docs: Provide Azure Application Insights scaler

content/docs/2.6/scalers/azure-app-insights.md

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+title = "Azure Application Insights"
+layout = "scaler"
+availability = "v2.6+"
+maintainer = "Community"
+description = "Scale applications based on Azure Application Insights metrics."
+go_file = "azure_app_insights_scaler"
++++
+
+### Trigger Specification
+
+This specification describes the `azure-app-insights` trigger that scales based on an Azure Application Insights metric.
+
+```yaml
+triggers:
+- type: azure-app-insights
+  metadata:
+    metricAggregationTimespan: "0:1"
+    metricAggregationType: avg
+    metricFilter: cloud/roleName eq 'role_name'
+    metricId: "customMetrics/example-metric"
+    targetValue: "1"
+    activeDirectoryClientIdFromEnv: CLIENT_ID_ENV_NAME # Optional, can use TriggerAuthentication as well
+    activeDirectoryClientPasswordFromEnv: CLIENT_PASSWORD_ENV_NAME # Optional, can use TriggerAuthentication as well
+    applicationInsightsIdFromEnv: APP_ID # Optional, can use TriggerAuthentication as well
+    tenantIdFromEnv: TENANT_ID` # Optional, can use TriggerAuthentication as well
+```
+
+This scaler is backed by the Azure Application Instance REST API. Please see [this](https://docs.microsoft.com/en-us/rest/api/application-insights/metrics/get) page
+for further details.
+
+**Parameter list:**
+
+- `tenantId` - Id of the tenant that contains the Azure resource. This is used for authentication.
+- `metricId` - The name of the Application Insights metric to query. Use the [Azure Command Line Interface](https://docs.microsoft.com/en-us/cli/azure/install-azure-cli) to run `az monitor app-insights metrics get-metadata` to see a list of available metrics.
+- `targetValue` - Target value to trigger scaling actions.
+- `metricAggregationType` - Aggregation method of the Azure Application Insights metric. The aggregation methods vary from metric to metric. The `az monitor app-insights metrics get-metadata` command can be used to determine which methods apply to a given metric. (Some common aggregation methods are `avg`, `count`, `sum`, `min`, and `max`)
+- `metricAggregationInterval` - Collection time of the metric in format `"hh:mm"`.
+- `applicationInsightsId` - Id of the Application Insights instance to query. This is a GUID that can be retrieved from the Application Insight's `API Access` blade in the Azure Portal.
+- `activeDirectoryClientId` - Id of the Active Directory client. The client must have `Monitoring Reader` permissions for the Application Insights instance.
+- `activeDirectoryClientPassword` - Password of the Active Directory client password.
+- `metricFilter` - Further specify the metrics query using a filter. For example `cloud/roleName eq 'example`. (Optional)
+
+Some parameters can be provided using environment variables, instead of setting them directly in metadata. Here is a list of parameters you can use to retrieve values from environment variables:
+
+- `activeDirectoryClientIdFromEnv` - Name of the environment variable that contains the Id of the Active Directory application. (Optional)
+- `activeDirectoryClientPasswordFromEnv` - Name of the environment variable that contains the Active Directory client password. (Optional)
+- `applicationInsightsIdFromEnv` - Name of the environment variable that contains the Application Insights Id. (Optional)
+- `tenantIdFromEnv` - Name of the environment variable that contains the Id of the tenant that contains the Application Insights instance. (Optional)
+
+### Authentication Parameters
+
+You can use the `TriggerAuthentication` CRD to configure the authentication by providing a set of Azure Active Directory credentials or by using pod identity.
+
+**Credential based authentication:**
+
+- `activeDirectoryClientId` - Id of the Active Directory application which requires at least `Monitoring Reader` permissions.
+- `activeDirectoryClientPassword` - Password of the Active Directory application.
+- `applicationInsightsId` - Id of the Application Insights instance to query.
+- `tenantId` - Id of the tenant that contains the Azure resource.
+
+The principal will need `Monitoring Reader` access to query metrics from the Application Insights instance.
+
+**Pod identity based authentication:**
+
+[Azure Active Directory pod-managed identity](https://docs.microsoft.com/en-us/azure/aks/use-azure-ad-pod-identity) can be used
+in place of credential based authentication. The following section contains an example of a `TriggerAuthentication` using pod identity.
