outgoing_webhook: Set a default timeout of 10s.

Support for the timeouts, and tests for them, was added in
53a8b2ac87 -- though no code could have set them after 31597cf33e.

Add a 10-second default timeout.  Observationally, p99 is just about
5s, with everything else being previously being destined to meet the
30s worker timeout; 10s provides a sizable buffer between them.

Fixes #17742.

zerver/lib/outgoing_webhook.py

@@ -5,8 +5,10 @@ from time import perf_counter
 from typing import Any, AnyStr, Dict, Optional
 
 import requests
+from django.conf import settings
 from django.utils.translation import gettext as _
 from requests import Response, Session
+from urllib3 import HTTPResponse
 
 from version import ZULIP_VERSION
 from zerver.decorator import JsonableError
@@ -26,12 +28,26 @@ from zerver.models import (
 )
 
 
+class TimeoutAdapter(requests.adapters.HTTPAdapter):
+    def __init__(self, timeout: Optional[int] = None, *args: Any, **kwargs: Any) -> None:
+        self.timeout = timeout
+        super().__init__(*args, *kwargs)
+
+    def send(self, *args: Any, **kwargs: Any) -> HTTPResponse:
+        if kwargs.get("timeout") is None:
+            kwargs["timeout"] = self.timeout
+        return super().send(*args, **kwargs)
+
+
 class OutgoingWebhookServiceInterface(metaclass=abc.ABCMeta):
     def __init__(self, token: str, user_profile: UserProfile, service_name: str) -> None:
         self.token: str = token
         self.user_profile: UserProfile = user_profile
         self.service_name: str = service_name
         self.session: Session = Session()
+        timeout_adapter = TimeoutAdapter(timeout=settings.OUTGOING_WEBHOOK_TIMEOUT_SECONDS)
+        self.session.mount("http://", timeout_adapter)
+        self.session.mount("https://", timeout_adapter)
         self.session.headers.update(
             {
                 "X-Smokescreen-Role": "webhook",
@@ -363,7 +379,9 @@ def do_rest_call(
             event["command"],
             event["service_name"],
         )
-        failure_message = "A timeout occurred."
+        failure_message = (
+            f"Request timed out after {settings.OUTGOING_WEBHOOK_TIMEOUT_SECONDS} seconds."
+        )
         request_retry(event, failure_message=failure_message)
         return None