Merge pull request #759 from matrix-org/dbkr/email_notifs

Send email notifications for missed messages

1 files changed, 251 insertions, 0 deletions

diff --git a/synapse/push/emailpusher.py b/synapse/push/emailpusher.py
new file mode 100644
index 0000000000..3a13c7485a
--- /dev/null
+++ b/synapse/push/emailpusher.py
@@ -0,0 +1,251 @@
+# -*- coding: utf-8 -*-
+# Copyright 2016 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from twisted.internet import defer, reactor
+
+import logging
+
+from synapse.util.metrics import Measure
+from synapse.util.logcontext import LoggingContext
+
+from mailer import Mailer
+
+logger = logging.getLogger(__name__)
+
+# The amount of time we always wait before ever emailing about a notification
+# (to give the user a chance to respond to other push or notice the window)
+DELAY_BEFORE_MAIL_MS = 2 * 60 * 1000
+
+THROTTLE_START_MS = 2 * 60 * 1000
+THROTTLE_MAX_MS = (2 * 60 * 1000) * (2 ** 11)  # ~3 days
+THROTTLE_MULTIPLIER = 2
+
+# If no event triggers a notification for this long after the previous,
+# the throttle is released.
+THROTTLE_RESET_AFTER_MS = (2 * 60 * 1000) * (2 ** 11)  # ~3 days
+
+
+class EmailPusher(object):
+    """
+    A pusher that sends email notifications about events (approximately)
+    when they happen.
+    This shares quite a bit of code with httpusher: it would be good to
+    factor out the common parts
+    """
+    def __init__(self, hs, pusherdict):
+        self.hs = hs
+        self.store = self.hs.get_datastore()
+        self.clock = self.hs.get_clock()
+        self.pusher_id = pusherdict['id']
+        self.user_id = pusherdict['user_name']
+        self.app_id = pusherdict['app_id']
+        self.email = pusherdict['pushkey']
+        self.last_stream_ordering = pusherdict['last_stream_ordering']
+        self.timed_call = None
+        self.throttle_params = None
+
+        # See httppusher
+        self.max_stream_ordering = None
+
+        self.processing = False
+
+        if self.hs.config.email_enable_notifs:
+            self.mailer = Mailer(self.hs)
+        else:
+            self.mailer = None
+
+    @defer.inlineCallbacks
+    def on_started(self):
+        if self.mailer is not None:
+            self.throttle_params = yield self.store.get_throttle_params_by_room(
+                self.pusher_id
+            )
+            yield self._process()
+
+    def on_stop(self):
+        if self.timed_call:
+            self.timed_call.cancel()
+
+    @defer.inlineCallbacks
+    def on_new_notifications(self, min_stream_ordering, max_stream_ordering):
+        self.max_stream_ordering = max(max_stream_ordering, self.max_stream_ordering)
+        yield self._process()
+
+    def on_new_receipts(self, min_stream_id, max_stream_id):
+        # We could wake up and cancel the timer but there tend to be quite a
+        # lot of read receipts so it's probably less work to just let the
+        # timer fire
+        return defer.succeed(None)
+
+    @defer.inlineCallbacks
+    def on_timer(self):
+        self.timed_call = None
+        yield self._process()
+
+    @defer.inlineCallbacks
+    def _process(self):
+        if self.processing:
+            return
+
+        with LoggingContext("emailpush._process"):
+            with Measure(self.clock, "emailpush._process"):
+                try:
+                    self.processing = True
+                    # if the max ordering changes while we're running _unsafe_process,
+                    # call it again, and so on until we've caught up.
+                    while True:
+                        starting_max_ordering = self.max_stream_ordering
+                        try:
+                            yield self._unsafe_process()
+                        except:
+                            logger.exception("Exception processing notifs")
+                        if self.max_stream_ordering == starting_max_ordering:
+                            break
+                finally:
+                    self.processing = False
+
+    @defer.inlineCallbacks
+    def _unsafe_process(self):
+        """
+        Main logic of the push loop without the wrapper function that sets
+        up logging, measures and guards against multiple instances of it
+        being run.
+        """
+        unprocessed = yield self.store.get_unread_push_actions_for_user_in_range(
+            self.user_id, self.last_stream_ordering, self.max_stream_ordering
+        )
+
+        soonest_due_at = None
+
+        for push_action in unprocessed:
+            received_at = push_action['received_ts']
+            if received_at is None:
+                received_at = 0
+            notif_ready_at = received_at + DELAY_BEFORE_MAIL_MS