+
+### Example
+
+The following example illustrates the use of a TriggerAuthentication to connect to Application Insights.
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: azure-app-insights-secrets
+data:
+  activeDirectoryClientId: <clientId>
+  activeDirectoryClientPassword: <clientPassword>
+  applicationInsightsId: <appInsightsAppId>
+  tenantId: <tenantId>
+---
+apiVersion: keda.sh/v1alpha1
+kind: TriggerAuthentication
+metadata:
+  name: azure-app-insights-trigger-auth
+spec:
+  secretTargetRef:
+    - parameter: activeDirectoryClientId
+      name: azure-app-insights-secrets
+      key: activeDirectoryClientId
+    - parameter: activeDirectoryClientPassword
+      name: azure-app-insights-secrets
+      key: activeDirectoryClientPassword
+    - parameter: applicationInsightsId
+      name: azure-app-insights-secrets
+      key: applicationInsightsId
+    - parameter: tenantId
+      name: azure-app-insights-secrets
+      key: tenantId
+  # or Pod Identity, kind: Secret is not required in case of pod Identity
+  podIdentity:
+      provider: azure
+---
+apiVersion: keda.sh/v1alpha1
+kind: ScaledObject
+metadata:
+  name: azure-app-insights-scaler
+spec:
+  scaleTargetRef:
+    name: azure-app-insights-example
+  minReplicaCount: 1
+  maxReplicaCount: 10
+  triggers:
+  - type: azure-app-insights
+    metadata:
+      metricId: "customMetrics/example-metric"
+      metricAggregationTimespan: "0:5"
+      metricAggregationType: avg
+      metricFilter: cloud/roleName eq 'example'
+      targetValue: "1"
+    authenticationRef:
+      name: azure-app-insights-trigger-auth
+```
+
+The following example illustrates the use of environment variables to connect to Application Insights.
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: azure-app-insights-secrets
+type: Opaque
+data:
+  activeDirectoryClientId: <clientId>
+  activeDirectoryClientPassword: <clientPassword>
+  applicationInsightsId: <appInsightsAppId>
+  tenantId: <tenantId>
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: azure-app-insights-example
+spec:
+  replicas: 0
+  selector:
+    matchLabels:
+      app: azure-app-insights-example
+  template:
+    metadata:
+      labels:
+        app: azure-app-insights-example
+    spec:
+      containers:
+      - name: example
+        image: nginx:1.16.1
+        env:
+        - name: ACTIVE_DIRECTORY_ID
+          valueFrom:
+            secretKeyRef:
+              name: azure-app-insights-secrets
+              key: activeDirectoryClientId
+        - name: ACTIVE_DIRECTORY_PASSWORD
+          valueFrom:
+            secretKeyRef:
+              name: azure-app-insights-secrets
+              key: activeDirectoryClientPassword
+        - name: APP_INSIGHTS_APP_ID
+          valueFrom:
+            secretKeyRef:
+              name: azure-app-insights-secrets
+              key: applicationInsightsId
+        - name: TENANT_ID
+          valueFrom:
+            secretKeyRef:
+              name: azure-app-insights-secrets
+              key: tenantId
+---
+apiVersion: keda.sh/v1alpha1
+kind: ScaledObject
+metadata:
+  name: azure-app-insights-scaler
+spec:
+  scaleTargetRef:
+    name: azure-app-insights-example
+  pollingInterval: 5
+  cooldownPeriod: 5
+  minReplicaCount: 0
+  maxReplicaCount: 2
+  triggers:
+    - type: azure-app-insights
+      metadata:
+        metricId: "customMetrics/example-metric"
+        metricAggregationTimespan: "0:5"
+        metricAggregationType: avg
+        metricFilter: cloud/roleName eq 'example'
+        targetValue: "1"
+        activeDirectoryClientIdFromEnv: ACTIVE_DIRECTORY_ID
+        activeDirectoryClientPasswordFromEnv: ACTIVE_DIRECTORY_PASSWORD
+        applicationInsightsIdFromEnv: APP_INSIGHTS_APP_ID
+        tenantIdFromEnv: TENANT_ID
+```