Addon: Use Hostprocess for Windows Exporter (#2048)

* Addon: Use Hostprocess for Windows Exporter #1627

This allows for Windows Exporter to be deployed and configured
dynamically without requiring to specify targets manually for each
Windows node

Documentation and example added

* Addon: Windows Exporter using Hostprocess

Fix some performance issues.
- Specify resource limits for windows exporter.
- Allow for scrape timeout and interval to be configured. Depending
on how many pods are running on a node it can take from 500ms to 15s
to scrape metrics from node. Default timeout is 10s.
- Allow for enabled collectors to be configured.
- Only enable collectors that are being used in rules and dashboards.

* Addon: Windows Exporter using Hostprocess

Fix formatting issues

* Fix formatting issues in windows-hostprocess addon

* Windows Addon: update doc to reflect both configs
- Hostprocess and static

* Windows Addon: update doc

---------

Co-authored-by: Dinesh Sharma <dinesh.sharma@health.telstra.com>

docs/windows.md

@@ -1,8 +1,27 @@
 # Windows
 
-The [Windows addon](../examples/windows.jsonnet) adds the dashboards and rules from [kubernetes-monitoring/kubernetes-mixin](https://github.com/kubernetes-monitoring/kubernetes-mixin#dashboards-for-windows-nodes).
+The [Windows hostprocess addon](../examples/windows-hostprocess.jsonnet) adds the dashboards and rules from [kubernetes-monitoring/kubernetes-mixin](https://github.com/kubernetes-monitoring/kubernetes-mixin#dashboards-for-windows-nodes).
 
-Currently, Docker based Windows does not support running with [windows_exporter](https://github.com/prometheus-community/windows_exporter) in a pod so this add on uses [additional scrape configuration](https://github.com/prometheus-operator/prometheus-operator/blob/master/Documentation/additional-scrape-config.md) to set up a static config to scrape the node ports where windows_exporter is configured.
+It also deploys [windows_exporter](https://github.com/prometheus-community/windows_exporter) as a [hostprocess pod](https://github.com/prometheus-community/windows_exporter/blob/master/kubernetes/kubernetes.md) as Kubernetes now supports HostProcess containers on Windows nodes (as of [v1.22](https://kubernetes.io/blog/2021/08/16/windows-hostprocess-containers/)). The cluster should be using containerd runtime.
+
+```
+local kp = (import 'kube-prometheus/main.libsonnet') +
+  (import 'kube-prometheus/addons/windows-hostprocess.libsonnet') +
+  {
+    values+:: {
+      windowsExporter+:: {
+        image: "ghcr.io/prometheus-community/windows-exporter",
+        version: "0.21.0",
+      },
+    },
+  };
+
+{ ['windows-exporter-' + name]: kp.windowsExporter[name] for name in std.objectFields(kp.windowsExporter) }
+```
+
+See the [full example](../examples/windows-hostprocess.jsonnet) for setup.
+
+If the cluster is running docker runtime then use the other [Windows addon](../examples/windows.jsonnet). The Windows addon does not deploy windows_exporter. Docker based Windows does not support running with [windows_exporter](https://github.com/prometheus-community/windows_exporter) in a pod so this add on uses [additional scrape configuration](https://github.com/prometheus-operator/prometheus-operator/blob/master/Documentation/additional-scrape-config.md) to set up a static config to scrape the node ports where windows_exporter is configured.
 
 The addon requires you to specify the node ips and ports where it can find the windows_exporter. See the [full example](../examples/windows.jsonnet) for setup.
 
@@ -19,5 +38,3 @@ local kp = (import 'kube-prometheus/main.libsonnet') +
     },
   };
 ```
-
-[Containerd](https://github.com/prometheus-community/windows_exporter/blob/master/kubernetes/kubernetes.md) version can run as pod.