Merge pull request #92 from minrk/faulthandler

patch faulthandler defaults to underlying stderr.

This redirects faulthandler to a real file descriptor instead of a zmq socket, so that in the event of a hard C-level crash, traceback data can still get logged.

Closes #91.

Author: fperez

ipykernel/kernelapp.py

@@ -303,7 +303,32 @@ def init_io(self):
         if self.displayhook_class:
             displayhook_factory = import_item(str(self.displayhook_class))
             sys.displayhook = displayhook_factory(self.session, self.iopub_socket)
+        
+        self.patch_io()
+    
+    def patch_io(self):
+        """Patch important libraries that can't handle sys.stdout forwarding"""
+        try:
+            import faulthandler
+        except ImportError:
+            pass
+        else:
+            faulthandler_enable = faulthandler.enable
+            faulthandler_register = faulthandler.register
+            # Warning: this is a monkeypatch of `faulthandler.enable`, watch for possible
+            # updates to the upstream API and update accordingly (up-to-date as of Python 3.5):
+            # https://docs.python.org/3/library/faulthandler.html#faulthandler.enable
+
+            # change default file to __stderr__ from forwarded stderr
+            def enable(file=sys.__stderr__, all_threads=True, **kwargs):
+                return faulthandler_enable(file=file, all_threads=all_threads, **kwargs)
 
+            def register(signum, file=sys.__stderr__, all_threads=True, chain=False, **kwargs):
+                return faulthandler_register(signum, file=file, all_threads=all_threads, chain=chain, **kwargs)
+
+            faulthandler.enable = enable
+            faulthandler.register = register
+    
     def init_signal(self):
         signal.signal(signal.SIGINT, signal.SIG_IGN)
 

ipykernel/tests/test_kernel.py

@@ -189,6 +189,20 @@ def test_save_history():
         nt.assert_in(u'a=1', content)
         nt.assert_in(u'b=u"abcþ"', content)
 
+
+@dec.skip_without('faulthandler')
+def test_smoke_faulthandler():
+    with kernel() as kc:
+        code = u'\n'.join([
+            'import faulthandler, signal',
+            'faulthandler.enable()',
+            'faulthandler.register(signal.SIGTERM)',
+        ])
+        _, reply = execute(code, kc=kc)
+        print(_)
+        nt.assert_equal(reply['status'], 'ok', reply.get('traceback', ''))
+
+
 def test_help_output():
     """ipython kernel --help-all works"""
     tt.help_all_output_test('kernel')