Kafka Streams - Apache Kafka: A Distributed Streaming Platform.
Grafana - Data visualization & Monitoring with support for Graphite, InfluxDB, Prometheus, Elasticsearch and many more databases
Apache Flink - Flink is a streaming dataflow engine that provides data distribution, communication, and fault tolerance for distributed computations.
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.
Apache NiFi - An easy to use, powerful, and reliable system to process and distribute data.
Prometheus - An open-source systems monitoring and alerting toolkit.