zulip/zerver/worker/queue_processors.py

# Documented in https://zulip.readthedocs.io/en/latest/subsystems/queuing.html
import base64
import copy
import datetime
import email
import email.policy
import logging
import os
import signal
import smtplib
import socket
import tempfile
import time
import urllib
from abc import ABC, abstractmethod
from collections import defaultdict, deque
from email.message import EmailMessage
from functools import wraps
from threading import Timer
from typing import (
    Any,
    Callable,
    Dict,
    List,
    Mapping,
    MutableSequence,
    Optional,
    Tuple,
    Type,
    TypeVar,
    cast,
)

import requests
import ujson
from django.conf import settings
from django.db import connection
from django.utils.timezone import now as timezone_now
from zulip_bots.lib import ExternalBotHandler, extract_query_without_mention

from zerver.context_processors import common_context
from zerver.lib.actions import (
    do_mark_stream_messages_as_read,
    do_send_confirmation_email,
    do_update_embedded_data,
    do_update_user_activity,
    do_update_user_activity_interval,
    do_update_user_presence,
    internal_send_private_message,
    notify_realm_export,
    render_incoming_message,
)
from zerver.lib.bot_lib import EmbeddedBotHandler, EmbeddedBotQuitException, get_bot_handler
from zerver.lib.context_managers import lockfile
from zerver.lib.db import reset_queries
from zerver.lib.digest import handle_digest_email
from zerver.lib.email_mirror import decode_stream_email_address, is_missed_message_address
from zerver.lib.email_mirror import process_message as mirror_email
from zerver.lib.email_mirror import rate_limit_mirror_by_realm
from zerver.lib.email_notifications import handle_missedmessage_emails
from zerver.lib.error_notify import do_report_error
from zerver.lib.exceptions import RateLimited
from zerver.lib.export import export_realm_wrapper
from zerver.lib.outgoing_webhook import do_rest_call, get_outgoing_webhook_service_handler
from zerver.lib.push_notifications import (
    clear_push_device_tokens,
    handle_push_notification,
    handle_remove_push_notification,
    initialize_push_notifications,
)
from zerver.lib.pysa import mark_sanitized
from zerver.lib.queue import SimpleQueueClient, retry_event
from zerver.lib.remote_server import PushNotificationBouncerRetryLaterError
from zerver.lib.send_email import (
    EmailNotDeliveredException,
    FromAddress,
    handle_send_email_format_changes,
    send_email_from_dict,
    send_future_email,
)
from zerver.lib.streams import access_stream_by_id
from zerver.lib.timestamp import timestamp_to_datetime
from zerver.lib.url_preview import preview as url_preview
from zerver.models import (
    Client,
    Message,
    PreregistrationUser,
    Realm,
    RealmAuditLog,
    UserMessage,
    UserProfile,
    flush_per_request_caches,
    get_bot_services,
    get_client,
    get_system_bot,
    get_user_profile_by_id,
)

logger = logging.getLogger(__name__)

class WorkerDeclarationException(Exception):
    pass

ConcreteQueueWorker = TypeVar('ConcreteQueueWorker', bound='QueueProcessingWorker')

def assign_queue(
        queue_name: str, enabled: bool=True, queue_type: str="consumer",
) -> Callable[[Type[ConcreteQueueWorker]], Type[ConcreteQueueWorker]]:
    def decorate(clazz: Type[ConcreteQueueWorker]) -> Type[ConcreteQueueWorker]:
        clazz.queue_name = queue_name
        if enabled:
            register_worker(queue_name, clazz, queue_type)
        return clazz
    return decorate

worker_classes: Dict[str, Type["QueueProcessingWorker"]] = {}
queues: Dict[str, Dict[str, Type["QueueProcessingWorker"]]] = {}
def register_worker(queue_name: str, clazz: Type['QueueProcessingWorker'], queue_type: str) -> None:
    if queue_type not in queues:
        queues[queue_type] = {}
    queues[queue_type][queue_name] = clazz
    worker_classes[queue_name] = clazz

def get_worker(queue_name: str) -> 'QueueProcessingWorker':
    return worker_classes[queue_name]()

