sub run_external_command {
    my ( $job, $tid ) = @_;
    $q_PRINT->enqueue( "Thread $tid is running exteral job $job" );
    local( *w_IN, *w_OUT, *w_ERR );
    my $pid = open3( \*w_IN, \*w_OUT, \*w_ERR, '/bin/sleep', int( rand($DEFAULTS->{'random'} ) ) );
    waitpid( $pid, 0 );
    return $DEFAULTS->{'ret_success'};
}