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Scales Selenium browser nodes based on number of requests waiting in session queue

Availability: v2.4+ Maintainer: Volvo Cars
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Trigger Specification

This specification describes the selenium-grid trigger that scales browser nodes based on number of requests in session queue and the max sessions per grid.

The scaler creates one browser node per pending request in session queue, divided by the max amount of sessions that can run in parallel. You will have to create one trigger per browser capability that you would like to support in your Selenium Grid.

The below is an example trigger configuration for chrome node.

triggers:  - type: selenium-grid  metadata:  url: 'http://selenium-hub:4444/graphql' # Required. Can be ommitted if specified via TriggerAuthentication/ClusterTriggerAuthentication.  browserName: 'chrome' # Required  browserVersion: '91.0' # Optional. Only required when supporting multiple versions of browser in your Selenium Grid.  unsafeSsl : 'true' # Optional  activationThreshold: 5 # Optional

Parameter list:

  • url - Graphql url of your Selenium Grid. Refer to the Selenium Grid’s documentation here to for more info.
  • browserName - Name of browser that usually gets passed in the browser capability. Refer to the Selenium Grid’s and WebdriverIO’s 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 and WebdriverIO’s documentation for more info. (Optional)
  • 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. (Default: 0, Optional)

Example

Here is a full example of scaled object definition using Selenium Grid trigger:

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'

The above example will create Chrome browser nodes equal to the requests pending in session queue for Chrome browser.

Similarly for Firefox

apiVersion: keda.sh/v1alpha1 kind: ScaledObject metadata:  name: selenium-grid-firefox-scaledobject  namespace: keda  labels:  deploymentName: selenium-firefox-node spec:  maxReplicaCount: 8  scaleTargetRef:  name: selenium-firefox-node  triggers:  - type: selenium-grid  metadata:  url: 'http://selenium-hub:4444/graphql'  browserName: 'firefox'

Similarly for Edge. Note that for Edge you must set the sessionBrowserName to msedge inorder for scaling to work properly.

apiVersion: keda.sh/v1alpha1 kind: ScaledObject metadata:  name: selenium-grid-edge-scaledobject  namespace: keda  labels:  deploymentName: selenium-edge-node spec:  maxReplicaCount: 8  scaleTargetRef:  name: selenium-edge-node  triggers:  - type: selenium-grid  metadata:  url: 'http://selenium-hub:4444/graphql'  browserName: 'MicrosoftEdge'  sessionBrowserName: 'msedge'

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.

apiVersion: keda.sh/v1alpha1 kind: ScaledObject metadata:  name: selenium-grid-chrome-91-scaledobject  namespace: keda  labels:  deploymentName: selenium-chrome-node-91 spec:  maxReplicaCount: 8  scaleTargetRef:  name: selenium-chrome-node-91  triggers:  - type: selenium-grid  metadata:  url: 'http://selenium-hub:4444/graphql'  browserName: 'chrome'  browserVersion: '91.0' 
apiVersion: keda.sh/v1alpha1 kind: ScaledObject metadata:  name: selenium-grid-chrome-90-scaledobject  namespace: keda  labels:  deploymentName: selenium-chrome-node-90 spec:  maxReplicaCount: 8  scaleTargetRef:  name: selenium-chrome-node-90  triggers:  - type: selenium-grid  metadata:  url: 'http://selenium-hub:4444/graphql'  browserName: 'chrome'  browserVersion: '90.0'

Authentication Parameters

It is possible to specify the Graphql url of your Selenium Grid using authentication parameters. This useful if you have enabled Selenium Grid’s Basic HTTP Authentication and would like to keep your credentials secure.

  • url - Graphql url of your Selenium Grid. Refer to the Selenium Grid’s documentation here for more info.
apiVersion: v1 kind: Secret metadata:  name: selenium-grid-secret  namespace: keda type: Opaque data:  graphql-url: base64 encoded value of GraphQL URL --- apiVersion: keda.sh/v1alpha1 kind: TriggerAuthentication metadata:  name: keda-trigger-auth-selenium-grid-secret  namespace: keda spec:  secretTargetRef:  - parameter: url  name: selenium-grid-secret  key: graphql-url --- 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:  browserName: 'chrome'  authenticationRef:  name: keda-trigger-auth-selenium-grid-secret