Juju nrpe charm sets load alert threshold values incorrectly

[Mian]

There are 2 defects with Juju nrpe charm

1. Config's description of load was not updated to date and is misleading when set to auto
Definition per [1]:
if 'auto' is set, then NUM_CPUS*0.7 is used for the warning threshold and NUM_CPUS for critical
Actuality per [2]&testing:
if 'auto' is set, then load average (1 minute,5 minutes,15 minutes respectively)
(NUM_CPUS*4, NUM_CPUS*2, NUM_CPUS*1) is used for the warning threshold
(NUM_CPUS*8, NUM_CPUS*4, NUM_CPUS*2) is used for the critical threshold

2. If auto is not favourable in the cloud, hard-coded setting is rigid and inflexible
As the customer complained
"The other problem is that if I want to override these numbers in the juju config I can only specify it in the format "-w 8,8,8 -c 15,15,15" and this does not take into account numcpu. Since some units have 88 cores (e.g. nova-compute-kvm) and other have 2 (e.g. kibana) it makes it impossible to set one load number that is appropriate for all systems."

How to reproduce

1. Deploy nrpe and relevant relationships with Juju
$ juju deploy ubuntu
$ juju deploy nrpe
$ juju deploy nagios
$ juju add-relation ubuntu nrpe
$ juju add-relation nrpe:monitors nagios:monitors
$ juju config nrpe load=auto

2. reboot ubuntu node by allocating it with 1/2/3 CPU cores, and check the check_load configuration

First boot with 1 CPU core
root@6nova:~# more /etc/nagios/nrpe.d/check_load.cfg ;cat /proc/cpuinfo | grep processor
# System Load (sub)
command[check_load]=/usr/lib/nagios/plugins/check_load -w 4,2,1 -c 8,4,2
processor : 0

Second boot with 2 CPU core2
root@6nova:~# more /etc/nagios/nrpe.d/check_load.cfg ;cat /proc/cpuinfo | grep processor
# System Load (sub)
command[check_load]=/usr/lib/nagios/plugins/check_load -w 8,4,2 -c 16,8,4
processor : 0
processor : 1
root@6nova:~#

Third boot with 3 CPU cores
root@6nova:~# more /etc/nagios/nrpe.d/check_load.cfg ;cat /proc/cpuinfo | grep processor
# System Load (sub)
command[check_load]=/usr/lib/nagios/plugins/check_load -w 12,6,3 -c 24,12,6
processor : 0
processor : 1
processor : 2
root@6nova:~#

3. hard-coded setting, below setting will be refreshed to all nodes without consideration of number of CPU cores
$ juju config nrpe load="-w 1.0,0.80,0.70 -c 5,2,1"

[1] https://jujucharms.com/nrpe/49
[2] https://git.launchpad.net/nrpe-charm/commit/?id=009a1ae855fe9e4d648ac800b5e7d78a4efb00a6

[Aurelien Lourot (aurelien-lourot)]

1. Documentation of 'auto' has been fixed meanwhile.
2. Complaint about rigidity of the 'load' config is still valid.

[Brett Milford (brettmilford)]

Check load has the parameter:
 -r, --percpu
    Divide the load averages by the number of CPUs (when possible)

Thus in the case of 2) one may still set thresholds a a proportion of the core count i.e.
'-r -w 0.9,0.8,0.7 -c 1.5,1.2,1'