+
+            room_ready_at = self.room_ready_to_notify_at(
+                push_action['room_id']
+            )
+
+            should_notify_at = max(notif_ready_at, room_ready_at)
+
+            if should_notify_at < self.clock.time_msec():
+                # one of our notifications is ready for sending, so we send
+                # *one* email updating the user on their notifications,
+                # we then consider all previously outstanding notifications
+                # to be delivered.
+                yield self.send_notification(unprocessed)
+
+                yield self.save_last_stream_ordering_and_success(max([
+                    ea['stream_ordering'] for ea in unprocessed
+                ]))
+                yield self.sent_notif_update_throttle(
+                    push_action['room_id'], push_action
+                )
+                break
+            else:
+                if soonest_due_at is None or should_notify_at < soonest_due_at:
+                    soonest_due_at = should_notify_at
+
+                if self.timed_call is not None:
+                    self.timed_call.cancel()
+                    self.timed_call = None
+
+        if soonest_due_at is not None:
+            self.timed_call = reactor.callLater(
+                self.seconds_until(soonest_due_at), self.on_timer
+            )
+
+    @defer.inlineCallbacks
+    def save_last_stream_ordering_and_success(self, last_stream_ordering):
+        self.last_stream_ordering = last_stream_ordering
+        yield self.store.update_pusher_last_stream_ordering_and_success(
+            self.app_id, self.email, self.user_id,
+            last_stream_ordering, self.clock.time_msec()
+        )
+
+    def seconds_until(self, ts_msec):
+        return (ts_msec - self.clock.time_msec()) / 1000
+
+    def get_room_throttle_ms(self, room_id):
+        if room_id in self.throttle_params:
+            return self.throttle_params[room_id]["throttle_ms"]
+        else:
+            return 0
+
+    def get_room_last_sent_ts(self, room_id):
+        if room_id in self.throttle_params:
+            return self.throttle_params[room_id]["last_sent_ts"]
+        else:
+            return 0
+
+    def room_ready_to_notify_at(self, room_id):
+        """
+        Determines whether throttling should prevent us from sending an email
+        for the given room
+        Returns: True if we should send, False if we should not
+        """
+        last_sent_ts = self.get_room_last_sent_ts(room_id)
+        throttle_ms = self.get_room_throttle_ms(room_id)
+
+        may_send_at = last_sent_ts + throttle_ms
+        return may_send_at
+
+    @defer.inlineCallbacks
+    def sent_notif_update_throttle(self, room_id, notified_push_action):
+        # We have sent a notification, so update the throttle accordingly.
+        # If the event that triggered the notif happened more than
+        # THROTTLE_RESET_AFTER_MS after the previous one that triggered a
+        # notif, we release the throttle. Otherwise, the throttle is increased.
+        time_of_previous_notifs = yield self.store.get_time_of_last_push_action_before(
+            notified_push_action['stream_ordering']
+        )
+
+        time_of_this_notifs = notified_push_action['received_ts']
+
+        if time_of_previous_notifs is not None and time_of_this_notifs is not None:
+            gap = time_of_this_notifs - time_of_previous_notifs
+        else:
+            # if we don't know the arrival time of one of the notifs (it was not
+            # stored prior to email notification code) then assume a gap of
+            # zero which will just not reset the throttle
+            gap = 0
+
+        current_throttle_ms = self.get_room_throttle_ms(room_id)
+
+        if gap > THROTTLE_RESET_AFTER_MS:
+            new_throttle_ms = THROTTLE_START_MS
+        else:
+            if current_throttle_ms == 0:
+                new_throttle_ms = THROTTLE_START_MS
+            else:
+                new_throttle_ms = min(
+                    current_throttle_ms * THROTTLE_MULTIPLIER,
+                    THROTTLE_MAX_MS
+                )
+        self.throttle_params[room_id] = {
+            "last_sent_ts": self.clock.time_msec(),
+            "throttle_ms": new_throttle_ms
+        }
+        yield self.store.set_throttle_params(
+            self.pusher_id, room_id, self.throttle_params[room_id]
+        )
+
+    @defer.inlineCallbacks
+    def send_notification(self, push_actions):
+        logger.info("Sending notif email for user %r", self.user_id)
+        yield self.mailer.send_notification_mail(
+            self.user_id, self.email, push_actions
+        )