target connection count

[isaacs]

Set the target connection count on a sodn.

If the number of connections is below this, then start asking for introductions to FoaFs, until a connection has been attempted with every node in the network.

If the number of connections is too far above this, then end connections, using this heuristic:

1. Never disconnect unless another route to the node can be found.
2. Prefer to sever connections with nodes that have a lot of friends, rather than those that have fewer.
3. Prefer to sever connections with nodes that are more recently connected, rather than those that are older.
4. Prefer to sever connections with nodes that have a longer response-time, rather than those that are faster.

[isaacs]

More thoughts on this:

1. Central "hub" nodes are actually a benefit. The target connection count should be per-node, not per-network. One could imagine multiple different nodes with public IPs that can talk to other nodes behind a firewall on a private network. This is not so different from speaking dnode over socket.io to web browsers -- they are effectively nodes on a private IP that connect to a hub.
2. It would be good to have some role-based stuff, so that a hub could be designated, and have a bunch of workers that spend their cycles doing stuff rather than just being chatty.