isolating thread-unsafe modules

Ashley Hindmarsh ash+perl at
Mon Jul 29 07:54:27 BST 2013

> Message: 3
> Date: Sun, 28 Jul 2013 20:07:59 +0100
> From: Bob MacCallum <uncoolbob at>
> Subject: isolating thread-unsafe modules
> To: " Perl M[ou]ngers" < at>
> Message-ID:
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> Sorry for the Perl question, but I'm a bit out of my depth...
> I have a Dancer app providing a web service, and I have another script
> using the same Dancer config file and db schema (e.g. "use Dancer
> qw/:script/").  This script watches the database (for changes made by the
> web app) and does the "heavy lifting".  Now I want to parallelise the heavy
> lifting with threads and it seems from the core dump and googling that
> DBD::Pg is not thread safe (see the few lines of debugger output below).
> That's fine - I am happy to run only non-database code in my "worker
> threads".  The trouble is that even if I do this, I think the
> threads->create is threading the Dancer globals which include postgres
> schema connections.
> I tried a few "no My::Schema; no DBD::Pg; no Dancer ..." declarations in
> the block with the threads->create - but that didn't seem to help.
> Does anyone know how I can use thread-safe and thread-unsafe code in the
> same script?  I think I just need to make a block where none of the
> Dancer/database stuff is in scope?
> I thought Thread::Isolate might help, but it hangs on the first test during
> the install.  It's dated 2005.
> thanks!
> Bob.
Does anyone use 'forks'?

CPAN: "drop-in replacement for Perl threads using fork()"


It looks like it might do the trick, but I've never had cause to use it.


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