Created
September 13, 2013 20:43
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Adds context to your stack traces
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import contextlib | |
import linecache | |
import logging | |
import sys | |
import traceback | |
try: | |
import cStringIO as StringIO | |
except ImportError: | |
import StringIO | |
class PurgingDictionary(dict): | |
"""Special dictionary that can be purged. | |
Calling purge() removes the keys that have not been requested since the | |
last call to purge(). | |
This is useful to remove keys that are not needed anymore, when the keys | |
cannot be weakly referenced. | |
""" | |
def __init__(self): | |
dict.__init__(self) | |
self.__seen_keys = set() | |
def __mark_seen(self, key): | |
while key is not None: | |
if key in self.__seen_keys: | |
break | |
self.__seen_keys.add(key) | |
key = key.f_back | |
def __getitem__(self, key): | |
self.__mark_seen(key) | |
return dict.__getitem__(self, key) | |
def get(self, key, default=None): | |
self.__mark_seen(key) | |
return dict.get(self, key, default) | |
def setdefault(self, key, default=None): | |
self.__mark_seen(key) | |
return dict.setdefault(self, key, default) | |
def purge(self): | |
"""Removes entries that have not been queried since the last call. | |
""" | |
if not self.__seen_keys: | |
self.clear() | |
self.__seen_keys = set() | |
return | |
for k in self.keys(): | |
if k not in self.__seen_keys: | |
del self[k] | |
self.__seen_keys = set() | |
# Gets the current frame (from logging) | |
def currentframe(): | |
try: | |
raise Exception | |
except: | |
return sys.exc_info()[2].tb_frame.f_back | |
if hasattr(sys, '_getframe'): currentframe = lambda: sys._getframe(3) | |
class DefaultContext(object): | |
"""Default context formatter. | |
""" | |
def __init__(self, msg=None, **kwargs): | |
self.msg = msg | |
self.kwargs = kwargs | |
def __str__(self): | |
if self.kwargs: | |
kw = ', '.join('%s=%r' % (k, v) | |
for k, v in self.kwargs.iteritems()) | |
if self.msg: | |
return "%s (%s)" % (self.msg, kw) | |
else: | |
return "(%s)" % kw | |
elif self.msg: | |
return self.msg | |
_context_class = DefaultContext | |
def set_context_class(cls): | |
"""Changes the class used to build/format contexts. | |
This class gets passed the arguments that were given to push() or pushed(), | |
and is converted to a string to be put in the traceback. | |
""" | |
global _context_class | |
_context_class = cls | |
pushed_infos = PurgingDictionary() | |
class Formatter(logging.Formatter): | |
"""Logging formatter that inserts the context objects in the traceback. | |
""" | |
def formatException(self, ei): | |
etype, value, tb = ei[:3] | |
formatted = [] | |
formatted.append("Traceback (most recent call last):") | |
while tb is not None: | |
f = tb.tb_frame | |
lineno = tb.tb_lineno | |
co = f.f_code | |
filename = co.co_filename | |
name = co.co_name | |
item = ' File "%s", line %d, in %s' % (filename, lineno, name) | |
frame_contexts = pushed_infos.get(f) | |
if frame_contexts: | |
for ctx in frame_contexts: | |
item += '\n %s' % ctx | |
linecache.checkcache(filename) | |
line = linecache.getline(filename, lineno, f.f_globals) | |
if line: | |
item += '\n ' + line.strip() | |
formatted.append(item) | |
tb = tb.tb_next | |
formatted.append("%s: %s" % (etype.__name__, value.message)) | |
return '\n'.join(formatted) | |
def push(*args, **kwargs): | |
"""Push some context onto the stack. | |
You don't have to pop this, it is associated with the caller's stack frame. | |
""" | |
f = currentframe().f_back | |
frame_contexts = pushed_infos.setdefault(f, []) | |
frame_contexts.append(_context_class(*args, **kwargs)) | |
@contextlib.contextmanager | |
def pushed(*args, **kwargs): | |
"""Push some context onto the stack. | |
The context is removed when leaving the context manager. | |
""" | |
frame_contexts = pushed_infos.setdefault(currentframe().f_back, []) | |
ctx = _context_class(*args, **kwargs) | |
idx = len(frame_contexts) | |
frame_contexts.append(ctx) | |
try: | |
yield | |
finally: | |
del frame_contexts[idx] |
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Moved to its own Github repository!
remram44:logstack
Perhaps this could be made a part of something like structlog.