Python decarator that sends backtraces via POST to a remote server

backtracer.py

#!/usr/bin/env python -u
# vim:ts=4:sts=4:sw=4:et:wrap:ai:fileencoding=utf-8:


"""Decorator to log a function's backtrace to a remote server.

Based on client/backtrace.py
from http://github.com/tmacam/DistributedCrawler.
"""


from functools import wraps
import json
import StringIO
import sys
import traceback
import urllib
import urllib2


__all__ = ('backtrace_logged', 'exceptions_stripped')
__version__ = "0.4.engine"
__date__ = '2012-11-05 13:19:24 -0200 (Mon, 05 Nov 2012)'
__author__ = "Tiago Alves Macambira"
__copyright__ = 'Copyright (c) 2012 Tiago Alves Macambira'
__license__ = 'X11'
__url__ = 'git://gist.github.com/4017891.git'


def exceptions_stripped(fn):
    """Strips and consumes any exception fn may raise."""
    @wraps(fn)
    def wrapper_fn(*args, **kwds):
        try:
            return fn(*args, **kwds)
        except:
            pass
    return wrapper_fn


@exceptions_stripped
def __post_backtrace(url, backtrace_str, extras=None):
    form_data = {'backtrace': backtrace_str}
    if extras:
        form_data.update(extras)
    try:
        headers = {'Content-Type': 'application/json'}
        data = json.dumps(form_data)
    except:
        # Let's hope form-encoding is more permisive...
        headers = None
        data = urllib.urlencode(form_data)
    req = urllib2.Request(url, data, headers)
    res = urllib2.urlopen(req)
    res.read()
    res.close()


@exceptions_stripped
def __collect_and_log_backtrace(log_to_stderr, log_to_url, extras=None):
    # Get backtrace information from stack
    backtrace_fn = StringIO.StringIO()
    traceback.print_exc(file=backtrace_fn)
    backtrace_str = backtrace_fn.getvalue()
    # Print and forward the backtrace as requested
    if log_to_stderr:
        sys.stderr.write("ERROR! BACKTRACE FOLLOWS:\n")
        sys.stderr.write(backtrace_str)
        sys.stderr.write("\n")
    if log_to_url:
        __post_backtrace(log_to_url, backtrace_str, extras)


def backtrace_logged(log_to_stderr=True, log_to_url=None, extras=None):
    """Decorator to log a function's backtrace to a remote server.

    Args:
        log_to_stderr: Whether we should print the backtrace to the stderr.
                       Defaults to true.
        log_to_url: If not None, we will do a POST request of the backtrace
                    to the provided URL.
        extras: dict with extra string values to be sent along backtrace
                data in a POST request to `log_to_url`.
    """
    def backtrace_wraper(fn):
        @wraps(fn)
        def new_func(*args, **kwds):
            try:
                return fn(*args, **kwds)
            except:
                __collect_and_log_backtrace(log_to_stderr, log_to_url, extras)
                # Bubble up the exception
                raise
        return new_func
    return backtrace_wraper


def main():
    @backtrace_logged(log_to_stderr=True,
                      log_to_url="http://localhost:8700/backtrace")
    def just_fail():
        raise TypeError("Duh!!!")

    just_fail()

    print "Done"


if __name__ == '__main__':
    main()