Graylog - Graylog is an open source log management platform for collecting, indexing, and analyzing both structured and unstructured data.
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.
Splunk - Splunk's operational intelligence platform helps unearth intelligent insights from machine data.
Sentry - 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.
Kafka - Apache Kafka is publish-subscribe messaging rethought as a distributed commit log.
Grafana - Data visualization & Monitoring with support for Graphite, InfluxDB, Prometheus, Elasticsearch and many more databases