isolating thread-unsafe modules

Dave Hodgkinson davehodg at
Sun Jul 28 21:13:52 BST 2013

Threads? Now you have two problems. Why not processes?

Sent from my iPhone

On 28 Jul 2013, at 20:07, Bob MacCallum <uncoolbob at> wrote:

> 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.
> Reading symbols from
> .../perl5/x86_64-linux-thread-multi/auto/DBD/Pg/
> Loaded symbols for .../perl5/x86_64-linux-thread-multi/auto/DBD/Pg/
> Reading symbols from
> /usr/local/pgsql_dir/postgresql-8.4.7/lib/ debugging
> symbols found)...done.
> Loaded symbols for /usr/local/pgsql_dir/postgresql-8.4.7/lib/
> Core was generated by `perl bin/'.
> Program terminated with signal 11, Segmentation fault.
> #0  0x00007f9de39e923e in PerlIOEncode_getarg () from
> /usr/lib/perl5/5.12.3/x86_64-linux-thread-multi/auto/PerlIO/encoding/

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