Monitoring ELK stack -- best practices: how to monitor "flow activity" for the beats and logstash (filter)?

Dear All, I'm wondering what are the best practices to monitor my Elastic Stack (beat, redis, logstash, Elasticsearch) health and activity. Therefore, I would be happy to hear your experience on this topic.

So far, I'm planning to monitor the hosts and services (linux) with centreon; the elasticsearch health and activity with Marvel Plugin; but for the beats and logstash (filter) I don't have a clue about what is the best solution to monitor the "Flow Activity".

Thansk in advance for you replies.
kr,
O.