Fluentd - Fluentd is a cross platform open source data collection solution originally developed at Treasure Data.
Sentry.io - From error tracking to performance monitoring, developers can see what actually matters, solve quicker, and learn continuously about their applications - from the frontend to the backend.
logstash - logstash is a tool for managing events and logs.
Raygun - Raygun gives developers meaningful insights into problems affecting their applications. Discover issues - Understand the problem - Fix things faster.
Wazuh - Open Source Host and Endpoint Security
Snare - Snare is well known historically as a leader in the event log space.