What the heck went wrong?
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What the heck went wrong? Presentation Transcript

  • 1. What the heck went wrong? Andy McKay andym on #django clearwind consulting andy@clearwind.ca @clearwind
  • 2. debugging django
  • 3. reporting errors
  • 4. not a question of if...
  • 5. development → production
  • 6. development use the dev. server python manage.py runserver
  • 7. development turn on debug DEBUG = True
  • 8. development assert False
  • 9. development a print print "some debugging statement"
  • 10. development a print print "some debugging statement" print some_variable print type(some_variable)
  • 11. there's a problem
  • 12. development mod_wsgi IOError: sys.stdout access restricted by mod_wsgi WSGIRestrictStdout Off http://code.google.com/p/modwsgi/wiki/ApplicationIssues
  • 13. logging http://www.flickr.com/photos/astro-dudes/1492818224/
  • 14. development http://docs.python.org/library/logging.html import logging logging.basicConfig( level = logging.DEBUG, format = '%(asctime)s %(levelname)s %(message)s', )
  • 15. development import logging log.debug("My brilliant debug message")
  • 16. import logging development import logging.handlers if getattr(settings, "LOG_FILENAME", None): logger = logging.getLogger("django") handler = logging.handlers.RotatingFileHandler(settings.LOG_FILENAME) formatter = logging.Formatter("%(asctime)s - %(levelname)s - %(message)s") handler.setFormatter(formatter) logger.addHandler(handler) else: # so that if you don't have LOG_FILENAME defined, don't blow up class NullHandler(logging.Handler): def emit(self, record): pass logging.getLogger("django").addHandler(NullHandler())
  • 17. development pdb http://docs.python.org/library/pdb.html
  • 18. development import pdb; pdb.set_trace() Django version 1.2 pre-alpha, using settings 'test_profiler.settings' Development server is running at http://0.0.0.0:8000/ Quit the server with CONTROL-C. > /mnt/hgfs/sandboxes/test_profiler/profiler/middleware.py(12) process_response() -> url = request.get_full_path() (Pdb)
  • 19. development l: shows lines of code at your current point n: execute the next line s: step into c: continue q: quit locals(): see what's in your current scope
  • 20. development pdb is essential
  • 21. there's a problem
  • 22. development leave pdb in and your site...
  • 23. development werkzeug debugger easy_install Werkzeug http://dev.pocoo.org/projects/werkzeug/wiki/UsingDebuggerWithDjango
  • 24. development #!/usr/bin/env python from werkzeug import run_simple, DebuggedApplication from django.core.handlers.wsgi import WSGIHandler # This is only needed for Django versions < [7537]: def null_technical_500_response(request, exc_type, exc_value, tb): raise exc_type, exc_value, tb from django.views import debug debug.technical_500_response = null_technical_500_response if __name__ == '__main__': run_simple('localhost', 8080, DebuggedApplication(WSGIHandler(), True))
  • 25. development
  • 26. development unit tests
  • 27. development django-debug-toolbar http://github.com/robhudson/django-debug-toolbar/tree/master
  • 28. development rocks!
  • 29. development MIDDLEWARE_CLASSES = ( [...snip] 'debug_toolbar.middleware.DebugToolbarMiddleware', ) INSTALLED_APPS = ( [...snip] 'debug_toolbar' ) INTERNAL_IPS = ('127.0.0.1',)
  • 30. development
  • 31. development cheaper and easier
  • 32. staging continuous integration e.g: Teamcity, Integrity, buildbot, Tinderbox ... others are available
  • 33. staging custom test runner TeamCity: http://bit.ly/geAA [..snip] if hasTeamcity and underTeamcity(): result = TeamcityTestRunner().run(suite) else: result = unittest.TextTestRunner(verbosity=verbosity).run(suite)
  • 34. staging
  • 35. production varies upon server mod_wsgi → http://code.google.com/p/modwsgi/wiki/DebuggingTechniques mod_python → http://yenaer.com/blog/2008/jan/12/debugging-modpython-scripts-apache-and-pdb
  • 36. production errors http://docs.djangoproject.com/en/dev/howto/error-reporting/
  • 37. production 404 and 500 (has to be in root url.conf) handler404 = 'mysite.views.custom_404' handler500 = 'mysite.views.custom_500' http://docs.djangoproject.com/en/dev/topics/http/views/
  • 38. production emailed DEBUG = False ADMIN = ( ('Andy', 'andy@clearwind.ca'), )