def get_active_worker_queues(queue_type: Optional[str]=None) -> List[str]:
    """Returns all the non-test worker queues."""
    if queue_type is None:
        return list(worker_classes.keys())
    return list(queues[queue_type].keys())

def check_and_send_restart_signal() -> None:
    try:
        if not connection.is_usable():
            logging.warning("*** Sending self SIGUSR1 to trigger a restart.")
            os.kill(os.getpid(), signal.SIGUSR1)
    except Exception:
        pass

def retry_send_email_failures(
        func: Callable[[ConcreteQueueWorker, Dict[str, Any]], None],
) -> Callable[['QueueProcessingWorker', Dict[str, Any]], None]:

    @wraps(func)
    def wrapper(worker: ConcreteQueueWorker, data: Dict[str, Any]) -> None:
        try:
            func(worker, data)
        except (smtplib.SMTPServerDisconnected, socket.gaierror, EmailNotDeliveredException):
            def on_failure(event: Dict[str, Any]) -> None:
                logging.exception("Event %r failed", event)

            retry_event(worker.queue_name, data, on_failure)

    return wrapper

class QueueProcessingWorker(ABC):
    queue_name: str = None
    CONSUME_ITERATIONS_BEFORE_UPDATE_STATS_NUM = 50

    def __init__(self) -> None:
        self.q: SimpleQueueClient = None
        if self.queue_name is None:
            raise WorkerDeclarationException("Queue worker declared without queue_name")

        self.initialize_statistics()

    def initialize_statistics(self) -> None:
        self.queue_last_emptied_timestamp = time.time()
        self.consumed_since_last_emptied = 0
        self.recent_consume_times: MutableSequence[Tuple[int, float]] = deque(maxlen=50)
        self.consume_interation_counter = 0

        self.update_statistics(0)

    def update_statistics(self, remaining_queue_size: int) -> None:
        total_seconds = sum([seconds for _, seconds in self.recent_consume_times])
        total_events = sum([events_number for events_number, _ in self.recent_consume_times])
        if total_events == 0:
            recent_average_consume_time = None
        else:
            recent_average_consume_time = total_seconds / total_events
        stats_dict = dict(
            update_time=time.time(),
            recent_average_consume_time=recent_average_consume_time,
            current_queue_size=remaining_queue_size,
            queue_last_emptied_timestamp=self.queue_last_emptied_timestamp,
            consumed_since_last_emptied=self.consumed_since_last_emptied,
        )

        os.makedirs(settings.QUEUE_STATS_DIR, exist_ok=True)

        fname = f'{self.queue_name}.stats'
        fn = os.path.join(settings.QUEUE_STATS_DIR, fname)
        with lockfile(fn + '.lock'):
            tmp_fn = fn + '.tmp'
            with open(tmp_fn, 'w') as f:
                serialized_dict = ujson.dumps(stats_dict, indent=2)
                serialized_dict += '\n'
                f.write(serialized_dict)
            os.rename(tmp_fn, fn)

    @abstractmethod
    def consume(self, data: Dict[str, Any]) -> None:
        pass

    def do_consume(self, consume_func: Callable[[List[Dict[str, Any]]], None],
                   events: List[Dict[str, Any]]) -> None:
        try:
            time_start = time.time()
            consume_func(events)
            consume_time_seconds: Optional[float] = time.time() - time_start
            self.consumed_since_last_emptied += len(events)
        except Exception:
            self._handle_consume_exception(events)
            consume_time_seconds = None
        finally:
            flush_per_request_caches()
            reset_queries()

            if consume_time_seconds is not None:
                self.recent_consume_times.append((len(events), consume_time_seconds))

            if self.q is not None:
                remaining_queue_size = self.q.queue_size()
            else:
                remaining_queue_size = 0

            if remaining_queue_size == 0:
                self.queue_last_emptied_timestamp = time.time()
                self.consumed_since_last_emptied = 0

            self.consume_interation_counter += 1
            if self.consume_interation_counter >= self.CONSUME_ITERATIONS_BEFORE_UPDATE_STATS_NUM:

                self.consume_interation_counter = 0
                self.update_statistics(remaining_queue_size)

