streams: Remove inappropriate use of zerver.lib.timeout.

zerver.lib.timeout abuses asynchronous exceptions, so it’s only safe
to use on CPU computations with no side effects.

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

zerver/tests/test_message_topics.py

@@ -4,8 +4,6 @@ from django.utils.timezone import now as timezone_now
 
 from zerver.actions.streams import do_change_stream_permission
 from zerver.lib.test_classes import ZulipTestCase
-from zerver.lib.test_helpers import timeout_mock
-from zerver.lib.timeout import TimeoutExpiredError
 from zerver.models import Message, UserMessage
 from zerver.models.clients import get_client
 from zerver.models.realms import get_realm
@@ -291,7 +289,6 @@ class TopicDeleteTest(ZulipTestCase):
             acting_user=user_profile,
         )
         # Delete the topic should now remove all messages
-        with timeout_mock("zerver.views.streams"):
         result = self.client_post(
             endpoint,
             {
@@ -304,7 +301,6 @@ class TopicDeleteTest(ZulipTestCase):
         self.assertTrue(Message.objects.filter(id=initial_last_msg_id).exists())
 
         # Delete again, to test the edge case of deleting an empty topic.
-        with timeout_mock("zerver.views.streams"):
         result = self.client_post(
             endpoint,
             {
@@ -328,7 +324,7 @@ class TopicDeleteTest(ZulipTestCase):
 
         self.login_user(user_profile)
         endpoint = "/json/streams/" + str(stream.id) + "/delete_topic"
-        with mock.patch("zerver.views.streams.timeout", side_effect=TimeoutExpiredError):
+        with mock.patch("time.monotonic", side_effect=[10000, 10051]):
             result = self.client_post(
                 endpoint,
                 {

zerver/views/streams.py

@@ -1,5 +1,6 @@
+import time
 from collections import defaultdict
-from typing import Any, Callable, Dict, List, Literal, Mapping, Optional, Sequence, Set, Union
+from typing import Any, Callable, Dict, List, Mapping, Optional, Sequence, Set, Union
 
 import orjson
 from django.conf import settings
@@ -66,7 +67,6 @@ from zerver.lib.streams import (
     stream_to_dict,
 )
 from zerver.lib.subscription_info import gather_subscriptions
-from zerver.lib.timeout import TimeoutExpiredError, timeout
 from zerver.lib.topic import (
     get_topic_history_for_public_stream,
     get_topic_history_for_stream,
@@ -922,14 +922,16 @@ def delete_in_topic(
     # the user can see are returned in the query.
     messages = bulk_access_stream_messages_query(user_profile, messages, stream)
 
-    def delete_in_batches() -> Literal[True]:
     # Topics can be large enough that this request will inevitably time out.
     # In such a case, it's good for some progress to be accomplished, so that
     # full deletion can be achieved by repeating the request. For that purpose,
     # we delete messages in atomic batches, committing after each batch.
     # TODO: Ideally this should be moved to the deferred_work queue.
+    start_time = time.monotonic()
     batch_size = RETENTION_STREAM_MESSAGE_BATCH_SIZE
     while True:
+        if time.monotonic() >= start_time + 50:
+            return json_success(request, data={"complete": False})
         with transaction.atomic(durable=True):
             messages_to_delete = messages.order_by("-id")[0:batch_size].select_for_update(
                 of=("self",)
@@ -938,14 +940,6 @@ def delete_in_topic(
                 break
             do_delete_messages(user_profile.realm, messages_to_delete)
 
-        # timeout() in which we call this function requires non-None return value.
-        return True
-
-    try:
-        timeout(50, delete_in_batches)
-    except TimeoutExpiredError:
-        return json_success(request, data={"complete": False})
-
     return json_success(request, data={"complete": True})