zulip/zerver/lib/queue.py

from django.conf import settings
import pika
from pika.adapters.blocking_connection import BlockingChannel
from pika.spec import Basic
import logging
import ujson
import random
import time
import threading
from collections import defaultdict

from zerver.lib.utils import statsd
from typing import Any, Callable, Dict, List, Mapping, Optional, Set, Union

MAX_REQUEST_RETRIES = 3
Consumer = Callable[[BlockingChannel, Basic.Deliver, pika.BasicProperties, str], None]

# This simple queuing library doesn't expose much of the power of
# rabbitmq/pika's queuing system; its purpose is to just provide an
# interface for external files to put things into queues and take them
# out from bots without having to import pika code all over our codebase.
class SimpleQueueClient:
    def __init__(self) -> None:
        self.log = logging.getLogger('zulip.queue')
        self.queues = set()  # type: Set[str]
        self.channel = None  # type: Optional[BlockingChannel]
        self.consumers = defaultdict(set)  # type: Dict[str, Set[Consumer]]
        # Disable RabbitMQ heartbeats since BlockingConnection can't process them
        self.rabbitmq_heartbeat = 0  # type: Optional[int]
        self._connect()

    def _connect(self) -> None:
        start = time.time()
        self.connection = pika.BlockingConnection(self._get_parameters())
        self.channel    = self.connection.channel()
        self.log.info('SimpleQueueClient connected (connecting took %.3fs)' % (time.time() - start,))

    def _reconnect(self) -> None:
        self.connection = None
        self.channel = None
        self.queues = set()
        self._connect()

    def _get_parameters(self) -> pika.ConnectionParameters:
        # We explicitly disable the RabbitMQ heartbeat feature, since
        # it doesn't make sense with BlockingConnection
        credentials = pika.PlainCredentials(settings.RABBITMQ_USERNAME,
                                            settings.RABBITMQ_PASSWORD)
        return pika.ConnectionParameters(settings.RABBITMQ_HOST,
                                         heartbeat_interval=self.rabbitmq_heartbeat,
                                         credentials=credentials)

    def _generate_ctag(self, queue_name: str) -> str:
        return "%s_%s" % (queue_name, str(random.getrandbits(16)))

    def _reconnect_consumer_callback(self, queue: str, consumer: Consumer) -> None:
        self.log.info("Queue reconnecting saved consumer %s to queue %s" % (consumer, queue))
        self.ensure_queue(queue, lambda: self.channel.basic_consume(consumer,
                                                                    queue=queue,
                                                                    consumer_tag=self._generate_ctag(queue)))

    def _reconnect_consumer_callbacks(self) -> None:
        for queue, consumers in self.consumers.items():
            for consumer in consumers:
                self._reconnect_consumer_callback(queue, consumer)

    def close(self) -> None:
        if self.connection:
            self.connection.close()

    def ready(self) -> bool:
        return self.channel is not None

    def ensure_queue(self, queue_name: str, callback: Callable[[], None]) -> None:
        '''Ensure that a given queue has been declared, and then call
           the callback with no arguments.'''
        if self.connection is None or not self.connection.is_open:
            self._connect()

        if queue_name not in self.queues:
            self.channel.queue_declare(queue=queue_name, durable=True)
            self.queues.add(queue_name)
        callback()

    def publish(self, queue_name: str, body: str) -> None:
        def do_publish() -> None:
            self.channel.basic_publish(
                exchange='',
                routing_key=queue_name,
                properties=pika.BasicProperties(delivery_mode=2),
                body=body)

            statsd.incr("rabbitmq.publish.%s" % (queue_name,))

        self.ensure_queue(queue_name, do_publish)

    def json_publish(self, queue_name: str, body: Union[Mapping[str, Any], str]) -> None:
        # Union because of zerver.middleware.write_log_line uses a str
        try:
            self.publish(queue_name, ujson.dumps(body))
            return
        except pika.exceptions.AMQPConnectionError:
            self.log.warning("Failed to send to rabbitmq, trying to reconnect and send again")

        self._reconnect()
        self.publish(queue_name, ujson.dumps(body))

    def register_consumer(self, queue_name: str, consumer: Consumer) -> None:
        def wrapped_consumer(ch: BlockingChannel,
                             method: Basic.Deliver,
                             properties: pika.BasicProperties,
                             body: str) -> None:
            try:
                consumer(ch, method, properties, body)
                ch.basic_ack(delivery_tag=method.delivery_tag)
            except Exception as e:
                ch.basic_nack(delivery_tag=method.delivery_tag)
                raise e

        self.consumers[queue_name].add(wrapped_consumer)
        self.ensure_queue(queue_name,
                          lambda: self.channel.basic_consume(wrapped_consumer, queue=queue_name,
                                                             consumer_tag=self._generate_ctag(queue_name)))

    def register_json_consumer(self, queue_name: str,
                               callback: Callable[[Dict[str, Any]], None]) -> None:
        def wrapped_callback(ch: BlockingChannel,
                             method: Basic.Deliver,
                             properties: pika.BasicProperties,
                             body: str) -> None:
            callback(ujson.loads(body))
        self.register_consumer(queue_name, wrapped_callback)

    def drain_queue(self, queue_name: str, json: bool=False) -> List[Dict[str, Any]]:
        "Returns all messages in the desired queue"
        messages = []

        def opened() -> None:
            while True:
                (meta, _, message) = self.channel.basic_get(queue_name)

                if not message:
                    break

                self.channel.basic_ack(meta.delivery_tag)
                if json:
                    message = ujson.loads(message)
                messages.append(message)

        self.ensure_queue(queue_name, opened)
        return messages

    def start_consuming(self) -> None:
        self.channel.start_consuming()

    def stop_consuming(self) -> None:
        self.channel.stop_consuming()

