[gentoo-portage-dev] [PATCH] AsyncioEventLoop: exit after unhandled exception (bug 658684)

[Zac Medico]

Fix portage commands to exit immediately for any unhandled
exceptions that are raised while the asyncio event loop is running
without a tty. If we have a tty then start the debugger,
since in might aid in diagnosis of the problem.

In order to avoid potential interference with API consumers, do not
call set_exception_handler unless portage._internal_caller is True.

Bug: https://bugs.gentoo.org/658684
---
 pym/portage/util/_eventloop/asyncio_event_loop.py | 31 +++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/pym/portage/util/_eventloop/asyncio_event_loop.py b/pym/portage/util/_eventloop/asyncio_event_loop.py
index c07b71103c..ea0e03b23b 100644
--- a/pym/portage/util/_eventloop/asyncio_event_loop.py
+++ b/pym/portage/util/_eventloop/asyncio_event_loop.py
@@ -2,7 +2,9 @@
 # Distributed under the terms of the GNU General Public License v2
 
 import os
+import pdb
 import signal
+import sys
 
 try:
 	import asyncio as _real_asyncio
@@ -53,6 +55,35 @@ class AsyncioEventLoop(_AbstractEventLoop):
 		self.get_debug = loop.get_debug
 		self._wakeup_fd = -1
 
+		if portage._internal_caller:
+			loop.set_exception_handler(self._internal_caller_exception_handler)
+
+	@staticmethod
+	def _internal_caller_exception_handler(loop, context):
+		"""
+		An exception handler which drops to a pdb shell if std* streams
+		refer to a tty, and otherwise kills the process with SIGTERM.
+
+		In order to avoid potential interference with API consumers, this
+		implementation is only used when portage._internal_caller is True.
+		"""
+		loop.default_exception_handler(context)
+		if 'exception' in context:
+			# If we have a tty then start the debugger, since in might
+			# aid in diagnosis of the problem. If there's no tty, then
+			# exit immediately.
+			if all(s.isatty() for s in (sys.stdout, sys.stderr, sys.stdin)):
+				pdb.set_trace()
+			else:
+				# Normally emerge will wait for all coroutines to complete
+				# after SIGTERM has been received. However, an unhandled
+				# exception will prevent the interrupted coroutine from
+				# completing, therefore use the default SIGTERM handler
+				# in order to ensure that emerge exits immediately (though
+				# uncleanly).
+				signal.signal(signal.SIGTERM, signal.SIG_DFL)
+				os.kill(os.getpid(), signal.SIGTERM)
+
 	def _create_future(self):
 		"""
 		Provide AbstractEventLoop.create_future() for python3.4.
-- 
2.13.6