[Hawkular-dev] Agent - EAP Domain mode support

[John Mazzitelli]

> The question is likely for Mazz, but I wanted to check how we will support the WF domain mode.
> 
> As far as I understand, we are now able to run the agent in the host
> controller but wanted to know a bit more on how we expect the setup to be
> (one agent on the host controller for the whole domain ?)

<TL;DR>
I can run an agent in a host controller, but my main question is: What special functionality are these agents supposed to provide by having them run in the DC or HC (as opposed to running in all the standalone servers?) 
</TL;DR>

Right now, I have the agent at least able to run in a host controller. Each machine where you run your app servers has one host controller on them. Additionally, somewhere in your network, there is a single host controller that is configured to run as the domain controller (i.e. a "domain controller" is just a specially configured host controller - there is only one DC per domain).

We can run the agent today in a host controller (note: I have no agent configuration that tells the agent how to monitor that HC itself - there are not the same subsystems running in a HC than what you see running in a standalone WildFly server).

Do we want to run the agent only in the domain controller? Or do we want to run one agent in each host controller? I suspect we want to do the latter, not the former, simply because it seems to follow the typical way agents are run (one per machine). However, I'm still not clear what it is people want these agents running in a DC or HC to do. What special functionality are these agents supposed to provide by having them run in the DC or HC (as opposed to running in all the standalone servers?)

A different approach to consider is that we can have the host controllers inject agents into the WildFly servers they spawn (so we can then monitor each of the standalone servers that are started by the host controller since each standalone server can get an agents installed via the HC). I am not sure if HCs can actually push out module subsystem extensions like they can deployments - we'd have to ask wildfly-dev. But it would be cool to add the agent subsystem to the domain's profiles so when a HC runs a WildFly server it can not only push out the deployments but also the agent subsystem extension.


> Also I wanted to ask if older versions of the app server could be supported
> or only WF 10 ? (in particular in the context of EAP7/EAP6 support)

I have not tried to run this in a WF9 instance - but alot of this is fairly new in the WF codebase. There was a time when custom subsystem extensions could NOT run in these host controllers - wildfly devs had to add some stuff to get that to work. I suspect (though I do not know for sure) that it won't work on EAP6.