    def consume_wrapper(self, data: Dict[str, Any]) -> None:
        consume_func = lambda events: self.consume(events[0])
        self.do_consume(consume_func, [data])

    def _handle_consume_exception(self, events: List[Dict[str, Any]]) -> None:
        self._log_problem()
        if not os.path.exists(settings.QUEUE_ERROR_DIR):
            os.mkdir(settings.QUEUE_ERROR_DIR)  # nocoverage
        # Use 'mark_sanitized' to prevent Pysa from detecting this false positive
        # flow. 'queue_name' is always a constant string.
        fname = mark_sanitized(f'{self.queue_name}.errors')
        fn = os.path.join(settings.QUEUE_ERROR_DIR, fname)
        line = f'{time.asctime()}\t{ujson.dumps(events)}\n'
        lock_fn = fn + '.lock'
        with lockfile(lock_fn):
            with open(fn, 'ab') as f:
                f.write(line.encode('utf-8'))
        check_and_send_restart_signal()

    def _log_problem(self) -> None:
        logging.exception("Problem handling data on queue %s", self.queue_name)

    def setup(self) -> None:
        self.q = SimpleQueueClient()

    def start(self) -> None:
        self.initialize_statistics()
        self.q.register_json_consumer(self.queue_name, self.consume_wrapper)
        self.q.start_consuming()

    def stop(self) -> None:  # nocoverage
        self.q.stop_consuming()

class LoopQueueProcessingWorker(QueueProcessingWorker):
    sleep_delay = 0
    sleep_only_if_empty = True

    def start(self) -> None:  # nocoverage
        self.initialize_statistics()
        while True:
            events = self.q.json_drain_queue(self.queue_name)
            self.do_consume(self.consume_batch, events)
            # To avoid spinning the CPU, we go to sleep if there's
            # nothing in the queue, or for certain queues with
            # sleep_only_if_empty=False, unconditionally.
            if not self.sleep_only_if_empty or len(events) == 0:
                time.sleep(self.sleep_delay)

    @abstractmethod
    def consume_batch(self, events: List[Dict[str, Any]]) -> None:
        pass

    def consume(self, event: Dict[str, Any]) -> None:
        """In LoopQueueProcessingWorker, consume is used just for automated tests"""
        self.consume_batch([event])

@assign_queue('signups')
class SignupWorker(QueueProcessingWorker):
    def consume(self, data: Dict[str, Any]) -> None:
        # TODO: This is the only implementation with Dict cf Mapping; should we simplify?
        user_profile = get_user_profile_by_id(data['user_id'])
        logging.info(
            "Processing signup for user %s in realm %s",
            user_profile.id, user_profile.realm.string_id,
        )
        if settings.MAILCHIMP_API_KEY and settings.PRODUCTION:
            endpoint = "https://{}.api.mailchimp.com/3.0/lists/{}/members".format(
                settings.MAILCHIMP_API_KEY.split('-')[1], settings.ZULIP_FRIENDS_LIST_ID,
            )
            params = dict(data)
            del params['user_id']
            params['list_id'] = settings.ZULIP_FRIENDS_LIST_ID
            params['status'] = 'subscribed'
            r = requests.post(endpoint, auth=('apikey', settings.MAILCHIMP_API_KEY), json=params, timeout=10)
            if r.status_code == 400 and ujson.loads(r.text)['title'] == 'Member Exists':
                logging.warning("Attempted to sign up already existing email to list: %s",
                                data['email_address'])
            elif r.status_code == 400:
                retry_event(self.queue_name, data, lambda e: r.raise_for_status())
            else:
                r.raise_for_status()

@assign_queue('invites')
class ConfirmationEmailWorker(QueueProcessingWorker):
    def consume(self, data: Mapping[str, Any]) -> None:
        if "email" in data:
            # When upgrading from a version up through 1.7.1, there may be
            # existing items in the queue with `email` instead of `prereg_id`.
            invitee = PreregistrationUser.objects.filter(
                email__iexact=data["email"].strip()).latest("invited_at")
        else:
            invitee = PreregistrationUser.objects.filter(id=data["prereg_id"]).first()
            if invitee is None:
                # The invitation could have been revoked
                return

        referrer = get_user_profile_by_id(data["referrer_id"])
        logger.info("Sending invitation for realm %s to %s", referrer.realm.string_id, invitee.email)
        activate_url = do_send_confirmation_email(invitee, referrer)

