Multisite real time monitoring

Hello,

We have multisite with around 500 sites.
http://ln.fixdigital.co.il
The multisite works on VPS with Nginx and php7

Many times we have CPU/traffic load problems.

I want to know whats the preferred tools to monitor the multisite load in real time.
1. To monitor the traffic per domain in real time.
2. To monitor CPU load per domain in real time.

Andrey.