is a Java-based open-source log management system which collects, indexes, and analyzes structured or unstructured log data from syslog or any third-party applications Graylog's centralized log management system is designed as a 3-tier architecture which consists of Graylog collector (distributed lightweight log collector for log ingestion), Graylog servers (horizontally-scaling server cluster for log processing and indexing) and centralized web interface (for management, search and visualization). Graylog server relies on Elasticsearch for full-text search and MongoDB
for metadata storage. It also comes with built-in support for alert mechanisms (emails, HTTP callback) for log streams, and user authentication and permissions. Gray servers expose REST APIs to integrate with other external programs (e.g., CLI dashboard, Splunk, Nagios
, Zabbix) for custom alert triggering and log monitoring. The official Graylog website maintains a central repository of community-built plugins, content packs for custom log input/parser/output, other logging libraries and integration guides.