timeout: Rename to unsafe_timeout.

This timeout strategy using asynchronous exceptions has a number of
safety caveats (read the docstring!!) and should only be used in very
specific circumstances.

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

zerver/lib/markdown/__init__.py

@@ -68,7 +68,7 @@ from zerver.lib.outgoing_http import OutgoingSession
 from zerver.lib.subdomains import is_static_or_current_realm_url
 from zerver.lib.tex import render_tex
 from zerver.lib.thumbnail import user_uploads_or_external
-from zerver.lib.timeout import timeout
+from zerver.lib.timeout import unsafe_timeout
 from zerver.lib.timezone import common_timezones
 from zerver.lib.types import LinkifierDict
 from zerver.lib.url_encoding import encode_stream, hash_util_encode
@@ -2667,7 +2667,7 @@ def do_convert(
         # extremely inefficient in corner cases) as well as user
         # errors (e.g. a linkifier that makes some syntax
         # infinite-loop).
-        rendering_result.rendered_content = timeout(5, lambda: _md_engine.convert(content))
+        rendering_result.rendered_content = unsafe_timeout(5, lambda: _md_engine.convert(content))
 
         # Throw an exception if the content is huge; this protects the
         # rest of the codebase from any bugs where we end up rendering

zerver/lib/test_classes.py

@@ -1560,7 +1560,7 @@ Output:
         markdown.__init__.do_convert.
         """
         with mock.patch(
-            "zerver.lib.markdown.timeout", side_effect=subprocess.CalledProcessError(1, [])
+            "zerver.lib.markdown.unsafe_timeout", side_effect=subprocess.CalledProcessError(1, [])
         ), self.assertLogs(level="ERROR"):  # For markdown_logger.exception
             yield
 

zerver/lib/timeout.py

@@ -22,7 +22,7 @@ class TimeoutExpiredError(Exception):
 ResultT = TypeVar("ResultT")
 
 
-def timeout(timeout: float, func: Callable[[], ResultT]) -> ResultT:
+def unsafe_timeout(timeout: float, func: Callable[[], ResultT]) -> ResultT:
     """Call the function in a separate thread.
     Return its return value, or raise an exception,
     within approximately 'timeout' seconds.

zerver/tests/test_markdown.py

@@ -3305,7 +3305,7 @@ class MarkdownErrorTests(ZulipTestCase):
         throws an exception"""
         msg = "mock rendered message\n" * 10 * settings.MAX_MESSAGE_LENGTH
 
-        with mock.patch("zerver.lib.markdown.timeout", return_value=msg), mock.patch(
+        with mock.patch("zerver.lib.markdown.unsafe_timeout", return_value=msg), mock.patch(
             "zerver.lib.markdown.markdown_logger"
         ):
             with self.assertRaises(MarkdownRenderingError):

zerver/tests/test_timeout.py

@@ -4,7 +4,7 @@ import traceback
 from unittest import skipIf
 
 from zerver.lib.test_classes import ZulipTestCase
-from zerver.lib.timeout import TimeoutExpiredError, timeout
+from zerver.lib.timeout import TimeoutExpiredError, unsafe_timeout
 
 
 class TimeoutTestCase(ZulipTestCase):
@@ -20,12 +20,12 @@ class TimeoutTestCase(ZulipTestCase):
         return 42  # nocoverage
 
     def test_timeout_returns(self) -> None:
-        ret = timeout(1, lambda: 42)
+        ret = unsafe_timeout(1, lambda: 42)
         self.assertEqual(ret, 42)
 
     def test_timeout_exceeded(self) -> None:
         try:
-            timeout(1, lambda: self.sleep_x_seconds_y_times(0.1, 50))
+            unsafe_timeout(1, lambda: self.sleep_x_seconds_y_times(0.1, 50))
             raise AssertionError("Failed to raise a timeout")
         except TimeoutExpiredError as exc:
             tb = traceback.format_tb(exc.__traceback__)
@@ -34,7 +34,7 @@ class TimeoutTestCase(ZulipTestCase):
 
     def test_timeout_raises(self) -> None:
         try:
-            timeout(1, self.something_exceptional)
+            unsafe_timeout(1, self.something_exceptional)
             raise AssertionError("Failed to raise an exception")
         except ValueError as exc:
             tb = traceback.format_tb(exc.__traceback__)
@@ -47,7 +47,7 @@ class TimeoutTestCase(ZulipTestCase):
         # kill it
         with self.assertLogs(level="WARNING") as m:
             try:
-                timeout(1, lambda: self.sleep_x_seconds_y_times(5, 1))
+                unsafe_timeout(1, lambda: self.sleep_x_seconds_y_times(5, 1))
                 raise AssertionError("Failed to raise a timeout")
             except TimeoutExpiredError as exc:
                 tb = traceback.format_tb(exc.__traceback__)