Prometheus is an open source metrics-based monitoring and alerting system. In 2016 the Prometheus project became the second member of the Cloud Native Computing Foundation, after Kubernetes. It has a powerful query language(PromQL) with a multidimensional data model suited to store time series data.
The Istio Data Plane is primarily comprised of the Envoy proxies which are attached as dedicated sidecars to each application instance. Istio Data Plane intercepts all incoming(Ingress) and outgoing(Egress) network traffic. This and gives us the ability to apply all the features at this layer, without polluting the application code.