Tracking flow information about networks and apps on Linux is something I have been thinking about. I'm wondering how other people are doing it. For networking

Tracking flow information about networks and apps on Linux is something I have been thinking about. I'm wondering how other people are doing it. For networking in general, I suppose you could sample /proc/PID/fd and /proc/PID/net/tcp regular intervals, though it would technically miss some connections. For apps — specifically, microservices — I'm thinking that every app could be modified to emit pairs [from, to] to statsd, which can then be used to transfer the data to a central collector. The downside is that every RPC request has to do this, in all the languages your microservices are written in.