Graylog2
www.graylog2.org
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
Graylog2 is an open source log management solution that stores your logs in MongoDB. It consists of a server written in Java that accepts your syslog messages via TCP, UDP or AMQP and stores it in the database. The second part is a web interface that allows you to manage the log messages from your web browser.