enkel/batteri/error_handler.py

   1 # This file is part of the Enkel web programming library.
   2 #
   3 # Copyright (C) 2007 Espen Angell Kristiansen (espeak@users.sourceforge.net)
   4 #
   5 # This program is free software; you can redistribute it and/or
   6 # modify it under the terms of the GNU General Public License
   7 # as published by the Free Software Foundation; either version 2
   8 # of the License, or (at your option) any later version.
   9 #
  10 # This program is distributed in the hope that it will be useful,
  11 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 # GNU General Public License for more details.
  14 #
  15 # You should have received a copy of the GNU General Public License
  16 # along with this program; if not, write to the Free Software
  17 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  18
  19 """ Error handling middleware. """
  20
  21 from BaseHTTPServer import BaseHTTPRequestHandler
  22 import logging
  23
  24 from enkel.error import EnkelUserError, EnkelFatal, EnkelWarning
  25 from enkel.error.http import HttpUserError
  26
  27
  28
  29 def handle_http_user_error(env, start_response):
  30         e = env["wsgiorg.routing_args"][0][0]
  31         status = "%d %s" % (e.NUMBER,
  32                         BaseHTTPRequestHandler.responses[e.NUMBER])
  33         start_response(status, [("content-type", "text/html")])
  34         yield "<html><body><h1>%(short_message)s</h1>"\
  35                         "%(long_message)s</body></html>" % e.__dict__
  36
  37 def handle_user_error(env, start_response):
  38         e = env["wsgiorg.routing_args"][0][0]
  39         status = "500 error"
  40         start_response(status, [("content-type", "text/html")])
  41         yield "<html><body><h1>%(short_message)s</h1>"\
  42                         "%(long_message)s</body></html>" % e.__dict__
  43
  44
  45 def handle_other_error(env, start_response):
  46         start_response("500 error", [("content-type", "text/plain")])
  47         return ["Internal server error"]
  48
  49
  50 class ErrorHandler(object):
  51         """ A WSGI middleware for handling errors.
  52         It traps errors and forwards them to another WSGI app.
  53         Before forwarding, the exception is added to the WSGI environ
  54         dict like this: environ["wsgiorg.routing_args"] = ([exception], {}).
  55
  56         Example error handler
  57         =====================
  58                 >>> from enkel.wsgiapp import WsgiApp
  59                 >>> class MyErrorHandler(WsgiApp)
  60                 ...     def run_app(self, exception):
  61                 ...             return str(exception)
  62         """
  63         def __init__(self, app, use_log=True,
  64                         http_error = handle_http_user_error,
  65                         user_error = handle_user_error,
  66                         other_error = handle_other_error):
  67                 """
  68                 @param use_log: If True, log errors using the logging module.
  69                                 HttpUserError and EnkelUserError are sent to
  70                                 logging.debug and other exceptions are sent to
  71                                 logging.error. exc_info=True is used in all 3 cases.
  72                 @param http_error: A wsgi app that handels any
  73                                 L{enkel.error.http.HttpUserError} that is raised.
  74                 @param user_error: A wsgi app that handels any
  75                                 L{enkel.error.EnkelUserError} that is raised.
  76                 @param other_error: A wsgi app that handels any error except
  77                                 HttpUserError and EnkelUserError.
  78                 """
  79                 self.app = app
  80                 self.use_log = use_log
  81                 self.handle_user_error = user_error
  82                 self.handle_http_error = http_error
  83                 self.handle_other_error = other_error
  84
  85         def __call__(self, env, start_response):
  86                 try:
  87                         return self.app(env, start_response)
  88                 except HttpUserError, e:
  89                         if self.use_log:
  90                                 logging.debug(str(e), exc_info=True)
  91                         env["wsgiorg.routing_args"] = ([e], {})
  92                         return self.handle_http_error(env, start_response)
  93                 except EnkelUserError, e:
  94                         if self.use_log:
  95                                 logging.debug(str(e), exc_info=True)
  96                         env["wsgiorg.routing_args"] = ([e], {})
  97                         return self.handle_user_error(env, start_response)
  98                 except Exception, e:
  99                         if self.use_log:
 100                                 logging.error(str(e), exc_info=True)
 101                         env["wsgiorg.routing_args"] = ([e], {})
 102                         return self.handle_other_error(env, start_response)