The ELK stack is an open source way to consolidate various logs gathered by logstash to a real-time search, analytics, and visualized form by way of ElasticSearch and Kibana.
From the web site—
- Elasticsearch is a flexible and powerful open source, distributed, real-time search and analytics engine
- Logstash helps you take logs and other time based event data from any system and store it in a single place for additional transformation and processing
- Kibana is Elasticsearch’s data visualization engine, allowing native interaction with all the data in Elasticsearch via custom dashboards. Kibana’s dynamic dashboard panels are savable, shareable and exportable, displaying changes to queries into Elasticsearch in real-time.