Support connection via unix sockets

[pacohope]

Hi there, this looks like a cool tool.

I have some systems where I have a web server, MariaDB server, and memcached all running on the same VM. To reduce overhead and to improve security, I use Unix sockets to communicate with memcached. I launch memcached like: memcached -s /var/run/memcached/memcached.sock.

When configured to listen on a unix socket, memcached does not use TCP/UDP. So it's not an option to have my web process use the unix socket and have mtop connect via TCP/IP. memcached makes it one or the other.

There is a blog (admittedly 8 years old) that suggests unix sockets perform much faster than TCP/IP to localhost. I intuitively think its probably right, though I haven't performed my own benchmarks.

mtop would need to support unix sockets for me to monitor my memcached processes on these systems. It's not possible to specify /var/run/memcached/memcached.sock on the command line. mtop just tries to look that up as a hostname.

A couple ways to do it. A separate option like -s /path/to/socket where the -s indicates unix sockets, or simply look at what was provided as a hostname. If it begins with a /, interpret it to mean a unix socket, otherwise interpret it to be a hostname.

[56quarters]

Sounds reasonable to me 👍

[56quarters]

Rough plan of the code changes needed for this:

• ServerName needs to be optional on the Server struct
• TcpClientFactory needs to return an error if ServerName is None and --tls-server-name isn't supplied to prevent misuse
• Add a From<Path> implementation for ServerID
• Add a UnixClientFactory for creating clients from Unix sockets
• Add logic to Discovery that creates servers from path-like things
• Add logic anywhere MemcachedClient is created to possibly create a UnixClientFactory
• Most of this needs to be gated behind Unix-only compile flags