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OpenStack Study: post_mortem_debug.py**** CubicPower OpenStack Study ****
# vim: tabstop=4 shiftwidth=4 softtabstop=4 # Copyright 2013 Red Hat, Inc. # All Rights Reserved. # # Licensed under the Apache License, Version 2.0 (the "License"); you may # not use this file except in compliance with the License. You may obtain # a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the # License for the specific language governing permissions and limitations # under the License. import pdb import traceback
**** CubicPower OpenStack Study **** def exception_handler(exc_info): """Exception handler enabling post-mortem debugging. A class extending testtools.TestCase can add this handler in setUp(): self.addOnException(post_mortem_debug.exception_handler) When an exception occurs, the user will be dropped into a pdb session in the execution environment of the failure. Frames associated with the testing framework are excluded so that the post-mortem session for an assertion failure will start at the assertion call (e.g. self.assertTrue) rather than the framework code that raises the failure exception (e.g. the assertTrue method). """ tb = exc_info[2] ignored_traceback = get_ignored_traceback(tb) if ignored_traceback: tb = FilteredTraceback(tb, ignored_traceback) traceback.print_exception(exc_info[0], exc_info[1], tb) pdb.post_mortem(tb)
**** CubicPower OpenStack Study **** def get_ignored_traceback(tb): """Retrieve the first traceback of an ignored trailing chain. Given an initial traceback, find the first traceback of a trailing chain of tracebacks that should be ignored. The criteria for whether a traceback should be ignored is whether its frame's globals include the __unittest marker variable. This criteria is culled from: unittest.TestResult._is_relevant_tb_level For example: tb.tb_next => tb0.tb_next => tb1.tb_next - If no tracebacks were to be ignored, None would be returned. - If only tb1 was to be ignored, tb1 would be returned. - If tb0 and tb1 were to be ignored, tb0 would be returned. - If either of only tb or only tb0 was to be ignored, None would be returned because neither tb or tb0 would be part of a trailing chain of ignored tracebacks. """ # Turn the traceback chain into a list tb_list = [] while tb: tb_list.append(tb) tb = tb.tb_next # Find all members of an ignored trailing chain ignored_tracebacks = [] for tb in reversed(tb_list): if '__unittest' in tb.tb_frame.f_globals: ignored_tracebacks.append(tb) else: break # Return the first member of the ignored trailing chain if ignored_tracebacks: return ignored_tracebacks[-1]
**** CubicPower OpenStack Study **** class FilteredTraceback(object): """Wraps a traceback to filter unwanted frames."""
**** CubicPower OpenStack Study **** def __init__(self, tb, filtered_traceback): """Constructor. :param tb: The start of the traceback chain to filter. :param filtered_traceback: The first traceback of a trailing chain that is to be filtered. """ self._tb = tb self.tb_lasti = self._tb.tb_lasti self.tb_lineno = self._tb.tb_lineno self.tb_frame = self._tb.tb_frame self._filtered_traceback = filtered_traceback @property
**** CubicPower OpenStack Study **** def tb_next(self): tb_next = self._tb.tb_next if tb_next and tb_next != self._filtered_traceback: return FilteredTraceback(tb_next, self._filtered_traceback)
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