Monitoring Repositories, as I mentioned one within DevOps Services, are a crucial part of application management in modern systems. Even older or legacy systems can leverage benefits out of a clean, separate system for monitoring, application audits and event connectivity.
There are several stacks available to fulfill this duty; one of them is Elasticsearch, Logstash and Kibana (ELK), which is running on the Apache License 2.0. A brief overview for the license is also provided by the Apache Software Foundation. The single components have the following responsibilities within the stack:
Processing incomming logs.
Store of logs.
Web interface for searching and visualizing logs. It is normally proxied, e.g. via Nginx.
Agent, running on clients, which sends logs to Logtash via the lumberjack networking protocol.