Monitor Nestjs backend - server

Question

In the old days, when we wanted to monitor a "Daemon" / Service, we were asking the software editor the list of all the services running in the background in Windows.
If a "Daemon / service" would be down, it would be restarted.
On top of that, we would use a software like NAGIOS or Centreon to monitore this particular "Daemon / service".
I have a team of Software developper in charge of implementing a nice Nest JS.
Here is what we are going to implement:
2 differents VMs running on a high availability VMWARE cluster with a SAN
the two VMs has Vmotion / High availabity settings
an HA Proxy is setup in order to provide load balancing and additional high availability
Our questions are, how can we detect that :
one of our backend is down ?
one of our backend moving from 50ms average response time to 800ms ?
one of our backend consumes more that 15Gb of ram ?
etc
When we were using "old school" daemon, it was enough, when it comes to JS backend, I am a bit clue less.
Cheers
Kynes
nb : the datacenter in charge of our infrastructure is not "docker / kubernetes / ansible etc compliant)

Answer 1

To be fair, all of these seem doable out of the box for Centreon/Nagios. I'd say check the documentation...
one of our backend is down ?
VM DOWN: the centreon-vmware plugins provides monitoring of VM status.
VM UP but Backend DOWN : use the native http/https url checks provided by Centreon/Nagios to load the web page.
Or use the native SNMP plugins to monitor the status of your node process.
one of our backend moving from 50ms average response time to 800ms ?
Ping Response time: Use the native ping check
Status of the network interfaces of the VM: the centreon-vmware plugin has network interface checks for VMs.
Page loading time: use the native http/https url checks provided by Centreon/Nagios.
You may go even further and use a browser automation tool like selenium to run scenarios on your pages and monitor the time for each step.
one of our backend consumes more that 15Gb of ram ?
Total RAM consumed on server: use the native SNMP memory checks from centreon/nagios.
RAM consumed by a specific process: possible through the native SNMP memory plugin.
Like so:
/usr/lib/centreon/plugins/centreon_linux_snmp.pl --plugin os::linux::snmp::plugin --mode processcount --hostname=127.0.0.1 --process-name="centengine" --memory --cpu
OK: Number of current processes running: 1 - Total memory usage: 8.56 MB - Average memory usage: 8.56 MB - Total CPU usage: 0.00 % | 'nbproc'=1;;;0; 'mem_total'=8978432B;;;0; 'mem_avg'=8978432.00B;;;0; 'cpu_total'=0.00%;;;0;`