_last_sent_ts(room_id)
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        throttle_ms = self.get_room_throttle_ms(room_id)
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        may_send_at = last_sent_ts + throttle_ms
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        return may_send_at
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    async def sent_notif_update_throttle(self, room_id, notified_push_action):
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        # We have sent a notification, so update the throttle accordingly.
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        # If the event that triggered the notif happened more than
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        # THROTTLE_RESET_AFTER_MS after the previous one that triggered a
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        # notif, we release the throttle. Otherwise, the throttle is increased.
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        time_of_previous_notifs = await self.store.get_time_of_last_push_action_before(
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            notified_push_action["stream_ordering"]
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        )
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        time_of_this_notifs = notified_push_action["received_ts"]
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        if time_of_previous_notifs is not None and time_of_this_notifs is not None:
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            gap = time_of_this_notifs - time_of_previous_notifs
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        else:
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            # if we don't know the arrival time of one of the notifs (it was not
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            # stored prior to email notification code) then assume a gap of
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            # zero which will just not reset the throttle
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            gap = 0
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        current_throttle_ms = self.get_room_throttle_ms(room_id)
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        if gap > THROTTLE_RESET_AFTER_MS:
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            new_throttle_ms = THROTTLE_START_MS
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        else:
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            if current_throttle_ms == 0:
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                new_throttle_ms = THROTTLE_START_MS
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            else:
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                new_throttle_ms = min(
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                    current_throttle_ms * THROTTLE_MULTIPLIER, THROTTLE_MAX_MS
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                )
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        self.throttle_params[room_id] = {
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            "last_sent_ts": self.clock.time_msec(),
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            "throttle_ms": new_throttle_ms,
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        }
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        await self.store.set_throttle_params(
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            self.pusher_id, room_id, self.throttle_params[room_id]
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        )
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    async def send_notification(self, push_actions, reason):
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        logger.info("Sending notif email for user %r", self.user_id)
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        await self.mailer.send_notification_mail(
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            self.app_id, self.user_id, self.email, push_actions, reason
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        )
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