Load balance across module connections in v4

[alandekok]

We want to have modules (e.g. radius) open multiple connections, and manage connections to multiple home servers. At the same time, we want to do load-balancing, etc. in the server core, instead of pushing that to the modules.

We can't instantiate multiple versions of the same module, one for each connection / home server. The issue there is that the module instance tree isn't thread-local (tho maybe it should be). Also, if a module clones itself, what does that mean?

i.e. we have:

load-balance {
   radius
}

How will the module tell the parent keyword that there are multiple instances of itself?

One option is to just have the module register keyword-specific callbacks. That way the load-balance keyword can ask the module how many connections it has, and then do load-balancing across those connections.

That does seem somewhat solution-specific tho.

The unlang compile && interpret phase then have to be updated to know about the dynamic number of children, instead of using g->num_children.