me, 2.0: bugspot in python

me, 2.0: jose nazario beauty and the street

bugspot in python

i saw this discussion on hackernews, which links to a google blog post about how they try and predict bug hotspots based on past activity. pretty simple approach, not all that ineffective, either.

someone on HN had a working ruby tool for git in a few hours, but those are tools i don't use (git or ruby). so i wrote a version for subversion in python, which is below. my output is based on theirs since it made a lot of sense. one thing i think i may do is add support for arbitrary strings for the match conditions (e.g. whatever terms you team uses) and also a max "age" or timeline to start at.

#!/usr/bin/env python

"""
bugspot-svn.py 
copyright (c) 2011 jose nazario , all rights reserved
license: 2 clause BSD
"""

# see
# http://google-engtools.blogspot.com/2011/12/bug-prediction-at-google.html

def svnlog_parser(input):
    assert type(input) is file
    data = []
    while True:
        line = input.readline()
        if line.startswith('-'*30):
            if data:
                yield ''.join(data)
                data = []
        if line == '': raise StopIteration
        else:
            data.append(line)

if __name__ == '__main__':
    import math
    import os
    import re
    import sys
    import time

    try: 
        print 'Scanning %s' % sys.argv[1]
    except IndexError:
        print >> sys.stderr, 'Usage: %s /path/to/repo' % sys.argv[0]
        sys.exit(1)
                           
    s = svnlog_parser(os.popen('cd %s && svn log -v' % sys.argv[1]))
    message_matchers = [ re.compile(x, re.I) for x in ('fixes', 'fixed', 'closes', 'bug\w?#\d+', ) ]

    hotspots = {}
    messages = []
    times = []
    for m in s: 
        paths = []
        lines = m.split('\n')
        i = 0
        for line in lines:
            if line.startswith('-'*20):
                # seperator
                i += 1
                continue
            if i == 1:
                # revision | who | timestamp | N lines
                i += 1
                timestamp = ' '.join(line.split(' | ')[2].split()[:2])
                timestamp = int(time.strftime('%s', time.strptime(timestamp, '%Y-%m-%d %H:%M:%S')))
                times.append(timestamp)
                continue
            if line == 'Changed paths:': 
                # blah
                i += 1
                continue
            try:
                # actual files changed
                if line[3] in ('D', 'M', 'A'):
                    i += 1
                    paths.append(line.split(' ', 1)[1])
                    continue
            except IndexError: pass
            # and everything else is the changelog
            msg = ' '.join(lines[i:])
        for matcher in message_matchers:
            if matcher.findall(msg):
                messages.append(msg)
                for path in paths:
                    path = path.strip()
                    l = hotspots.get(path, [])
                    l.append(timestamp)
                    hotspots[path] = l
                break
    start = min(times)
    end = max(times)

    def score(ts):
        s = 0
        for t in ts:
            t = (float(t)-start)/(end-start)
            s += 1/(1+(math.e**(-12*t+12)))
        return s

    hotspots = [ (score(y),x) for x,y in hotspots.iteritems() ]
    hotspots.sort()
    hotspots.reverse()
    hotspots = [ (y,x) for x,y in hotspots ]
    hotspots = filter(lambda x: x[1] > 0.001, hotspots)
    print 'Found %d bugfix commits, with %d hotspots' % (len(messages), len(hotspots))
    print
    print 'Fixes:'
    for msg in messages:
        print '    - %s' % msg
    print
    print 'Hotspots:'
    for path, n in hotspots:
        print '    %.3f - %s' % (n, path)

output on the phoneyc trunk look like this:

Scanning /Users/jose/code/phoneyc/trunk
Found 6 bugfix commits, with 2 hotspots

Fixes:
    -  fix quoting issues 
    -  fix arg length 
    -  [phoneyc] support for  RTSP MPEG4 SP Control ActiveX Control "MP4Prefix" Property Buffer Overflow vuln module, exploit demo  
    -  [phoneyc] found an exploit for QvodCtrl at SecFocus, add.  fix: - add CLSID for QvodCtrl  - look for URL and url  - XXX case independent handling of methods etc? - proper length check - object instantiation can be done with name, not just id  
    -  [phoneyc] - handle the  redirect stuff as an href - fix up URLs that lack a needed trailing '/'  
    -  import order fixup fix sgmllib exception namespace  

Hotspots:
    0.463 - /phoneyc/trunk/honeyclient.py
    0.099 - /phoneyc/trunk/modules/jscript/NCTAudioFile2.js

i'll be testing it on larger codebases soon, i developed it against the svn repo of phoneyc.

if you use it, please let me know how you find it. i'll happily accept patches, too.

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Last modified: Saturday, Dec 17, 2011 @ 08:42am

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