I looking for a realtime server monitoring tool and found Netdata is not bad.

Netdata dashboard

NetData is a system for distributed real-time performance and health monitoring. It provides unparalleled insights, in real-time, of everything happening on the system it runs.

Netdata is free, open-source software under GPLv3+ license.  It currently runs on Linux, FreeBSD, and MacOS and designed to run on all systems - physical & virtual servers, containers, IoT. Also it can be integrated to existing monitoring tool chains like Prometheus, Graphite, OpenTSDB, Kafka, Grafana, etc...

Notification has built in supported to alerta.io, amazon sns, discordapp.com, email, flock.com, irc, kavenegar.com, messagebird.com, pagerduty.com, prowl, pushbullet.com, pushover.net, rocket.chat, slack.com, smstools3, syslog, telegram.org, twilio.com, web and custom notifications.

Collection system. Most system related plugins written in C for best performance and most application related plugins written in Python, but actually the plugin can write in any language perl, node.js, java, Go, ruby, PHP even BASH.

It my netdata screen shot, but If you looking for live demo? check out https://my-netdata.io/#demosites

Actually I looking for monitor tool to monitor web servers farms and it cloud work with auto scaling environment. So amount of servers can be up-scale or down-scale anytime. I don't want to manual config this on every servers  (even it possible by automated build). So I use Netdata to centralized data collection and seem work fine.

Pros Cons
Reatime or High resolution metrics Need install agent software
Low hardware resource No auth, need proxy
Zero config, maintenance
Support Notification services

But one thing that I concern is Netdata design for Realtime monitoring. I not sure if it will work well with long time series analysis like Nagios or Zabbix or not?  For example to see data for the past 1 year. However, until we try for a few month then let see is it good enough yet?