qpsmtpd

check_system_load

This plugin is designed to refuse incoming connections with an error message if the system load is above a configurable threshold.

The threshold may be specified as follows:

echo 5 > /etc/qpsmtpd/max_system_load

With this in place if the system load exceeds or equals 5 then new connections will be disconnected with a temporary error & and human-readable explaination.

The Code

Click here to see the code.

#!/usr/bin/perl -w

=head1 NAME

check_system_load - Is the system too overloaded to accept new connections?

=head1 DESCRIPTION

The B<check_system_load> module determines whether the system load is
above a specifiable level, if so it rejects incoming connections.

=cut

=head1 CONFIG

The configuration of this plugin consists of the file
/etc/qpsmtpd/max_system_load.  Within this number is an integar
value.  If the system load exceeds *or* equals this number then
incoming connections are denied until the load reduces.

=cut

=head1 AUTHOR

Steve Kemp
--
http://mail-scanning.com/


=cut


=begin doc

  Hook the pre-connection phase of the transaction - if the load is
 high we want to know as soon as possible.

=end doc

=cut

use Sys::CpuLoad;


sub hook_pre_connection
{
    my ($self,$transaction,%args) = ( @_ );

    #
    #  Return if the configuration variable isn't present.
    #
    my $max_load = $self->qp->config("max_system_load");
    return DECLINED if ( !defined( $max_load ) );

    #
    #  Get current load.
    #
    my @loads = Sys::CpuLoad::load();
    my $load  = int($loads[0]);

    if ( $load >= $max_load )
    {
        $self->log(LOGINFO, "check_system_load $load > $max_load rejecting connection" );
        return (DENYSOFT_DISCONNECT, "System load too high ($load) please try again later" );
    }

    return DECLINED;
}