logstash - logstash is a tool for managing events and logs.
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
rsyslog - Rsyslog is an enhanced syslogd supporting, among others, MySQL, PostgreSQL, failover log...
Logz.io - Logz.io provides log analysis software with alerts, role-based access, unlimited scalability and free ELK apps. Index, search & visualize your log data!
Graylog - Graylog is an open source log management platform for collecting, indexing, and analyzing both structured and unstructured data.
Sumo Logic - Sumo Logic is a secure, purpose-built cloud-based machine data analytics service that leverages big data for real-time IT insights