Tag: monitoring

Hey all,

#shortstory

Today I had a pretty interesting task with Icinga2 and Director. The issue was with accessibility to DNS server which was installed in AWS without any public access, so basically it was used only for internal requests. To make story short, the task was to get IP address from local file, hostname from SQL database and assign it to each other.

Here is the changes that I made for ‘PropertyModifierGetHostByName.php’ file.

<?php

// - /usr/share/icingaweb2/modules/director/library/Director/PropertyModifier/PropertyModifierGetHostByName.php
namespace Icinga\Module\Director\PropertyModifier;

use Icinga\Exception\InvalidPropertyException;
use Icinga\Module\Director\Hook\PropertyModifierHook;
use Icinga\Module\Director\Web\Form\QuickForm;

class PropertyModifierGetHostByName extends PropertyModifierHook
{
    public static function addSettingsFormFields(QuickForm $form)
    {
        $form->addElement('select', 'on_failure', array(
            'label'        => 'On failure',
            'description'  => $form->translate('What should we do if the host (DNS) lookup fails?'),
            'multiOptions' => $form->optionalEnum(array(
                'null' => $form->translate('Set no value (null)'),
                'keep' => $form->translate('Keep the property (hostname) as is'),
                'fail' => $form->translate('Let the whole import run fail'),
            )),
            'required'    => true,
        ));
    }

    public function getName()
    {
        return 'Get host by name (DNS lookup)';
    }

    public function transform($value)
    {
        //$host = gethostbyname($value);
        $lines_array = file("/usr/share/icingaweb2/dns.txt"); //comma-separated txt file
        
        foreach($lines_array as $line) {
            if(strpos($line, $value) !== false) {
            list(, $new_str) = explode(",", $line);
            $host = trim($new_str); }
        }

        if (strlen(@inet_pton($host)) !== 4) {
            switch ($this->getSetting('on_failure')) {
                case 'null':
                    return null;
                case 'keep':
                    return $value;
                case 'fail':
                default:
                    throw new InvalidPropertyException(
                        'Host lookup failed for "%s"',
                        $value
                    );
            }
        }

        return $host;
    }
}

The file dns.txt contains IP and domain names, which are comma-separated. You may change the location of the file, use many of them, or even use key-value database for such queries, it’s pretty easy.

So, basically it search for IP address in dns.txt file for provided hostname in Import function. It will return null or fail (based on your settings), if returned IP is not IPv4.

Extra module will be created and pushed to the github on next Monday.

Happy monitoring!