rhtyd commented on pull request #4978:
URL: https://github.com/apache/cloudstack/pull/4978#issuecomment-934173009


   > You are right, this something to be careful about.
   > We've configured the service in a way that it always starts on boot and if 
the process/job is killed for any reason it gets restarted as well. The only 
way of stopping it is via systemd (e.g. systemctl stop 
cloudstack-hahelper.service)
   
   Could you maybe explore systemd itself, there are ways to use dependencies 
and `targets` to ensure the agent is always up and unless explicitly stopped by 
the admin. For example, there's also restart on failure option 
(https://www.freedesktop.org/software/systemd/man/systemd.service.html#Restart=).
   
   > We did not implement such a way of telling that the agent has been 
"intentionally stopped". This would rely on Admins disabling it on the 
CloudStack side.
   > I will need to add some information in the documentation about how to 
handle the cluster with this agent.
   
   See above, most admins may not remember about this feature and I wonder is 
stopping an agent to do maintenance work could cause side-effects. Maybe look 
at my above suggestion on exploiting systemd features. Docs +1
   
   > I can look into a way of adding CA certificates and validate the 
communications. For now, it has no such validation; however, it binds only with 
the node IP in the management network (which in theory is an isolated/secure 
network).
   
   I think if adding a new service for this feature is unavoidable, we should 
absolutely (a) have the service use CA-framework issued certificates to serve 
using secured TLS/SSL certs (i.e. on https), (b) provide a default off option 
(which you've confirmed exists via a cluster-scope global setting), (c) have 
firewall-config enabled when the agent either starts (or the service/process 
starts?) or document on how to use this service (i.e. enable port 8080). 
(Probably not a good idea to expose whole of libvirtd over network, but one 
option may involve just exposing libvirtd over tls/ssh to other neighbour hosts 
https://libvirt.org/remote.html which won't require any additional services).


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