wip: indexer recover from connection errors

Author: aaxelb

share/search/daemon.py

@@ -1,13 +1,16 @@
 import contextlib
 import collections
+from collections.abc import Callable
 import dataclasses
 import logging
 import queue
 import random
 import threading
 import time
 
+import amqp.exceptions
 from django.conf import settings
+import kombu
 from kombu.mixins import ConsumerMixin
 import sentry_sdk
 
@@ -27,6 +30,7 @@
 MINIMUM_BACKOFF_FACTOR = 1.6    # unitless ratio
 MAXIMUM_BACKOFF_FACTOR = 2.0    # unitless ratio
 MAXIMUM_BACKOFF_TIMEOUT = 60    # seconds
+CONNECTION_HEARTBEAT = 20       # seconds
 
 
 class TooFastSlowDown(Exception):
@@ -35,7 +39,10 @@ class TooFastSlowDown(Exception):
 
 class IndexerDaemonControl:
     def __init__(self, celery_app, *, daemonthread_context=None, stop_event=None):
-        self.celery_app = celery_app
+        self.kombu_connection = kombu.Connection(
+            celery_app.conf.broker_url,  # use celery_app.conf for consistent config
+            heartbeat=CONNECTION_HEARTBEAT,
+        )
         self.daemonthread_context = daemonthread_context
         self._daemonthreads = []
         # shared stop_event for all threads below
@@ -50,10 +57,16 @@ def start_daemonthreads_for_strategy(self, index_strategy):
         )
         # spin up daemonthreads, ready for messages
         self._daemonthreads.extend(_daemon.start())
-        # assign a thread to pass messages to this daemon
-        threading.Thread(
-            target=CeleryMessageConsumer(self.celery_app, _daemon).run,
-        ).start()
+        _consumer = KombuMessageConsumer(
+            kombu_connection=self.kombu_connection.clone(),
+            stop_event=self.stop_event,
+            index_strategy=index_strategy,
+            message_callback=_daemon.on_message,
+        )
+        # give the daemon direct access to the connection, for acking purposes
+        _daemon.ack_callback = _consumer.ensure_ack
+        # assign a thread for the consumer to receive and enqueue messages to this daemon
+        threading.Thread(target=_consumer.run).start()
         return _daemon
 
     def start_all_daemonthreads(self):
@@ -67,18 +80,16 @@ def stop_daemonthreads(self, *, wait=False):
                 _thread.join()
 
 
-class CeleryMessageConsumer(ConsumerMixin):
+class KombuMessageConsumer(ConsumerMixin):
     PREFETCH_COUNT = 7500
 
-    # (from ConsumerMixin)
-    # should_stop: bool
+    should_stop: bool  # (from ConsumerMixin)
 
-    def __init__(self, celery_app, indexer_daemon):
-        self.connection = celery_app.pool.acquire(block=True)
-        self.celery_app = celery_app
-        self.__stop_event = indexer_daemon.stop_event
-        self.__message_callback = indexer_daemon.on_message
-        self.__index_strategy = indexer_daemon.index_strategy
+    def __init__(self, *, kombu_connection, stop_event, message_callback, index_strategy):
+        self.connection = kombu_connection
+        self.__stop_event = stop_event
+        self.__message_callback = message_callback
+        self.__index_strategy = index_strategy
 
     # overrides ConsumerMixin.run
     def run(self):
@@ -112,9 +123,35 @@ def get_consumers(self, Consumer, channel):
     def __repr__(self):
         return '<{}({})>'.format(self.__class__.__name__, self.__index_strategy.name)
 
+    def consume(self, *args, **kwargs):
+        # wrap `consume` in `kombu.Connection.ensure`, following guidance from
+        # https://docs.celeryq.dev/projects/kombu/en/stable/userguide/failover.html#consumer
+        consume = self.connection.ensure(self.connection, super().consume)
+        return consume(*args, **kwargs)
+
+    def ensure_ack(self, daemon_message: messages.DaemonMessage):
+        # if the connection the message came thru is no longer usable,
+        # use `kombu.Connection.autoretry` and `kombu.Channel.basic_ack`
+        # to ensure the ack goes thru
+        try:
+            daemon_message.ack()
+        except (ConnectionError, amqp.exceptions.ConnectionError):
+            @self.connection.autoretry
+            def _do_ack(*, channel):
+                try:
+                    channel.basic_ack(daemon_message.kombu_message.delivery_tag)
+                finally:
+                    channel.close()
+            _do_ack()
+
+
+def _default_ack_callback(daemon_message: messages.DaemonMessage) -> None:
+    daemon_message.ack()
+
 
 class IndexerDaemon:
     MAX_LOCAL_QUEUE_SIZE = 5000
+    ack_callback: Callable[[messages.DaemonMessage], None] = _default_ack_callback
 
     def __init__(self, index_strategy, *, stop_event=None, daemonthread_context=None):
         self.stop_event = (
@@ -154,6 +191,7 @@ def start_typed_loop_and_queue(self, message_type) -> threading.Thread:
             local_message_queue=_queue_from_rabbit_to_daemon,
             log_prefix=f'{repr(self)} MessageHandlingLoop: ',
             daemonthread_context=self.__daemonthread_context,
+            ack_callback=self.ack_callback,
         )
         return _handling_loop.start_thread()
 
@@ -186,7 +224,8 @@ class MessageHandlingLoop:
     stop_event: threading.Event
     local_message_queue: queue.Queue
     log_prefix: str
-    daemonthread_context: contextlib.AbstractContextManager
+    daemonthread_context: Callable[[], contextlib.AbstractContextManager]
+    ack_callback: Callable[[messages.DaemonMessage], None]
     _leftover_daemon_messages_by_target_id = None
 
     def __post_init__(self):
@@ -270,7 +309,7 @@ def _handle_some_messages(self):
                     sentry_sdk.capture_message('error handling message', extras={'message_response': message_response})
                 target_id = message_response.index_message.target_id
                 for daemon_message in daemon_messages_by_target_id.pop(target_id, ()):
-                    daemon_message.ack()  # finally set it free
+                    self.ack_callback(daemon_message)
             if daemon_messages_by_target_id:  # should be empty by now
                 logger.error('%sUnhandled messages?? %s', self.log_prefix, len(daemon_messages_by_target_id))
                 sentry_sdk.capture_message(