Adding dynamodb scaler documentation

content/docs/2.7/scalers/aws-dynamodb.md

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+title = "AWS DynamoDB"
+availability = "v2.7+"
+maintainer = "Community"
+description = "Scale applications based on the records count in AWS DynamoDB"
+layout = "scaler"
+go_file = "aws_dynamodb_scaler"
++++
+
+### Trigger Specification
+
+This specification describes the AWS DynamoDB scaler. This scaler uses a specified DynamoDB query to determine if and when to scale a given workload.
+
+```yaml
+triggers:
+- type: aws-dynamodb
+  metadata:
+    # Required: awsRegion
+    awsRegion: "eu-west-1"
+    # Required: tableName
+    tableName: myTableName
+    # Required: targetValue
+    targetValue: "1"
+    # Required: expressionAttributeNames
+    expressionAttributeNames: '{ "#k" : "partition_key_name"}'
+    # Required: keyConditionExpression
+    keyConditionExpression: "#k = :key"
+    # Required: expressionAttributeValues
+    expressionAttributeValues: '{ ":key" : {"S":"partition_key_target_value"}}'
+    # Optional. Default: pod
+    identityOwner: pod | operator 
+```
+
+**Parameter list:**
+
+- `awsRegion` - AWS Region for the DynamoDB Table.
+- `tableName` - The target table where the scaler execute the query.
+- `targetValue` - The target value for the number of items retrieved by the query.
+- `expressionAttributeNames` - one or more substitution tokens for attribute names in an expression. Defined as JSON.
+- `keyConditionExpression` - the condition that specifies the key values for items to be retrieved by the Query action.
+- `expressionAttributeValues` - one or more values that can be substituted in an expression. Defined as JSON.
+- `identityOwner` - Receive permissions on the DynamoDB Table via Pod Identity or from the KEDA operator itself (see below). (Values: `pod`, `operator`, Default: `pod`, Optional)
+
+> When `identityOwner` set to `operator` - the only requirement is that the KEDA operator has the correct IAM permissions on the DynamoDB Table. Additional Authentication Parameters are not required.
+
+### Authentication Parameters
+
+> These parameters are relevant only when `identityOwner` is set to `pod`.
+
+You can use `TriggerAuthentication` CRD to configure the authenticate by providing either a role ARN or a set of IAM credentials.
+
+**Pod identity based authentication:**
+
+- `podIdentity.provider` - Needs to be set to either `aws-kiam` or `aws-eks` on the `TriggerAuthentication` and the pod/service account must be configured correctly for your pod identity provider.
+
+**Role based authentication:**
+
+- `awsRoleArn` - Amazon Resource Names (ARNs) uniquely identify AWS resource.
+
+**Credential based authentication:**
+
+- `awsAccessKeyID` - Id of the user.
+- `awsSecretAccessKey` - Access key for the user to authenticate with.
+- `awsSessionToken` - Session token, only required when using [temporary credentials](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_temp_use-resources.html).
+
+The user will need access to read properties from the specified AWS SQS queue.
+
+### Example
+
+#### Scaling a deployment using IAM Role
+
+
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: test-secrets
+data:
+  AWS_ROLE_ARN: <encoded-iam-role-arn>
+---
+apiVersion: keda.sh/v1alpha1
+kind: TriggerAuthentication
+metadata:
+  name: keda-trigger-auth-aws-credentials
+  namespace: default
+spec:
+  secretTargetRef:
+  - parameter: awsRoleArn    # The property in KEDA.
+    name: test-secrets       # The name of the kubernetes secret.
+    key: AWS_ROLE_ARN        # The key from the kubernetes secret.
+---
+apiVersion: keda.sh/v1alpha1
+kind: ScaledObject
+metadata:
+  name:  aws-dynamodb-table-scaledobject
+  namespace: keda-test
+spec:
+  scaleTargetRef:
+    name: nginx-deployment
+  triggers:
+  - type: aws-dynamodb
+    authenticationRef:
+      name: keda-trigger-auth-aws-credentials
+    metadata:
+      awsRegion: eu-west-2
+      tableName: keda-events
+      expressionAttributeNames: '{ "#k" : "event_type"}'
+      keyConditionExpression: "#k = :key"
+      expressionAttributeValues: '{ ":key" : {"S":"scaling_event"}}'
+      targetValue: "5"
+```
+
+
+#### Scaling a deployment using IAM Users
+
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: test-secrets
+data:
+  AWS_ACCESS_KEY_ID: <encoded-user-id> # Required.
+  AWS_SECRET_ACCESS_KEY: <encoded-key> # Required.
+  AWS_SESSION_TOKEN: <encoded-session-token> # Required when using temporary credentials.
+---
+apiVersion: keda.sh/v1alpha1
+kind: TriggerAuthentication
+metadata:
+  name: keda-trigger-auth-aws-credentials
+  namespace: default
+spec:
+  secretTargetRef:
+  - parameter: awsAccessKeyID     # Required.
+    name: test-secrets            # Required.
+    key: AWS_ACCESS_KEY_ID        # Required.
+  - parameter: awsSecretAccessKey # Required.
+    name: test-secrets            # Required.
+    key: AWS_SECRET_ACCESS_KEY    # Required.
+  - parameter: awsSessionToken    # Required when using temporary credentials.
+    name: test-secrets            # Required when using temporary credentials.
+    key: AWS_SESSION_TOKEN        # Required when using temporary credentials.
+---
+apiVersion: keda.sh/v1alpha1
+kind: ScaledObject
+metadata:
+  name:  aws-dynamodb-table-scaledobject
+  namespace: keda-test
+spec:
+  scaleTargetRef:
+    name: nginx-deployment
+  triggers:
+  - type: aws-dynamodb
+    authenticationRef:
+      name: keda-trigger-auth-aws-credentials
+    metadata:
+      awsRegion: eu-west-2
+      tableName: keda-events
+      expressionAttributeNames: '{ "#k" : "event_type"}'
+      keyConditionExpression: "#k = :key"
+      expressionAttributeValues: '{ ":key" : {"S":"scaling_event"}}'
+      targetValue: "5"
+```