extend selenium-grid scaler (#1449)

* describe sessionsPerNode and setSessionsFromHub parameters for selenium-grid scaler

Signed-off-by: Hanzlik, Robert (MONETA) <robert.hanzlik@moneta.cz>

* document sessionBrowserVersion

Signed-off-by: Hanzlik, Robert (MONETA) <robert.hanzlik@moneta.cz>

* Update content/docs/2.16/scalers/selenium-grid-scaler.md

fix typo

Co-authored-by: Jorge Turrado Ferrero <Jorge_turrado@hotmail.es>
Signed-off-by: Robert Hanzlík <robi@junyks.cz>
Signed-off-by: Hanzlik, Robert (MONETA) <robert.hanzlik@moneta.cz>

---------

Signed-off-by: Hanzlik, Robert (MONETA) <robert.hanzlik@moneta.cz>
Signed-off-by: Robert Hanzlík <robi@junyks.cz>
Co-authored-by: Jorge Turrado Ferrero <Jorge_turrado@hotmail.es>

content/docs/2.16/scalers/selenium-grid-scaler.md

@@ -33,9 +33,12 @@ triggers:
 - `browserName` - Name of browser that usually gets passed in the browser capability. Refer to the [Selenium Grid's](https://www.selenium.dev/documentation/en/getting_started_with_webdriver/browsers/) and [WebdriverIO's](https://webdriver.io/docs/options/#capabilities) documentation for more info.
 - `sessionBrowserName` -  Name of the browser when it is an active session, only set if `BrowserName` changes between the queue and the active session. See the Edge example below for further detail. (Optional)
 - `browserVersion` - Version of browser that usually gets passed in the browser capability. Refer to the [Selenium Grid's](https://www.selenium.dev/documentation/en/getting_started_with_webdriver/browsers/) and [WebdriverIO's](https://webdriver.io/docs/options/#capabilities) documentation for more info. (Optional)
+- `sessionBrowserVersion` - Version of the browser when it is an active session, only set, when scaling without defined exact `browserVersion`.
 - `unsafeSsl` - Skip certificate validation when connecting over HTTPS. (Values: `true`, `false`, Default: `false`, Optional)
 - `activationThreshold` - Target value for activating the scaler. Learn more about activation [here](./../concepts/scaling-deployments.md#activating-and-scaling-thresholds). (Default: `0`, Optional)
 - `platformName` - Name of the browser platform. Refer to the [Selenium Grid's](https://www.selenium.dev/documentation/en/getting_started_with_webdriver/browsers/) and [WebdriverIO's](https://webdriver.io/docs/options/#capabilities) documentation for more info. (Default: `Linux`, Optional)
+- `setSessionsFromHub` - When set, count number of browser node slots and sessions from existing nodes, use this data for scaling. (Default: `false`, Optional)
+- `sessionsPerNode` - Use as default number of sessions per browser node, when none are found existing on selenium grid. (Default: `1`, Optional)
 
 ### Example
 
@@ -105,6 +108,29 @@ spec:
         sessionBrowserName: 'msedge'
 ```
 
+If your selenium browser nodes are not exactly same and you wanna to scale them based on real `slots` settings, set `setSessionsFromHub` to `true` and `sessionsPerNode` to real number of slots, if you wanna scale from 0.
+
+```yaml
+apiVersion: keda.sh/v1alpha1
+kind: ScaledObject
+metadata:
+  name: selenium-grid-chrome-scaledobject
+  namespace: keda
+  labels:
+    deploymentName: selenium-chrome-node
+spec:
+  maxReplicaCount: 8
+  scaleTargetRef:
+    name: selenium-chrome-node
+  triggers:
+    - type: selenium-grid
+      metadata:
+        url: 'http://selenium-hub:4444/graphql'
+        browserName: 'chrome'
+        setSessionsFromHub: 'true'
+        sessionsPerNode: 4
+```
+
 If you are supporting multiple versions of browser capability in your Selenium Grid, You should create one scaler for every browser version and pass the `browserVersion` in the metadata.
 
 ```yaml