Signed-off-by: Damien Grisonnet <dgrisonn@redhat.com>

Signed-off-by: Damien Grisonnet <dgrisonn@redhat.com>

Previously, prometheus-adapter configuration wasn't taking into account
the scrape interval of kubelet, node-exporter and windows-exporter
leading to getting non fresh results, and even negative results from the
CPU queries when the irate() function was extrapolating data.
To fix that, we want to set the interval used in the irate() function in
the CPU queries to 4x scrape interval in order to extrapolate data
between the last two scrapes. This will improve the freshness of the cpu
usage exposed and prevent incorrect extrapolations.

Signed-off-by: Damien Grisonnet <dgrisonn@redhat.com>

This commit includes windows_exporter metrics in the
node queries for the prometheus adapter configuration.
This will help obtain the resource metrics: memory and
CPU for Windows nodes. This change will also help in
displaying metrics reported through the 'kubectl top'
command which currently reports 'unknown' status for
Windows nodes.

contrib/kube-prometheus: Add section on Prometheus Adapter requirements to README.md