isolating thread-unsafe modules

[Bob MacCallum]

Good question - I have always hacked something with fork in the past but it
just seemed so simple with Thread::Queue and threads.  I've never needed
much IPC in the past.

It looks like this could be a better option:

http://search.cpan.org/~aristotle/Proc-Fork-0.802/lib/Proc/Fork.pm#Multi-child_example

(thanks also to Dominic for the same warning re: threads)



On Sun, Jul 28, 2013 at 9:13 PM, Dave Hodgkinson <davehodg at gmail.com> wrote:

> Threads? Now you have two problems. Why not processes?
>
> Sent from my iPhone
>
> On 28 Jul 2013, at 20:07, Bob MacCallum <uncoolbob at gmail.com> 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/Pg.so...done.
> > Loaded symbols for .../perl5/x86_64-linux-thread-multi/auto/DBD/Pg/Pg.so
> > Reading symbols from
> > /usr/local/pgsql_dir/postgresql-8.4.7/lib/libpq.so.5...(no debugging
> > symbols found)...done.
> > Loaded symbols for /usr/local/pgsql_dir/postgresql-8.4.7/lib/libpq.so.5
> > Core was generated by `perl bin/maintain_populations-threaded.pl'.
> > 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/encoding.so
>
>