        # queue invitation reminder
        if settings.INVITATION_LINK_VALIDITY_DAYS >= 4:
            context = common_context(referrer)
            context.update({
                'activate_url': activate_url,
                'referrer_name': referrer.full_name,
                'referrer_email': referrer.delivery_email,
                'referrer_realm_name': referrer.realm.name,
            })
            send_future_email(
                "zerver/emails/invitation_reminder",
                referrer.realm,
                to_emails=[invitee.email],
                from_address=FromAddress.tokenized_no_reply_placeholder,
                language=referrer.realm.default_language,
                context=context,
                delay=datetime.timedelta(days=settings.INVITATION_LINK_VALIDITY_DAYS - 2))

@assign_queue('user_activity', queue_type="loop")
class UserActivityWorker(LoopQueueProcessingWorker):
    """The UserActivity queue is perhaps our highest-traffic queue, and
    requires some care to ensure it performes adequately.

    We use a LoopQueueProcessingWorker as a performance optimization
    for managing the queue.  The structure of UserActivity records is
    such that they are easily deduplicated before being sent to the
    database; we take advantage of that to make this queue highly
    effective at dealing with a backlog containing many similar
    events.  Such a backlog happen in a few ways:

    * In abuse/DoS situations, if a client is sending huge numbers of
      similar requests to the server.
    * If the queue ends up with several minutes of backlog e.g. due to
      downtime of the queue processor, many clients will have several
      common events from doing an action multiple times.

    """
    sleep_delay = 10
    sleep_only_if_empty = True
    client_id_map: Dict[str, int] = {}

    def start(self) -> None:
        # For our unit tests to make sense, we need to clear this on startup.
        self.client_id_map = {}
        super().start()

    def consume_batch(self, user_activity_events: List[Dict[str, Any]]) -> None:
        uncommitted_events: Dict[Tuple[int, int, str], Tuple[int, float]] = {}

        # First, we drain the queue of all user_activity events and
        # deduplicate them for insertion into the database.
        for event in user_activity_events:
            user_profile_id = event["user_profile_id"]

            if "client_id" not in event:
                # This is for compatibility with older events still stuck in the queue,
                # that used the client name in event["client"] instead of having
                # event["client_id"] directly.
                # TODO: This can be deleted for release >= 2.3.
                if event["client"] not in self.client_id_map:
                    client = get_client(event["client"])
                    self.client_id_map[event["client"]] = client.id
                client_id = self.client_id_map[event["client"]]
            else:
                client_id = event["client_id"]

            key_tuple = (user_profile_id, client_id, event["query"])
            if key_tuple not in uncommitted_events:
                uncommitted_events[key_tuple] = (1, event['time'])
            else:
                count, time = uncommitted_events[key_tuple]
                uncommitted_events[key_tuple] = (count + 1, max(time, event['time']))

        # Then we insert the updates into the database.
        #
        # TODO: Doing these updates in sequence individually is likely
        # inefficient; the idealized version would do some sort of
        # bulk insert_or_update query.
        for key_tuple in uncommitted_events:
            (user_profile_id, client_id, query) = key_tuple
            count, time = uncommitted_events[key_tuple]
            log_time = timestamp_to_datetime(time)
            do_update_user_activity(user_profile_id, client_id, query, count, log_time)

@assign_queue('user_activity_interval')
class UserActivityIntervalWorker(QueueProcessingWorker):
    def consume(self, event: Mapping[str, Any]) -> None:
        user_profile = get_user_profile_by_id(event["user_profile_id"])
        log_time = timestamp_to_datetime(event["time"])
        do_update_user_activity_interval(user_profile, log_time)

@assign_queue('user_presence')
class UserPresenceWorker(QueueProcessingWorker):
    def consume(self, event: Mapping[str, Any]) -> None:
        logging.debug("Received presence event: %s", event)
        user_profile = get_user_profile_by_id(event["user_profile_id"])
        client = get_client(event["client"])
        log_time = timestamp_to_datetime(event["time"])
        status = event["status"]
        do_update_user_presence(user_profile, client, log_time, status)

