[neon-cluster-manager] unix sockets?

[jefflill]

The neon-cluster-manager is currently deployed as local containers on the manager nodes attached to the host network. I'd much rather have this be deployed as a Docker service.

The essential constrains are:

• neon-cluster-manager requires access to the Docker socket
• The Docker socket cannot be exposed outside of the machine without security risks or having to implement complex mutual TLS authentication
• This means that neon-cluster-manager can access Docker via its Unix socket (mounted into the service) or a TCP socket on 127.0.0.1
• .NET Core does not appear to support Unix sockets out-of-the-box
• Docker services cannot be deployed on the host network

The task here is to investigate whether further into .NET Core and Unix sockets:

• Perhaps a URL like http://unix:/var/aspnet/HelloMVC/kestrel.sock would work. This seems like somewhat of a standard in the Linux world.
• Investigate .NET Core/Standard 2.0
• Port/implement an HTTP Handler that works over Unix sockets

[jefflill]

I found some code at https://github.com/Microsoft/Docker.DotNet that implements Unix domain sockets as well as Windows named pipes. I'm going to migrate the domain socket code for now.