Server side debugging of Zope

Created by . Last modified on 2003/08/05.

[Zope] - debugging notes (zope/python/emacs/windows)

Simon Michael [email protected]
Tue, 5 Jan 1999 07:59:37 -0800

Here are some rough notes from my recent zope debugging efforts - I hope
that others will find them useful, or post corrections/improvements.

- Environment: I am using NT Emacs and the cygwin bash shell on windows 98.
So my paths generally have forward slashes.

- I wanted to step through the code of an external method which was not
working. So I tried debugging it with ZPublisher/Test.py, described in the
zope docs. The command line I'm using now is:

$Z/bin/python -i $Z/lib/python/ZPublisher/Test.py -d $Z/lib/python/Main
/files/find_results

python with the '-i' flag is required to get the interactive prompt in an
emacs shell window. Also it ensures that I know exactly which version of
python is being used. $Z is the path to my zope installation.
/files/find_results is the url path to a DTML Document which calls my
external method.

- I could not set a breakpoint on my external method, apparently due to
limitations of the standard pdb class. So I tried stepping right through
zope's execution to that point, but it became clear that I needed a
higher-level tool with good source display. So I explored various
incarnations & versions of debugging tools: pdb, pydb, emacs modes, ddd.
Eventually, I:

- downloaded the latest python, 1.5.2b1. The pdb/bdb/cmd classes in this
version incorporate various enhancements, in particular you can set a
breakpoint in any file which is in your sys.path, as follows:

pdb> import sys
pdb> sys.path.append('/tools/zope/Extensions')
pdb> b ExtranetFind.py:19

- running zope with the latest python gave warnings about API versions.
Things were not working well at the time so for paranoia I copied the new
pdb/bdb/cmd classes into zope's lib/python1.5 and used that. Either version
seems to work fine aside from the warnings.

- I downloaded the latest NT Emacs, 20.3.3.1.1. This fixed some problems,
and has an up-to-date gud.el with pdb support.

- I made a change to .../emacs/lisp/gud.el to get "M-x pdb" to work on
windows:

(defvar gud-pdb-marker-regexp
  "^>
\\([-a-zA-Z0-9_/.:\\]*\\|<string>\\)(\\([0-9]+\\))\\([a-zA-Z0-9_]*\\|\\?\\)(
)\\(->[^\n]*\\)?\n") ;fix for windows/dos pathnames - SKWM

- I downloaded the latest python-mode.el from www.python.org

- I added this in my ~/.emacs to match Test.py's altered pdb prompt
(cosmetic fix):

(add-hook 'pdb-mode-hook '(lambda () (setq comint-prompt-regexp "^pdb> *")))
; for zope debugging

- These made for a more convenient debug prompt:

(eval-after-load "comint" '(define-key comint-mode-map "\M-p"
'comint-previous-matching-input-from-input))
(eval-after-load "comint" '(define-key comint-mode-map "\M-n"
'comint-next-matching-input-from-input))
(eval-after-load "comint" '(define-key comint-mode-map "\C-a" 'comint-bol))
(setq comint-input-ring-size 100)

- NOW, I can step through zope in emacs with full source fontifying, etc
(get help on the "gud-mode" function for keybindings). Type "M-x pdb", and
at the "Run pdb" prompt enter the Test.py command line above.

- In this situation, you can use "python -u" instead of "python -i" to skip
the python prompt at the end of a run.




-Simon

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[Zope] - debugging notes, part 2

Simon Michael [email protected]
Tue, 5 Jan 1999 07:59:45 -0800

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Ok, so now I can debug zope in emacs, and set breakpoints where I want.

Back to the earlier problem! Some breakpoints which I think should get hit,
do not get hit. Eg, a breakpoint on my external method. I don't yet know why
this happens.

*TWO MORE MISC CHANGES:

- So that I could run Test.py with the '-t' flag on windows, I changed
instances of '/dev/null' to '/zopetest.tmp'

- For quicker debugging, I made a change at ExternalMethod/ExternalMethod.py
line 244, to reload external methods every time:

# SKWM - always reload (todo: check debug flag)
#        try: f=self._v_f
#        except: f=self.getFunction()
        f=self.getFunction(1,1)

*SWITCHED TO PDOCUMENTTEMPLATE

- I tried again to step through zope's publishing process and into my
method.. still haven't quite managed it.

- I thought, "well it goes through c code at some point (cDocumentTemplate)
and maybe that's confusing the debugger". Not to mention me. So, in order to
try pDocumentTemplate, I:

- renamed lib/python/DocumentTemplate/cDocumentTemplate.pyd (to hide it);

- changed DT_Util.py:

#SKWM
#except: from pDocumentTemplate import InstanceDict, TemplateDict,
render_blocks
except:
    from pDocumentTemplate import InstanceDict, TemplateDict, render_blocks
    class cDocument: pass

- made a fix, or at least a change, in pDocumentTemplate.py, line 159
(allowed me to manage Documents again) :

#SKWM           r=str(inst)
            r=str(inst)

- And now, zope appears to run fine using the pDocumentTemplate and I can
step through it as far as I want. As before, some breakpoints which I would
expect to get hit, don't.

- With one exception - running with pDocumentTemplate appears to break
access control. Same with BOBO_DEBUG_MODE=1.


On with the battle! Advice welcome!

-Simon

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Hacking on through the zope jungle <chop> <bash> <ouch>
Avoiding a fatal squeeze from certain large snakes <oof>
I wonder if there's an easier trail around here somewhere.

Here are some more brief notes, on the theory that someone may benefit.. or
shoot me before I catch jungle madness..


- PYTHON SETTINGS
I said that "python -u ..." also works when doing "M-x pdb" in emacs. Not
true, stick with "python -i ..." to avoid problems.

Added a whole bunch of zope dirs to the PYTHONPATH environment variable to
allow imports. Works for python 1.5.2b1, but not for zope's python.

- BREAKPOINTS AGAIN
I wrote:
> Ok, so now I can debug zope in emacs, and set breakpoints where I want.

Spoke too soon. pdb's "b filename:lineno" doesn't work. Test.py's fbreak()
function does work. Breakpoints can be configured in a .bobodb file. Eg:

import ExternalMethod
breakpoints = [ExternalMethod.ExternalMethod.__call__,]

Doesn't matter if you use cDocumentTemplate or pDocumentTemplate.

A breakpoint on the external method itself doesn't work. If I step in from
the above, I can then set one that works.

- DEBUGGING IN WEBSERVER MODE
When running in Test.py's command-line mode, the #with statement which calls
my method is initialized but never rendered (why ?). It works fine in normal
webserver mode. I changed Test.py to fire up the whole zopeHTTPserver:

#        db.run('publish_module(file,environ=env,debug=1)',Publish.__dict__,
{'file':file, 'env':env})
        sys.argv = []
        db.run('import serve',Publish.__dict__,{'file':file, 'env':env})

Run Test.py in debug mode with "M-x pdb", as before. It reads breakpoints
from .bobodb (I hardcoded the path to make sure). Continue a few times and
the webserver's running. Access the url with a browser to trigger the
ExternalMethod breakpoint, step into your method and there you are (my holy
grail).


-Simon