Re: Is it me or is mod_perl extremely dangerous?

(cc'ing the mod_perl list on this one also, please remember to reply all :)

On Tue, Dec 6, 2011 at 11:28 AM, Dr James A Smith <[email protected]> wrote:
> On 06/12/2011 19:09, Fred Moyer wrote:
>> (cc'ing mod_perl list)
>>
>> On Tue, Dec 6, 2011 at 5:35 AM, Desilets, Alain
>> <[email protected]> wrote:
>>> Thx to Fred, Andre and Jon for answering. BTW: I hope I didn't offend anyone. What I really meant was:
>>
>> No offense taken at all.  Welcome to mod_perl!
>>
>>>
>>>   "Is it me or is mod_perl *much more slippery than standard CGI*?"
>>>
>>> I know that there are lots of folks out there using mod_perl, so I assume it can be used in a safe way. I am just trying to figure out where the slippery patches are, and how easy it will be to slip on them for me, my team, my external collaborators, and even writers of CPAN modules.
>>>
>>> The last point is important. Fred wrote:
>>>
>>> " Most developers find it useful to use CPAN modules which are generally high quality."
>>>
>>> That's what I do also. In fact, I don't think I have ever used a third party module that wasn't from CPAN, and they are, as you say, generally high quality.
>>>
>>> However, even those high quality CPAN modules can fall flat on their face when they are used in contexts that they weren't designed for. For example, I recently discovered that several CPAN modules cannot be used safely in a multithreaded or forked environment. Some of them fail "nicely" (i.e. they KNOW they aren't supposed to be used in this kind of environment and tell you at run time), but others just crash the process upon spawning a new fork or thread, and leave you with no indication as to what caused this. I am concerned that similar issues might arise when using certain CPAN modules in a mod_perl context.
>>>
>>> ---
>>> Question: Is this something that has been known to happen (CPAN modules that don't work well in mod_perl), and if so, how common is it?
>>> ---
>>>
>>> Coming back to where the slippery patches are. Initially, it looked to me that the main thing to watch out for was global variables. By this, I mean variables that can be seen from anywhere in the code. I was OK with that, because I never use global variables, and I have taught everyone in my team to stay away from them. Also, I don't see global variables being used in CPAN modules.
>
> Perl::Critic is your friend in number of places - there are some subtle
> gotchas that people don't realise that are more subtle than the ones
> you mentioned - and perlcritic will point a lot of these out....
>
> In a mod_perl registry script, what is wrong with the following:
>
>  my $user = $self->user_from_cookie( $user_cookie ) if $user_cookie;
>
> ?