  • 39. production Traceback (most recent call last):  File "/usr/lib/python2.5/site-packages/django/core/handlers/base.py", line 86, in get_response    response = callback(request, *callback_args, **callback_kwargs)  File "/usr/lib/python2.5/site-packages/django/contrib/admin/sites.py", line 154, in root    return shortcut(request, *url.split('/')[1:])  File "/usr/lib/python2.5/site-packages/django/contrib/contenttypes/views.py", line 57, in shortcut    object_domain = Site.objects.get_current().domain  File "/usr/lib/python2.5/site-packages/django/contrib/sites/models.py", line 22, in get_current    current_site = self.get(pk=sid)  File "/usr/lib/python2.5/site-packages/django/db/models/manager.py", line 93, in get    return self.get_query_set().get(*args, **kwargs)  File "/usr/lib/python2.5/site-packages/django/db/models/query.py", line 298, in get    num = len(clone)  File "/usr/lib/python2.5/site-packages/django/db/models/query.py", line 154, in __len__    self._result_cache = list(self.iterator())  File "/usr/lib/python2.5/site-packages/django/db/models/query.py", line 269, in iterator    for row in self.query.results_iter():  File "/usr/lib/python2.5/site-packages/django/db/models/sql/query.py", line 206, in results_iter    for rows in self.execute_sql(MULTI):  File "/usr/lib/python2.5/site-packages/django/db/models/sql/query.py", line 1723, in execute_sql    cursor.execute(sql, params) ProgrammingError: relation "django_site" does not exist <WSGIRequest GET:<QueryDict: {}>, POST:<QueryDict: {}>, COOKIES:{'__utma': '90285002.4337325975145378300.1232037035.1233126418.1233185854.12', '__utmb': '90285002.2.10.1233185854', '__utmc': '90285002', '__utmz': '90285002.1232037035.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)', 'sessionid': 'b139e8d00ed433fb5e6dff50a3956036'}, META:{'DOCUMENT_ROOT': '/htdocs', 'GATEWAY_INTERFACE': 'CGI/1.1', 'HTTP_ACCEPT': 'text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5', 'HTTP_ACCEPT_ENCODING': 'gzip, deflate', 'HTTP_ACCEPT_LANGUAGE': 'en-us', 'HTTP_CONNECTION': 'keep-alive', 'HTTP_COOKIE': '__utmz=90285002.1232037035.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); __utma=90285002.4337325975145378300.1232037035.1233126418.1233185854.12; __utmc=90285002; __utmb=90285002.2.10.1233185854; sessionid=b139e8d00ed433fb5e6dff50a3956036', 'HTTP_HOST': 'www.areciboapp.com', 'HTTP_REFERER': 'http://www.areciboapp.com/arecibo-admin/singleblog/post/7/', 'HTTP_USER_AGENT': 'Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_6; en-us) AppleWebKit/525.27.1 (KHTML, like Gecko) Version/3.2.1 Safari/525.27.1', 'PATH': '/usr/local/bin:/usr/bin:/bin', 'PATH_INFO': u'/arecibo-admin/r/18/7/', 'PATH_TRANSLATED': '/var/www/arecibo/django.wsgi/arecibo-admin/r/18/7/', 'QUERY_STRING': '', 'REMOTE_ADDR': '70.79.161.59', 'REMOTE_PORT': '63593', 'REQUEST_METHOD': 'GET', 'REQUEST_URI': '/arecibo-admin/r/18/7/', 'SCRIPT_FILENAME': '/var/www/arecibo/django.wsgi', 'SCRIPT_NAME': u'', 'SERVER_ADDR': '216.139.224.26', 'SERVER_ADMIN': '[no address given]', 'SERVER_NAME': 'www.areciboapp.com', 'SERVER_PORT': '80', 'SERVER_PROTOCOL': 'HTTP/1.1', 'SERVER_SIGNATURE': '<address>Apache/2.2.8 (Ubuntu) DAV/2 SVN/1.4.6 mod_python/3.3.1 Python/2.5.2 mod_ssl/2.2.8 OpenSSL/0.9.8g mod_wsgi/1.3 Server at www.areciboapp.com Port 80</address>n', 'SERVER_SOFTWARE': 'Apache/2.2.8 (Ubuntu) DAV/2 SVN/1.4.6 mod_python/3.3.1 Python/2.5.2 mod_ssl/2.2.8 OpenSSL/0.9.8g mod_wsgi/1.3', 'mod_wsgi.application_group': 'areciboapp.com|', 'mod_wsgi.callable_object': 'application', 'mod_wsgi.case_sensitivity': '1', 'mod_wsgi.listener_host': '', 'mod_wsgi.listener_port': '80', 'mod_wsgi.output_buffering': '0', 'mod_wsgi.process_group': 'www-data', 'mod_wsgi.reload_mechanism': '0', 'mod_wsgi.script_reloading': '1', 'wsgi.errors': <mod_wsgi.Log object at 0x8c0d620>, 'wsgi.input': <mod_wsgi.Input object at 0xb469958>, 'wsgi.multiprocess': True, 'wsgi.multithread': False, 'wsgi.run_once': False, 'wsgi.url_scheme': 'http', 'wsgi.version': (1, 0)}>
  • 40. production arecibo http://www.areciboapp.com/ http://www.areciboapp.com/listener/docs/django/
  • 41. production get account Install Arecibo library ARECIBO_PUBLIC_ACCOUNT_NUMBER = "xxxx"
  • 42. production add to error from arecibo.wrapper import post def application_error(request): t = loader.get_template('500.html') uid = post(request, 500) c = RequestContext(request, {"uid": uid}) return HttpResponse(t.render(c), status=500)
  • 43. production
  • 44. honourable mentions django-db-log http://code.google.com/p/django-db-log/ "Logs Django exceptions to your database handler."
  • 45. honourable mentions django-sql-profiler http://code.google.com/p/django-sql-profiler "Records every SQL query in Django in the database so that you can find slow queries in your site."
  • 46. The error message is the Truth. The error message is God. James Bennett, earlier today. Andy McKay clearwind consulting andy@clearwind.ca @clearwind slides will be going on http://djangozen.com