fix telethon bug when running in celery workers that close the event loop

src/auto_archiver/modules/telethon_extractor/telethon_extractor.py

@@ -1,3 +1,4 @@
+import asyncio
 import os
 import shutil
 import re
@@ -53,6 +54,16 @@ class TelethonExtractor(Extractor):
         logger.debug(f"Making a copy of the session file {base_session_filepath} to {self.session_file}.session")
         shutil.copy(base_session_filepath, f"{self.session_file}.session")
 
+        # ensure a running event loop exists (Needed when used by Celery workers which may close the default one)
+        try:
+            loop = asyncio.get_event_loop()
+            if loop.is_closed():
+                loop = asyncio.new_event_loop()
+                asyncio.set_event_loop(loop)
+        except RuntimeError:
+            loop = asyncio.new_event_loop()
+            asyncio.set_event_loop(loop)
+
         # initiate the client
         self.client = TelegramClient(self.session_file, self.api_id, self.api_hash)
 

tests/extractors/test_telethon_extractor.py

@@ -1,3 +1,4 @@
+import asyncio
 import os
 from datetime import date
 
@@ -60,3 +61,53 @@ def test_valid_url_regex(url, expected, get_lazy_module):
 def test_invite_pattern_regex(invite, expected, get_lazy_module):
     match = TelethonExtractor.invite_pattern.search(invite)
     assert bool(match) == expected
+
+
+def test_setup_with_closed_event_loop(get_lazy_module, tmp_path, mocker):
+    """
+    Simulate the Celery worker scenario where the asyncio event loop is closed
+    before setup() runs. The fix should create a new event loop so that
+    TelegramClient.start() does not raise 'Event loop is closed'.
+    """
+    # create a session file so setup doesn't fail on missing file
+    session_file = tmp_path / "test.session"
+    session_file.touch()
+
+    # close the current event loop to simulate a Celery worker environment
+    loop = asyncio.new_event_loop()
+    asyncio.set_event_loop(loop)
+    loop.close()
+
+    lazy_module = get_lazy_module("telethon_extractor")
+    module = lazy_module.load(
+        {"telethon_extractor": {"session_file": str(session_file), "api_id": 123, "api_hash": "ABC"}}
+    )
+
+    # setup should have succeeded and a new open event loop should exist
+    new_loop = asyncio.get_event_loop()
+    assert not new_loop.is_closed()
+    assert module.client is not None
+
+
+def test_setup_with_no_event_loop(get_lazy_module, tmp_path, mocker):
+    """
+    Simulate the scenario where there is no current event loop at all
+    (e.g. running in a non-main thread). The fix should create one.
+    """
+    session_file = tmp_path / "test.session"
+    session_file.touch()
+
+    # Remove the current event loop entirely
+    # In Python 3.12+, get_event_loop() in a non-main thread raises RuntimeError
+    mocker.patch("asyncio.get_event_loop", side_effect=RuntimeError("no current event loop"))
+    new_loop_mock = mocker.MagicMock()
+    new_loop_mock.is_closed.return_value = False
+    mocker.patch("asyncio.new_event_loop", return_value=new_loop_mock)
+    set_loop = mocker.patch("asyncio.set_event_loop")
+
+    lazy_module = get_lazy_module("telethon_extractor")
+    lazy_module.load({"telethon_extractor": {"session_file": str(session_file), "api_id": 123, "api_hash": "ABC"}})
+
+    # a new event loop should have been created and set
+    asyncio.new_event_loop.assert_called_once()
+    set_loop.assert_called_once_with(new_loop_mock)