# Patch pika.adapters.TornadoConnection so that a socket error doesn't
# throw an exception and disconnect the tornado process from the rabbitmq
# queue. Instead, just re-connect as usual
class ExceptionFreeTornadoConnection(pika.adapters.TornadoConnection):
    def _adapter_disconnect(self) -> None:
        try:
            super()._adapter_disconnect()
        except (pika.exceptions.ProbableAuthenticationError,
                pika.exceptions.ProbableAccessDeniedError,
                pika.exceptions.IncompatibleProtocolError) as e:
            logging.warning("Caught exception '%r' in ExceptionFreeTornadoConnection when \
calling _adapter_disconnect, ignoring" % (e,))


class TornadoQueueClient(SimpleQueueClient):
    # Based on:
    # https://pika.readthedocs.io/en/0.9.8/examples/asynchronous_consumer_example.html
    def __init__(self) -> None:
        super().__init__()
        # Enable rabbitmq heartbeat since TornadoConection can process them
        self.rabbitmq_heartbeat = None
        self._on_open_cbs = []  # type: List[Callable[[], None]]

    def _connect(self, on_open_cb: Optional[Callable[[], None]]=None) -> None:
        self.log.info("Beginning TornadoQueueClient connection")
        if on_open_cb is not None:
            self._on_open_cbs.append(on_open_cb)
        self.connection = ExceptionFreeTornadoConnection(
            self._get_parameters(),
            on_open_callback = self._on_open,
            stop_ioloop_on_close = False)
        self.connection.add_on_close_callback(self._on_connection_closed)

    def _reconnect(self) -> None:
        self.connection = None
        self.channel = None
        self.queues = set()
        self._connect()

    def _on_open(self, connection: pika.connection.Connection) -> None:
        self.connection.channel(
            on_open_callback = self._on_channel_open)

    def _on_channel_open(self, channel: BlockingChannel) -> None:
        self.channel = channel
        for callback in self._on_open_cbs:
            callback()
        self._reconnect_consumer_callbacks()
        self.log.info('TornadoQueueClient connected')

    def _on_connection_closed(self, connection: pika.connection.Connection,
                              reply_code: int, reply_text: str) -> None:
        self.log.warning("TornadoQueueClient lost connection to RabbitMQ, reconnecting...")
        from tornado import ioloop

        # Try to reconnect in two seconds
        retry_seconds = 2

        def on_timeout() -> None:
            try:
                self._reconnect()
            except pika.exceptions.AMQPConnectionError:
                self.log.critical("Failed to reconnect to RabbitMQ, retrying...")
                ioloop.IOLoop.instance().add_timeout(time.time() + retry_seconds, on_timeout)

        ioloop.IOLoop.instance().add_timeout(time.time() + retry_seconds, on_timeout)

    def ensure_queue(self, queue_name: str, callback: Callable[[], None]) -> None:
        def finish(frame: Any) -> None:
            self.queues.add(queue_name)
            callback()

        if queue_name not in self.queues:
            # If we're not connected yet, send this message
            # once we have created the channel
            if not self.ready():
                self._on_open_cbs.append(lambda: self.ensure_queue(queue_name, callback))
                return

            self.channel.queue_declare(queue=queue_name, durable=True, callback=finish)
        else:
            callback()

    def register_consumer(self, queue_name: str, consumer: Consumer) -> None:
        def wrapped_consumer(ch: BlockingChannel,
                             method: Basic.Deliver,
                             properties: pika.BasicProperties,
                             body: str) -> None:
            consumer(ch, method, properties, body)
            ch.basic_ack(delivery_tag=method.delivery_tag)

        if not self.ready():
            self.consumers[queue_name].add(wrapped_consumer)
            return

        self.consumers[queue_name].add(wrapped_consumer)
        self.ensure_queue(queue_name,
                          lambda: self.channel.basic_consume(wrapped_consumer, queue=queue_name,
                                                             consumer_tag=self._generate_ctag(queue_name)))

queue_client = None  # type: Optional[SimpleQueueClient]
def get_queue_client() -> SimpleQueueClient:
    global queue_client
    if queue_client is None:
        if settings.RUNNING_INSIDE_TORNADO and settings.USING_RABBITMQ:
            queue_client = TornadoQueueClient()
        elif settings.USING_RABBITMQ:
            queue_client = SimpleQueueClient()

    return queue_client

# We using a simple lock to prevent multiple RabbitMQ messages being
# sent to the SimpleQueueClient at the same time; this is a workaround
# for an issue with the pika BlockingConnection where using
# BlockingConnection for multiple queues causes the channel to
# randomly close.
queue_lock = threading.RLock()

def queue_json_publish(queue_name: str,
                       event: Union[Dict[str, Any], str],
                       processor: Callable[[Any], None],
                       call_consume_in_tests: bool=False) -> None:
    # most events are dicts, but zerver.middleware.write_log_line uses a str
    with queue_lock:
        if settings.USING_RABBITMQ:
            get_queue_client().json_publish(queue_name, event)
        elif call_consume_in_tests:
            # Must be imported here: A top section import leads to obscure not-defined-ish errors.
            from zerver.worker.queue_processors import get_worker
            get_worker(queue_name).consume_wrapper(event)  # type: ignore # https://github.com/python/mypy/issues/3360
        else:
            processor(event)

def retry_event(queue_name: str,
                event: Dict[str, Any],
                failure_processor: Callable[[Dict[str, Any]], None]) -> None:
    if 'failed_tries' not in event:
        event['failed_tries'] = 0
    event['failed_tries'] += 1
    if event['failed_tries'] > MAX_REQUEST_RETRIES:
        failure_processor(event)
    else:
        queue_json_publish(queue_name, event, lambda x: None)