Feature: Prometheus Metric service widget (#4269)

Co-authored-by: shamoon <4887959+shamoon@users.noreply.github.com>

docs/widgets/services/index.md

@@ -98,6 +98,7 @@ You can also find a list of all available service widgets in the sidebar navigat
 - [Plex](plex.md)
 - [Portainer](portainer.md)
 - [Prometheus](prometheus.md)
+- [Prometheus Metric](prometheusmetric.md)
 - [Prowlarr](prowlarr.md)
 - [Proxmox](proxmox.md)
 - [Proxmox Backup Server](proxmoxbackupserver.md)

docs/widgets/services/prometheusmetric.md

@@ -0,0 +1,67 @@
+---
+title: Prometheus Metric
+description: Prometheus Metric Widget Configuration
+---
+
+Learn more about [Querying Prometheus](https://prometheus.io/docs/prometheus/latest/querying/basics/).
+
+This widget can show metrics for your service defined by PromQL queries which are requested from a running Prometheus instance.
+
+Quries can be defined in the `metrics` array of the widget along with a label to be used to present the metric value. You can optionally specify a global `refreshInterval` in milliseconds and/or define the `refreshInterval` per metric. Inside the optional `format` object of a metric various formatting styles and transformations can be applied (see below).
+
+```yaml
+widget:
+  type: prometheusmetric
+  url: https://prometheus.host.or.ip
+  refreshInterval: 10000 # optional - in milliseconds, defaults to 10s
+  metrics:
+    - label: Metric 1
+      query: alertmanager_alerts{state="active"}
+    - label: Metric 2
+      query: apiserver_storage_size_bytes{node="mynode"}
+      format:
+        type: bytes
+    - label: Metric 3
+      query: avg(prometheus_notifications_latency_seconds)
+      format:
+        type: number
+        suffix: s
+        options:
+          maximumFractionDigits: 4
+    - label: Metric 4
+      query: time()
+      refreshInterval: 1000 # will override global refreshInterval
+      format:
+        type: date
+        scale: 1000
+        options:
+          timeStyle: medium
+```
+
+## Formatting
+
+Supported values for `format.type` are `text`, `number`, `percent`, `bytes`, `bits`, `bbytes`, `bbits`, `byterate`, `bibyterate`, `bitrate`, `bibitrate`, `date`, `duration`, `relativeDate`, and `text` which is the default.
+
+The `dateStyle` and `timeStyle` options of the `date` format are passed directly to [Intl.DateTimeFormat](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DateTimeFormat/DateTimeFormat) and the `style` and `numeric` options of `relativeDate` are passed to [Intl.RelativeTimeFormat](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat/RelativeTimeFormat). For the `number` format, options of [Intl.NumberFormat](https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat/NumberFormat) can be used, e.g. `maximumFractionDigits` or `minimumFractionDigits`.
+
+### Data Transformation
+
+You can manipulate your metric value with the following tools: `scale`, `prefix` and `suffix`, for example:
+
+```yaml
+- query: my_custom_metric{}
+  label: Metric 1
+  format:
+    type: number
+    scale: 1000 # multiplies value by a number or fraction string e.g. 1/16
+- query: my_custom_metric{}
+  label: Metric 2
+  format:
+    type: number
+    prefix: "$" # prefixes value with given string
+- query: my_custom_metric{}
+  label: Metric 3
+  format:
+    type: number
+    suffix: "€" # suffixes value with given string
+```