Loki is a horizontally-scalable, highly-available, multi-tenant log aggregation system inspired by Prometheus. It is designed to be very cost effective and easy to operate. It does not index the contents of the logs, but rather a set of labels for each log stream.
Grafana has pluggable data source model and comes bundled with rich support for many of the most popular time series databases like Graphite, Prometheus, Elasticsearch, OpenTSDB and InfluxDB. It also has built-in support for cloud monitoring vendors like Google Stackdriver, Amazon Cloudwatch, Microsoft Azure and SQL databases like MySQL and Postgres. Grafana is the only tool that can combine data from so many places into a single dashboard.
Wazuh is a free, open-source host-based intrusion detection system. It performs log analysis, integrity checking, Windows registry monitoring, rootkit detection, time-based alerting, and active response. It provides intrusion detection for most operating systems, including Linux, OpenBSD, FreeBSD, macOS, Solaris and Windows. Wazuh has a centralized, cross-platform architecture allowing multiple systems to be monitored and managed.