@assign_queue('missedmessage_emails', queue_type="loop")
class MissedMessageWorker(QueueProcessingWorker):
    # Aggregate all messages received over the last BATCH_DURATION
    # seconds to let someone finish sending a batch of messages and/or
    # editing them before they are sent out as emails to recipients.
    #
    # The timer is running whenever; we poll at most every TIMER_FREQUENCY
    # seconds, to avoid excessive activity.
    #
    # TODO: Since this process keeps events in memory for up to 2
    # minutes, it now will lose approximately BATCH_DURATION worth of
    # missed_message emails whenever it is restarted as part of a
    # server restart.  We should probably add some sort of save/reload
    # mechanism for that case.
    TIMER_FREQUENCY = 5
    BATCH_DURATION = 120
    timer_event: Optional[Timer] = None
    events_by_recipient: Dict[int, List[Dict[str, Any]]] = defaultdict(list)
    batch_start_by_recipient: Dict[int, float] = {}

    def consume(self, event: Dict[str, Any]) -> None:
        logging.debug("Received missedmessage_emails event: %s", event)

        # When we process an event, just put it into the queue and ensure we have a timer going.
        user_profile_id = event['user_profile_id']
        if user_profile_id not in self.batch_start_by_recipient:
            self.batch_start_by_recipient[user_profile_id] = time.time()
        self.events_by_recipient[user_profile_id].append(event)

        self.ensure_timer()

    def ensure_timer(self) -> None:
        if self.timer_event is not None:
            return
        self.timer_event = Timer(self.TIMER_FREQUENCY, MissedMessageWorker.maybe_send_batched_emails, [self])
        self.timer_event.start()

    def stop_timer(self) -> None:
        if self.timer_event and self.timer_event.is_alive():
            self.timer_event.cancel()
            self.timer_event = None

    def maybe_send_batched_emails(self) -> None:
        self.stop_timer()

        current_time = time.time()
        for user_profile_id, timestamp in list(self.batch_start_by_recipient.items()):
            if current_time - timestamp < self.BATCH_DURATION:
                continue
            events = self.events_by_recipient[user_profile_id]
            logging.info("Batch-processing %s missedmessage_emails events for user %s",
                         len(events), user_profile_id)
            handle_missedmessage_emails(user_profile_id, events)
            del self.events_by_recipient[user_profile_id]
            del self.batch_start_by_recipient[user_profile_id]

        # By only restarting the timer if there are actually events in
        # the queue, we ensure this queue processor is idle when there
        # are no missed-message emails to process.
        if len(self.batch_start_by_recipient) > 0:
            self.ensure_timer()

@assign_queue('email_senders')
class EmailSendingWorker(QueueProcessingWorker):
    @retry_send_email_failures
    def consume(self, event: Dict[str, Any]) -> None:
        # Copy the event, so that we don't pass the `failed_tries'
        # data to send_email_from_dict (which neither takes that
        # argument nor needs that data).
        copied_event = copy.deepcopy(event)
        if 'failed_tries' in copied_event:
            del copied_event['failed_tries']
        handle_send_email_format_changes(copied_event)
        send_email_from_dict(copied_event)

@assign_queue('missedmessage_mobile_notifications')
class PushNotificationsWorker(QueueProcessingWorker):  # nocoverage
    def start(self) -> None:
        # initialize_push_notifications doesn't strictly do anything
        # beyond printing some logging warnings if push notifications
        # are not available in the current configuration.
        initialize_push_notifications()
        super().start()

    def consume(self, event: Dict[str, Any]) -> None:
        try:
            if event.get("type", "add") == "remove":
                message_ids = event.get('message_ids')
                if message_ids is None:  # legacy task across an upgrade
                    message_ids = [event['message_id']]
                handle_remove_push_notification(event['user_profile_id'], message_ids)
            else:
                handle_push_notification(event['user_profile_id'], event)
        except PushNotificationBouncerRetryLaterError:
            def failure_processor(event: Dict[str, Any]) -> None:
                logger.warning(
                    "Maximum retries exceeded for trigger:%s event:push_notification",
                    event['user_profile_id'])
            retry_event(self.queue_name, event, failure_processor)

