logstash - logstash is a tool for managing events and logs.
nxlog - NXLog offers log management solutions for companies of all sizes.
rsyslog - Rsyslog is an enhanced syslogd supporting, among others, MySQL, PostgreSQL, failover log...
Graylog - Graylog is an open source log management platform for collecting, indexing, and analyzing both structured and unstructured data.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Sentry.io - From error tracking to performance monitoring, developers can see what actually matters, solve quicker, and learn continuously about their applications - from the frontend to the backend.