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From Jeff Trawick <traw...@gmail.com>
Subject Re: mutex method configuration cleanup for 2.4
Date Thu, 19 Nov 2009 11:47:56 GMT
On Thu, Nov 19, 2009 at 4:23 AM, Joe Orton <jorton@redhat.com> wrote:
> On Wed, Nov 18, 2009 at 01:18:55PM -0500, Jeff Trawick wrote:
>> A. simplistic goal: Just make it simple for modules with no special
>> issues or love of complexity.  Provide these directives to set global
>> defaults for modules that have been modified to query them:
>>
>> use MutexMethod and MutexFileDir to configure method and lock location
>> globally or for a specific mutex use
>>
>> MutexMethod method-keyword     # "none" not supported as global default
>> MutexFileDir /var/httpd/locks
>>
>> Modules call ap_global_mutex_method() and ap_global_mutex_file_dir()
>> to retrieve that information and use in their APR calls.
>>
>> b. more complex goal: Try to meet requirements of more complex (or
>> configurable) modules to get rid of some of the varying , complex
>> mplementations we already have, as well as handle the simple use.  A
>> rough sketch is shown below:
>
> Yes!  I've looked into doing something like this before and I thought a
> single "Mutex" directive would suffice:
>
> Mutex {default,rewrite-map,...} {none,sysvsem,fcntl:/blah}
>
> where the 3rd arg is parsed by ap_parse_mutex().

"blah" always has to point to a dir, and the lock identifier is used
when constructing the basename.

--/--

I envisioned the conf (perhaps a vendor conf) declaring something like

MutexDir logs
or
MutexDir /var/apache2/2.2/locks

The admin can then adjust the mutex methods as necessary and not worry
about paths to locks.  Or change MutexDir as necessary and not affect
the mutex methods at all.  MutexDir can be used as a preventative
measure even if no file-based mutexes are currently configured.

With the single directive solution, I don't see a way to declare "if
lock files must be used, put them here."

The alternative is something like

# If fcntl-based mutexes are used by default in APR and the locks need to be
# moved to a local directory, uncomment the following and adjust the directory:
# Mutex default fcntl:logs

That works only if the characteristics of specific mutexes aren't
being adjusted by other Mutex directives (but those people deserve
what they get).

Reality check?

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