[tpm] [Fwd: Perl and putative DLL Hell]

[Stuart Watt]

TL;DR: don't use a system perl if you can possibly help it.

My suggestion is: it is never a good idea to use a "system" perl for your
application. The distribution is highly likely to patch it in odd or
unusual ways, and at times you don't want them to. This strategy grew out
of having to deploy on CentOS, but other distributions have the same
challenge, they just aren't quite as terrible. I had misery with a
CentOS-hacked variant of some DBD driver, for example, causing real angst,
which was completely at odds with CPAN, and both arrived and left with OS
updates.

I've tended to use perlbrew to get a specific version, and point my
application/scripts to that, even in production. That has the additional
advantage it can belong to a non-root user which makes maintenance very much
safer. This strategy doesn't play as nicely with, e.g., mod_perl, but
anything that's FastCGI-based works fine. And mod_perl is a can of worms
anyway. Regular scripts also work fine, especially if you are careful with
using, e.g., Probe::Perl to find the *current* binary and had that on if
you are running other scripts so that the shebang doesn't get you. Or point
the shebang to your own perl to get it disconnected from the system perl,
or (better) use /usr/bin/env to find the perl in the shebang.

All the best
Stuart

On Thu, Feb 6, 2020 at 3:15 PM <arocker at vex.net> wrote:

>
> I can'thelp with this, being seriously out of contact for another month.
> Can anyone offer help/advice/suggestions?
>
> ---------------------------- Original Message ----------------------------
> Subject: Perl and putative DLL Hell
> From:    "Dave Collier-Brown" <Dave.Collier-Brown at indexexchange.com>
> Date:    Thu, February 6, 2020 10:05 am
> To:      "Alan Rocker" <arocker at vex.net>
> --------------------------------------------------------------------------
>
> We have an "interesting" problem with perl on Centos 7 and 8. One of my
> colleagues, Jourdain Casale  wrote:
>
> Okay well if 7 is easier we are doing it first and Perl / CPAN / Linux
> dependencies are really bad migrating to 8
> 6 is ancient a lot of CPAN won’t build in 8
> Modules work great but only on the Linux they were built for
> A lot of refactoring and risk in 8 vs 7
>
> Jourdain Casale  9:47 AM
> It’s dependency hell
> Like the Linux Perl equivalents of DLL Hell in windows
>
> We're running Centos 6, and I'd like us to go forward to 8 (8.1, actually)
> but the teams who tried out updating the perl found it really hard on 8,
> and hard enough on 7 that they put it off again and again.
>
> If it's really as hard as they thought, I figure you've heard the
> community talking a lot about it.  I do see some blathering via a google
> search, but nothing as severe as was being reported to Jourdain.
>
> Can you help?
>
> --dave
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-- 

Stuart Watt

Chief Technology Officer

t: +1 416-522-8287 | e: stuart.watt at turalt.com | w: turalt.com
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