When relying on various Node.js services (e.g. Butler SOS, Butler, App Duplicator etc), you quickly run into the challenge to ensure all services are always up and running.
A failing service might be fine, as long as it is quickly restarted in a predictable way.
A concrete example could be Qlik Sense or QlikView apps that send status messages to Slack during the execution of their reload scripts. Those messages will fail if Butler is for some reason not running.
This leads us to the conclusion that the services must automatically be
a) started when a server is rebooted, and
b) restarted if they for some reason terminate/die.
Enter process monitors.
At their core, process monitors ensure that the desired processes are always running, i.e. bullet b) above. Some process monitors also offer additional features such as zero-downtime restart of services, memory and performance profiling of the monitored services, being able to monitor different kinds of processes (not only Node.js ditto).
Adding to the pain is the fact that Sense and QlikView runs on Windows servers, meaning that all those great tools available on Linux cannot be used.