@assign_queue('error_reports')
class ErrorReporter(QueueProcessingWorker):
    def consume(self, event: Mapping[str, Any]) -> None:
        logging.info("Processing traceback with type %s for %s", event['type'], event.get('user_email'))
        if settings.ERROR_REPORTING:
            do_report_error(event['report']['host'], event['type'], event['report'])

@assign_queue('digest_emails')
class DigestWorker(QueueProcessingWorker):  # nocoverage
    # Who gets a digest is entirely determined by the enqueue_digest_emails
    # management command, not here.
    def consume(self, event: Mapping[str, Any]) -> None:
        logging.info("Received digest event: %s", event)
        handle_digest_email(event["user_profile_id"], event["cutoff"])

@assign_queue('email_mirror')
class MirrorWorker(QueueProcessingWorker):
    def consume(self, event: Mapping[str, Any]) -> None:
        rcpt_to = event['rcpt_to']
        msg = email.message_from_bytes(
            base64.b64decode(event["msg_base64"]),
            policy=email.policy.default,
        )
        assert isinstance(msg, EmailMessage)  # https://github.com/python/typeshed/issues/2417
        if not is_missed_message_address(rcpt_to):
            # Missed message addresses are one-time use, so we don't need
            # to worry about emails to them resulting in message spam.
            recipient_realm = decode_stream_email_address(rcpt_to)[0].realm
            try:
                rate_limit_mirror_by_realm(recipient_realm)
            except RateLimited:
                logger.warning("MirrorWorker: Rejecting an email from: %s "
                               "to realm: %s - rate limited.",
                               msg['From'], recipient_realm.name)
                return

        mirror_email(msg, rcpt_to=rcpt_to)

@assign_queue('test', queue_type="test")
class TestWorker(QueueProcessingWorker):
    # This worker allows you to test the queue worker infrastructure without
    # creating significant side effects.  It can be useful in development or
    # for troubleshooting prod/staging.  It pulls a message off the test queue
    # and appends it to a file in /tmp.
    def consume(self, event: Mapping[str, Any]) -> None:  # nocoverage
        fn = settings.ZULIP_WORKER_TEST_FILE
        message = ujson.dumps(event)
        logging.info("TestWorker should append this message to %s: %s", fn, message)
        with open(fn, 'a') as f:
            f.write(message + '\n')

@assign_queue('embed_links')
class FetchLinksEmbedData(QueueProcessingWorker):
    def consume(self, event: Mapping[str, Any]) -> None:
        for url in event['urls']:
            start_time = time.time()
            url_preview.get_link_embed_data(url)
            logging.info("Time spent on get_link_embed_data for %s: %s", url, time.time() - start_time)

        message = Message.objects.get(id=event['message_id'])
        # If the message changed, we will run this task after updating the message
        # in zerver.views.messages.update_message_backend
        if message.content != event['message_content']:
            return
        if message.content is not None:
            query = UserMessage.objects.filter(
                message=message.id,
            )
            message_user_ids = set(query.values_list('user_profile_id', flat=True))

            # Fetch the realm whose settings we're using for rendering
            realm = Realm.objects.get(id=event['message_realm_id'])

            # If rendering fails, the called code will raise a JsonableError.
            rendered_content = render_incoming_message(
                message,
                message.content,
                message_user_ids,
                realm)
            do_update_embedded_data(
                message.sender, message, message.content, rendered_content)

@assign_queue('outgoing_webhooks')
class OutgoingWebhookWorker(QueueProcessingWorker):
    def consume(self, event: Mapping[str, Any]) -> None:
        message = event['message']
        dup_event = cast(Dict[str, Any], event)
        dup_event['command'] = message['content']

        services = get_bot_services(event['user_profile_id'])
        for service in services:
            dup_event['service_name'] = str(service.name)
            service_handler = get_outgoing_webhook_service_handler(service)
            request_data = service_handler.build_bot_request(dup_event)
            if request_data:
                do_rest_call(service.base_url,
                             request_data,
                             dup_event,
                             service_handler)

