Mailing List Archive: ModPerl: Docs-dev

Apache Reload Caveat

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modperl-list at 2xlp

Mar 30, 2006, 3:34 PM

Post #1 of 5 (2837 views)
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Apache Reload Caveat

[. note: i sent this earlier, then realized that i sent it from an
unsubscribed address. i'm resending because i can't remember if
unregistered messages are /dev/nulled or admined in ]

I'm not submitting this as a patch, as I don't know how to properly
word this.

It's pretty much a variation of the following issue, but has to do
with class inheritance

http://perl.apache.org/docs/2.0/api/Apache2/
Reload.html#toc_Problems_with_Scripts_Running_with_Registry_Handlers_tha
t_Cache_the_Code

if you subclass a module to override a few methods, and then decide
to remove a subclassed method (to call off the method in the parent
class instead), you will raise an error instead of calling the parent
method.
if you do a restart, everything works as expected.

to note - this happens in mod_perl handlers -- ( i didn't test under
registry, i'd imagine its the same )

case:
==============

package MyUtils;
sub color { "white" }
1;

package MyUtils::Customized;
sub color { "red" }
1;

sub handler{
my $object = My::Utils::Customized->new();
$r->print( "The color is " . $object->color() )
}

================

returns :
"The color is red"

Now we change My::Utils::Customized;
- sub color { "red" }

And we see:
"Not a code reference at xxxxx "

Restarting Apache we will see as we expect
"The color is white"

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perrin at elem

Mar 30, 2006, 3:42 PM

Post #2 of 5 (2700 views)
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Re: Apache Reload Caveat [In reply to]

On Thu, 2006-03-30 at 18:34 -0500, Jonathan Vanasco wrote:
> if you subclass a module to override a few methods, and then decide
> to remove a subclassed method (to call off the method in the parent
> class instead), you will raise an error instead of calling the parent
> method.
> if you do a restart, everything works as expected.

Perl caches method lookups in order to reduce the performance hit of OO
code. If you'd like to make a patch for the A::Reload docs saying that
it can't handle changes that modify which package a method should be
called in, I think that's close enough.

- Perrin

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modperl-list at 2xlp

Mar 30, 2006, 4:23 PM

Post #3 of 5 (2690 views)
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Re: Apache Reload Caveat [In reply to]

On Mar 30, 2006, at 6:42 PM, Perrin Harkins wrote:

> On Thu, 2006-03-30 at 18:34 -0500, Jonathan Vanasco wrote:
>> if you subclass a module to override a few methods, and then decide
>> to remove a subclassed method (to call off the method in the parent
>> class instead), you will raise an error instead of calling the parent
>> method.
>> if you do a restart, everything works as expected.
>
> Perl caches method lookups in order to reduce the performance hit
> of OO
> code. If you'd like to make a patch for the A::Reload docs saying
> that
> it can't handle changes that modify which package a method should be
> called in, I think that's close enough.
>
> - Perrin

OK. I'll do that and quote from above. Thanks.

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modperl-list at 2xlp

Mar 31, 2006, 10:25 AM

Post #4 of 5 (2697 views)
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Re: Apache Reload Caveat [In reply to]

Attached is a documentation patch that mixes:
my description/example
perrin's explanation

To the Apache2::Reload class inheritance issue i noted.

It *may* be rendered obsolete by a patch the Philip Gollucci
authored, but I can't free up a machine to test his patch until early
next week.

Attachments:

ApacheReloadCaveat.diff (2.19 KB)

pgollucci at p6m7g8

Apr 4, 2006, 12:33 PM

Post #5 of 5 (2677 views)
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Re: Apache Reload Caveat [In reply to]

Jonathan Vanasco wrote:
> Attached is a documentation patch that mixes:
> my description/example
> perrin's explanation
>
> To the Apache2::Reload class inheritance issue i noted.
>
> It *may* be rendered obsolete by a patch the Philip Gollucci authored,
> but I can't free up a machine to test his patch until early next week.
I didn't author that patch... I'm not even enirely sure I've gotten around
to committing it... Though Gozer might have.

I'll dig into this at some point.

Oooh what I wouldn't give for time-suspension machine.

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