cgitb wierdness with CP

[Scott Chapman]

Every time I get a database error, I get a traceback from cgitb.
Here's my basic setup:

import cherrypy
import cgitb, sys

def cgitb_display_err():
"""Replace the default error response with an HTML traceback from
cgitb."""

tb = cgitb.html(sys.exc_info())
def set_tb():
cherrypy.response.body = tb
cherrypy.response.headers['Content-Length'] = None
cherrypy.request.hooks.attach('after_error_response', set_tb)

def cgitb_log_err():
"""Log cgitb details to the log."""
tb = cgitb.text(sys.exc_info())
def set_tb():
cherrypy.log(tb)
cherrypy.request.hooks.attach('after_error_response', set_tb)

part of cp_config:
'tools.cgitb_display_err.on': False,
'tools.log_tracebacks.on': False,
'tools.cgitb_log_err.on': True,

cherrypy.tools.cgitb_display_err =
cherrypy.Tool('before_error_response', cgitb_display_err)
cherrypy.tools.cgitb_log_err = cherrypy.Tool('before_error_response',
cgitb_log_err)
cherrypy.engine.subscribe('start_thread', model.db_connect)
cherrypy.quickstart(root, '/', cp_config)

The above turns on the nice cgitb replacement to the standard
traceback logging.

My database model code:

def db_connect(thread_index):
cherrypy.thread_data.db_main = MySQLdb.connect('localhost',
'root', '1etme1n', 'kiosk_mgmt')
cherrypy.thread_data.db_main.autocommit(True)

So when the database does something:

def do_something():
connection = cherrypy.thread_data.db_main
cursor = connection.cursor()
sql = r"""INSERT...."""
params = (a,b,c,....)
cherrypy.log("point a")
cursor.execute(sql, params)

I see "point a" in the log and a traceback. In the current case, I'm
getting a foreign key constraint violation. But the tracebacks in CP's
output are:

[28/Jan/2012:17:29:14] Traceback (most recent call last):
File "C:\Python27\lib\site-packages\cherrypy-3.2.2-py2.7.egg\cherrypy
\_cprequest.py", line 102, in run
hook()
File "C:\Python27\lib\site-packages\cherrypy-3.2.2-py2.7.egg\cherrypy
\_cprequest.py", line 62, in __call__
return self.callback(**self.kwargs)
File "C:\Documents and Settings\Scott Chapman\My Documents\devel\BEHR
\server\cp_utils.py", line 16, in cgitb_log_err
tb = cgitb.text(sys.exc_info())
File "C:\Python27\lib\cgitb.py", line 214, in text
formatvalue=lambda value: '=' + pydoc.text.repr(value))
File "C:\Python27\lib\inspect.py", line 885, in formatargvalues
specs.append(strseq(args[i], convert, join))
File "C:\Python27\lib\inspect.py", line 840, in strseq
return convert(object)
File "C:\Python27\lib\inspect.py", line 882, in convert
return formatarg(name) + formatvalue(locals[name])
KeyError: 'connection'

[28/Jan/2012:17:29:14] Traceback (most recent call last):
File "C:\Python27\lib\site-packages\cherrypy-3.2.2-py2.7.egg\cherrypy
\_cprequest.py", line 575, in run
self.respond(pi)
File "C:\Python27\lib\site-packages\cherrypy-3.2.2-py2.7.egg\cherrypy
\_cprequest.py", line 676, in respond
self.handle_error()
File "C:\Python27\lib\site-packages\cherrypy-3.2.2-py2.7.egg\cherrypy
\_cprequest.py", line 749, in handle_error
self.hooks.run("before_error_response")
File "C:\Python27\lib\site-packages\cherrypy-3.2.2-py2.7.egg\cherrypy
\_cprequest.py", line 112, in run
raise exc
KeyError: 'connection'

The connection is defined in the local scope of the procedure (we
fetch a cursor from it no problem).

I'm not at all clear why this is doing this. Of course this makes
debugging database issues more fun.

Any clues?

Scott

[Michiel Overtoom]

On Jan 29, 2012, at 03:00, Scott Chapman wrote:

> I'm not at all clear why this is doing this. Of course this makes
> debugging database issues more fun.

I see you're using MySQL as a database, and undoubtly the underlying libmysql at some point. Libmysql is not threadsafe, and CherryPy is threaded. In my case that gave problems (segfaults!) and I had to use something like DBUtils to get around that. I'm not sure this is applicable to your situation.

Greetings,

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