Nagios XI focuses on critical infrastructure monitoring including applications, systems, database, logs, bandwidth, protocol and server performance.
GitLab has a powerful monitoring capability with Prometheus, a time-series monitoring service, providing a flexible platform for monitoring GitLab and other software products. GitLab provides out of the box monitoring with Prometheus, providing easy access to high quality time-series monitoring of GitLab services. GitLab has built-in monitoring that can automatically monitor your deployed applications, with extensive support for native cloud, container, and microservices technology. Additionally, Gitlab uses Jaeger, an open source end-to-end distributed tracing system used for monitoring and troubleshooting microservices-based distributed systems.