queue: Split common part of SimpleQueueClient into new base class.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

zerver/lib/queue.py

@@ -2,6 +2,7 @@ import logging
 import random
 import threading
 import time
+from abc import ABCMeta, abstractmethod
 from collections import defaultdict
 from typing import Any, Callable, Dict, List, Mapping, Optional, Set
 
@@ -22,7 +23,7 @@ Consumer = Callable[[BlockingChannel, Basic.Deliver, pika.BasicProperties, bytes
 # 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:
+class QueueClient(metaclass=ABCMeta):
     def __init__(
         self,
         # Disable RabbitMQ heartbeats by default because BlockingConnection can't process them
@@ -36,17 +37,13 @@ class SimpleQueueClient:
         self.is_consuming = False
         self._connect()
 
+    @abstractmethod
     def _connect(self) -> None:
-        start = time.time()
-        self.connection = pika.BlockingConnection(self._get_parameters())
-        self.channel = self.connection.channel()
-        self.log.info(f"SimpleQueueClient connected (connecting took {time.time() - start:.3f}s)")
+        raise NotImplementedError
 
+    @abstractmethod
     def _reconnect(self) -> None:
-        self.connection = None
-        self.channel = None
-        self.queues = set()
-        self._connect()
+        raise NotImplementedError
 
     def _get_parameters(self) -> pika.ConnectionParameters:
         credentials = pika.PlainCredentials(settings.RABBITMQ_USERNAME, settings.RABBITMQ_PASSWORD)
@@ -97,24 +94,12 @@ class SimpleQueueClient:
             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
 
+    @abstractmethod
     def ensure_queue(self, queue_name: str, callback: Callable[[BlockingChannel], 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()
-
-        assert self.channel is not None
-        if queue_name not in self.queues:
-            self.channel.queue_declare(queue=queue_name, durable=True)
-            self.queues.add(queue_name)
-        callback(self.channel)
+        raise NotImplementedError
 
     def publish(self, queue_name: str, body: bytes) -> None:
         def do_publish(channel: BlockingChannel) -> None:
@@ -140,6 +125,36 @@ class SimpleQueueClient:
         self._reconnect()
         self.publish(queue_name, data)
 
+
+class SimpleQueueClient(QueueClient):
+    def _connect(self) -> None:
+        start = time.time()
+        self.connection = pika.BlockingConnection(self._get_parameters())
+        self.channel = self.connection.channel()
+        self.log.info(f"SimpleQueueClient connected (connecting took {time.time() - start:.3f}s)")
+
+    def _reconnect(self) -> None:
+        self.connection = None
+        self.channel = None
+        self.queues = set()
+        self._connect()
+
+    def close(self) -> None:
+        if self.connection is not None:
+            self.connection.close()
+
+    def ensure_queue(self, queue_name: str, callback: Callable[[BlockingChannel], 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()
+
+        assert self.channel is not None
+        if queue_name not in self.queues:
+            self.channel.queue_declare(queue=queue_name, durable=True)
+            self.queues.add(queue_name)
+        callback(self.channel)
+
     def start_json_consumer(
         self,
         queue_name: str,

zerver/tests/test_queue.py

@@ -13,8 +13,8 @@ class TestTornadoQueueClient(ZulipTestCase):
     @mock.patch("zerver.lib.queue.ExceptionFreeTornadoConnection", autospec=True)
     def test_on_open_closed(self, mock_cxn: mock.MagicMock) -> None:
         with self.assertLogs("zulip.queue", "WARNING") as m:
+            mock_cxn().channel.side_effect = ConnectionClosed("500", "test")
             connection = TornadoQueueClient()
-            connection.connection.channel.side_effect = ConnectionClosed("500", "test")
             connection._on_open(mock.MagicMock())
             self.assertEqual(
                 m.output,