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Key: MODPYTHON-127
Type: Improvement Improvement
Status: Closed Closed
Resolution: Fixed
Priority: Major Major
Assignee: Graham Dumpleton
Reporter: Graham Dumpleton
Votes: 0
Watchers: 0
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mod_python

Use namespace for mod_python PythonOption settings.

Created: 10/Feb/06 07:30 AM   Updated: 05/Apr/07 11:48 AM
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Component/s: core
Affects Version/s: 3.3.x
Fix Version/s: 3.3.1

Time Tracking:
Not Specified

Resolution Date: 27/Oct/06 08:45 AM


 Description  « Hide
In the interests of avoiding name clashes, I want to push that where mod_python uses its own PythonOption settings, that they use a namespace. For example:

    PythonOption mod_python.session_cookie_name ...
    PythonOption mod_python.ApplicationPath ...
    PythonOption mod_python.session_dbm ...
    PythonOption mod_python.session_fast_cleanup ...
    etc ....

If appropriate for mod_python, multiple levels of naming should be used. For example, "session_fast_cleanup" is actually related to FileSession, so perhaps it should be:

  PythonOption mod_python.Session.cookie_name ...
  PythonOption mod_python.Session.application_path ...
  PythonOption mod_python.DbmSession.database ...
  PythonOption mod_python.FileSession.fast_cleanup ...

Thus, class name is interjected as second level in name. Also would like to see final attribute name settle on lower case with underscore between distinct words.

We can support old names in mod_python for the time being but should deprecate them.

Any third party package developers should be strongly encouraged to also put any of their own PythonOption settings names in their own unique namespace.

Mailing list thread where this was first proposed, and in case there were followups of interest, was:

  http://www.modpython.org/pipermail/mod_python/2006-February/020213.html



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Graham Dumpleton added a comment - 29/Mar/06 01:52 PM
Here is the list of options that I can find and some suggestions as to what they be called instead. Remember that old options will be honoured for backward compatibility with threat of them later being deprecated.

psp.py

  # class PSP

  PSPDbmCache ==> mod_python.PSP.cache_database_filename

Session.py

  # class BaseSession

  session_cookie_name ==> mod_python.BaseSession.cookie_name
  ApplicationPath ==> mod_python.BaseSession.application_path

  # class DbmSession

  session_dbm ==> mod_python.DbmSession.database_filename
  session_directory ==> mod_python.DbmSession.database_directory

  # class FileSession

  session_fast_cleanup ==> mod_python.FileSession.enable_fast_cleanup
  session_verify_cleanup ==> mod_python.FileSession.verify_session_timeout
  session_grace_period ==> mod_python.FileSession.cleanup_grace_period
  session_cleanup_time_limit ==> mod_python.FileSession.cleanup_time_limit
  session_directory ==> mod_python.FileSession.database_directory

  # class Session

  session ==> mod_python.Session.session_type

Anyone like to confirm that this is all and validate that names reasonable or suggest better names. My choices of names for FileSession, although they now have a name which is clearer to me, mean they diverge from what class initialiser variable names were. If all session types derive from BaseSession, should the existance of the BaseSession class be hidden and mod_python.Session.* be used instead of cases where list mod_python.BaseSession.*?

Note that an interesting issue deriving from making this list is that both DbmSession and FileSession use the "session_directory" option at the moment. Could a conflict arise from doing this if they are both writing to the same directory?

Feedback?

Jim Gallacher added a comment - 30/Mar/06 02:11 AM
I've scanned the source and I think you have caught all the instances that need changing.

Are we sure we want to use CamelCase in the option names? I think this may be confusing if there is not a 1:1 correspondence between the PythonOption key and actual module namespace. So should it be

    mod_python.FileSession.some_option
or
   mod_python.session.FileSession.some_option?

I'd rather not use CamelCase if we don't have a 1:1 mapping between the PythonOption key and the fully qualified class name. So either use
   mod_python.file_session.fast_cleanup
or
    mod_python.session.FileSession.fast_cleanup

I'd avoid using mod_python.BaseSession, and just use mod_python.session for global session options. Using BaseSession just exposes an implementation detail and does not make the intent any clearer. Plus

Again, notice the potential confusion with the camel case. session.Session is a factory function, so should mod_python.Session.some_option only control the behaviour of that function, or is it intended as global option for all session classes? What if a user creates a session instance directly, bypassing session.Session() - should mod_python.Session.some_option still be used?