@assign_queue('embedded_bots')
class EmbeddedBotWorker(QueueProcessingWorker):

    def get_bot_api_client(self, user_profile: UserProfile) -> EmbeddedBotHandler:
        return EmbeddedBotHandler(user_profile)

    def consume(self, event: Mapping[str, Any]) -> None:
        user_profile_id = event['user_profile_id']
        user_profile = get_user_profile_by_id(user_profile_id)

        message = cast(Dict[str, Any], event['message'])

        # TODO: Do we actually want to allow multiple Services per bot user?
        services = get_bot_services(user_profile_id)
        for service in services:
            bot_handler = get_bot_handler(str(service.name))
            if bot_handler is None:
                logging.error(
                    "Error: User %s has bot with invalid embedded bot service %s",
                    user_profile_id, service.name,
                )
                continue
            try:
                if hasattr(bot_handler, 'initialize'):
                    bot_handler.initialize(self.get_bot_api_client(user_profile))
                if event['trigger'] == 'mention':
                    message['content'] = extract_query_without_mention(
                        message=message,
                        client=cast(ExternalBotHandler, self.get_bot_api_client(user_profile)),
                    )
                    assert message['content'] is not None
                bot_handler.handle_message(
                    message=message,
                    bot_handler=self.get_bot_api_client(user_profile),
                )
            except EmbeddedBotQuitException as e:
                logging.warning(str(e))

@assign_queue('deferred_work')
class DeferredWorker(QueueProcessingWorker):
    def consume(self, event: Dict[str, Any]) -> None:
        if event['type'] == 'mark_stream_messages_as_read':
            user_profile = get_user_profile_by_id(event['user_profile_id'])
            client = Client.objects.get(id=event['client_id'])

            for stream_id in event['stream_ids']:
                # Since the user just unsubscribed, we don't require
                # an active Subscription object (otherwise, private
                # streams would never be accessible)
                (stream, recipient, sub) = access_stream_by_id(user_profile, stream_id,
                                                               require_active=False)
                do_mark_stream_messages_as_read(user_profile, client, stream)
        elif event['type'] == 'clear_push_device_tokens':
            try:
                clear_push_device_tokens(event["user_profile_id"])
            except PushNotificationBouncerRetryLaterError:
                def failure_processor(event: Dict[str, Any]) -> None:
                    logger.warning(
                        "Maximum retries exceeded for trigger:%s event:clear_push_device_tokens",
                        event['user_profile_id'])
                retry_event(self.queue_name, event, failure_processor)
        elif event['type'] == 'realm_export':
            start = time.time()
            realm = Realm.objects.get(id=event['realm_id'])
            output_dir = tempfile.mkdtemp(prefix="zulip-export-")
            export_event = RealmAuditLog.objects.get(id=event['id'])
            user_profile = get_user_profile_by_id(event['user_profile_id'])

            try:
                public_url = export_realm_wrapper(realm=realm, output_dir=output_dir,
                                                  threads=6, upload=True, public_only=True,
                                                  delete_after_upload=True)
            except Exception:
                export_event.extra_data = ujson.dumps(dict(
                    failed_timestamp=timezone_now().timestamp(),
                ))
                export_event.save(update_fields=['extra_data'])
                logging.error(
                    "Data export for %s failed after %s",
                    user_profile.realm.string_id, time.time() - start,
                )
                notify_realm_export(user_profile)
                return

            assert public_url is not None

            # Update the extra_data field now that the export is complete.
            export_event.extra_data = ujson.dumps(dict(
                export_path=urllib.parse.urlparse(public_url).path,
            ))
            export_event.save(update_fields=['extra_data'])

            # Send a private message notification letting the user who
            # triggered the export know the export finished.
            content = f"Your data export is complete and has been uploaded here:\n\n{public_url}"
            internal_send_private_message(
                realm=user_profile.realm,
                sender=get_system_bot(settings.NOTIFICATION_BOT),
                recipient_user=user_profile,
                content=content,
            )

            # For future frontend use, also notify administrator
            # clients that the export happened.
            notify_realm_export(user_profile)
            logging.info(
                "Completed data export for %s in %s",
                user_profile.realm.string_id, time.time() - start,
            )