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Re: Re: forking and dbi

by djantzen (Priest)
on Dec 12, 2002 at 22:31 UTC ( #219450=note: print w/replies, xml ) Need Help??


in reply to Re: forking and dbi
in thread forking and dbi

Right. Here's a bit of code I used recently to explore these issues. It uses (the very nice) Parallel::ForkManager, although the fundamentals are the same for normal forking. Since each handle lives in its own process, transactions are unique to each one, which is a boon for efficiency and makes it safe to have multiple users writing to the DB:

#!/usr/bin/perl use strict; use warnings; use Parallel::ForkManager; use constant NUM => shift; # number of children to spawn. my $pfm = new Parallel::ForkManager(NUM); my $id = 0; # a unique id for each process # a sub to be run *from within the parent thread* at child creation. my $init = sub { my ($pid, $ident) = @_; print "++ $ident started, pid: $pid\n"; }; # a sub to be run *from within the parent thread* at child termination +. my $finalize = sub { my ($pid, $exit_code, $ident) = @_; print "-- $ident finalized, pid: $pid\n"; }; # set the subrefs $pfm->run_on_start($init); $pfm->run_on_finish($finalize); # now for the fun bit. for(1..NUM) { # spawn a new process and break to begin the next iteration, as each + # child process will continue the loop but the parent should not. my $pid = $pfm->start(++$id) and next; $main::db = DBI->connect( ... ); # use your specific initializatio +n args # Do your stuff, sit in a loop to service requests, etc. $main::db->commit(); # or rollback, or something depending on condit +ions. $main::db->disconnect(); $pfm->finish(); # exterminate! exterminate! } # make sure we don't leave any zombies roaming about. $pfm->wait_all_children();

Now if you're running 5.8, you may have the option of sharing the database handle between threads, although I haven't been able to test this yet. Probably though you'd want to take advantage of the stringent separation of data between threads so you'd have similar behavior as when forking.

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