using threads on perl/tk to avoid window freeze/not responding

Question

I am trying to use threading in my perl/tk application so that it won't freeze while connecting to a remote mysql server.

#!/usr/bin/perl
use warnings;
use strict;
use DBI;
use DBD::mysql;
use Tk;
use threads;
use threads::shared;

our $type="mysql";
our $database="b_db";
our $host="mysite.com";
our $port="3306";
our $tablename="tc";
our $user="example";
our $pwd="********";
our $dsn="dbi:$type:$database:$host:$port";

my $thr=threads->create(\&con);

our $mw=new MainWindow;
$mw->Button(-text=>"Connect",-command=>\&con)->pack;
MainLoop; 
sub con{
    our $connect=DBI->connect($dsn,$user,$pwd)or die &mysql_Err;
    print "done connecting\n" if $connect;
    print "error\n" unless $connect;
}
$thr->detach;

but it still freezes when it tries to connect. I have tried to use tk/fileevent:

#!/usr/bin/perl
use DBI;
use DBD::mysql;
use Tk;

our $type="mysql";
our $database="b_db";
our $host="mysite.com";
our $port="3306";
our $tablename="tc";
our $user="example";
our $pwd="********";
our $dsn="dbi:$type:$database:$host:$port";

our $mw=new MainWindow;
$mw->Button(-text=>"Connect",-command=>\&con)->pack;

sub con{
    our $connect=DBI->connect($dsn,$user,$pwd)or die &mysql_Err;
    $mw->fileevent($connect, "readable", \&contquery);
}

sub contquery{
    $query="SELECT * FROM products ORDER BY id";
    $queryhandle=$connect->prepare($query);
    $queryhandle->execute;
    $queryhandle->bind_columns(undef, \$product_id, \$price, \$product_name,  \product_type);
    while($queryhandle->fetch()){
        print <<print;
Product Name: $product_name | Type: $product_type | Prict: $price
print
    }
}
MainLoop;

but it still freezes. Can anyone advise me on what might be the reason for this?

Answer 1

See PerlMonks: Tk isn't thread-safe.

1. Create the thread before any Tk widgets are created.
2. Don't touch any Tk objects from the thread, use shared variables for communication.