I think for your proposed changes for the FileSession options are logical and should be adopted. I wonder though if we should refactor the constructor to use the new names as well? It would certainly be easier to do this now as FileSession may not be widely adopted yet. Consistency is a good thing after all.

There is no conflict using session_directory for both DbmSession and FileSession. DbmSession creates a dbm file (/session/directory/mp_sess.dbm) in the directory, while FileSession creates its file hiearchy its own subdirectory (/session/directory/mp_sess/). Of course people are free to use mod_python.DbmSession.database_filename /session/directory/mp_sess to mess things up, but there is not much we can do about that.

My original thinking was that the session directory would be global to any session class that needs it. Should that directory flip back to the default (/tmp) just because I decide to use a different session class? Of course we could have it both ways:

if 'mod_python.session.FileSession.database_directory' in options
   use it
else
  use mod_python.session.database_directory

Graham Dumpleton added a comment - 25/Apr/06 07:52 AM
Okay, lets not use camel case and where a sub namespace is required, it should refer to the concept of what is being implemented as opposed to a specific class name. Thus two general forms would be:

  mod_python.global_option_name
  mod_python.feature_name.sub_option_name

Thus:

psp.py

  # class PSP

  PSPDbmCache ==> mod_python.psp.cache_database_filename

Session.py

  # class BaseSession

  session_cookie_name ==> mod_python.session.cookie_name
  ApplicationPath ==> mod_python.session.application_path

  # class DbmSession

  session_dbm ==> mod_python.dbm_session.database_filename
  session_directory ==> mod_python.dbm_session.database_directory

  # class FileSession

  session_fast_cleanup ==> mod_python.file_session.enable_fast_cleanup
  session_verify_cleanup ==> mod_python.file_session.verify_session_timeout
  session_grace_period ==> mod_python.file_session.cleanup_grace_period
  session_cleanup_time_limit ==> mod_python.file_session.cleanup_time_limit
  session_directory ==> mod_python.file_session.database_directory

  # class Session

  session ==> mod_python.session.session_type

Documentation would state that any option of form mod_python.* is reserved for mod_python use. Documentation should also encourage users when creating add-ons to use their own namespace qualifier and not pollute the global namespace.

In respect of backward compatibility for old option names, although it would be logical to support old names, I would suggest we add an option:

  mod_python.allow_old_option_names

For now this would default to "1" indicating that old names would still be supported. It could though be used to turn off acceptance of old names. Come the next major version, I would suggest the default for this option change to "0" indicating that by default old names would not be accepted. At that time if you really need to use the old names, then you can enable the support.

Graham Dumpleton added a comment - 13/Aug/06 10:13 AM
Lets target this to be done for 3.3. We just need some agreement that proposed names are okay, plus a consensus on how we go about deprecating old names. Do we have an option now which if enabled prohibits use of old names and outputs some sort of warning if they are, or do we do something else?

Graham Dumpleton added a comment - 08/Oct/06 11:46 AM
Have made code changes (not documentation), but not yet committed.

Having done this, I found myself asking whether there should also be a:

  mod_python.session.database_directory

This would be a fallback for when the 'session_database' option against a specific type of session class hasn't been set. Ie., search order would be:

  mod_python.dbm_session.database_directory
  mod_python.session.database_directory
  session_directory # for backward compatibility only

and:

  mod_python.file_session.database_directory
  mod_python.session.database_directory
  session_directory # for backward compatibility only

This would allow session directory to be set once regardless of what type of session class was used. At least, for those which store stuff in the file system, as MemorySession wouldn't use it.

Comments???

Jim Gallacher added a comment - 10/Oct/06 04:24 PM
+1
Your suggestion is logical. Explicit is better than implict.

Jim Gallacher added a comment - 20/Oct/06 04:31 PM
We need to make sure we address this in the unittests as well. Should we have tests for the additional options?

Graham Dumpleton added a comment - 27/Oct/06 08:45 AM
For now I have just made the tests use the new option names. There is obviously a risk that I stuffed up the backward compatibility for old options, but hopefully not. Documentation updated where appropriate.