Another part of Nagios that can be extended to fit your needs are notifications. These are messages that Nagios sends out whenever a problem occurs, or is resolved.
One way in which the Nagios notification system can be expanded is to create template-based e-mail sending. This will send notifications as both plain text and HTML messages. The template of the e-mail will be kept in separate files.
We will use two npm libraries: handlebars
(http://handlebarsjs.com) for template processing and emailjs
(https://github.com/eleith/emailjs) for the e-mail sending functionality.
E-mails that contain content in multiple formats need to be wrapped in the multipart/alternative
MIME type. This type will contain two sub-parts—first the plain text version, and following this is the HTML version. This order makes e-mail clients choose HTML over plain text if both the types are supported. For the sake of example, we will ignore plain text.
In the same way as how macro substitution...