add sasl auth for kafka

content/scalers/apache-kafka-topic.md

@@ -22,15 +22,31 @@ This specification describes the `kafka` trigger for Apache Kafka Topic.
       brokerList: kafka.svc:9092
       consumerGroup: my-group
       topic: test-topic
-      lagThreshold: '5' # Optional. How much the stream is lagging on the current consumer group
+      lagThreshold: '5'
 ```
 
+**Parameter list:**
+
+- `lagThreshold` Optional. How much the stream is lagging on the current consumer group
+
 ### Authentication Parameters
 
-No authentication required.
+ You can use `TriggerAuthentication` CRD to configure the authenticate by providing authMode, username, password. If your kafka cluster does not have sasl authentication turned on, you will not need to pay attention to it.
+
+**Credential based authentication:**
+
+- `authMode` Kafka sasl auth mode. Optional. The default value is none. For now, it must be one of none, sasl_plaintext, sasl_ssl, sasl_scram_sha256, sasl_scram_sha512.
+- `username` Optional. If authmode is not none, this is required.
+- `password` Optional.If authmode is not none, this is required.
+- `ca` Certificate authority file for TLS client authentication. Optional. If authmode is sasl_ssl, this is required.
+- `cert` Certificate for client authentication. Optional. If authmode is sasl_ssl, this is required.
+- `key` Key for client authentication. Optional. If authmode is sasl_ssl, this is required.
+
 
 ### Example
 
+Your kafka cluster no sasl auth:
+
 ```yaml
 apiVersion: keda.k8s.io/v1alpha1
 kind: ScaledObject
@@ -51,4 +67,69 @@ spec:
       consumerGroup: my-group       # Make sure that this consumer group name is the same one as the one that is consuming topics
       topic: test-topic
       lagThreshold: "50"
+```
+
+Your kafka cluster turn on sasl auth
+
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: keda-kafka-secrets
+  namespace: default
+data:
+  authMode: "sasl_plaintext"
+  username: "admin"
+  password: "admin"
+  ca: <your ca>
+  cert: <your cert>
+  key: <your key>
+---
+apiVersion: keda.k8s.io/v1alpha1
+kind: TriggerAuthentication
+metadata:
+  name: keda-trigger-auth-kafka-credential
+  namespace: default
+spec:
+  secretTargetRef:
+  - parameter: authMode
+    name: keda-kafka-secrets
+    key: authMode
+  - parameter: username
+    name: keda-kafka-secrets
+    key: username
+  - parameter: password
+    name: keda-kafka-secrets
+    key: password
+  - parameter: ca
+    name: keda-kafka-secrets
+    key: ca
+  - parameter: cert
+    name: keda-kafka-secrets
+    key: cert
+  - parameter: key
+    name: keda-kafka-secrets
+    key: key
+---
+apiVersion: keda.k8s.io/v1alpha1
+kind: ScaledObject
+metadata:
+  name: kafka-scaledobject
+  namespace: default
+  labels:
+    deploymentName: azure-functions-deployment
+spec:
+  scaleTargetRef:
+    deploymentName: azure-functions-deployment
+  pollingInterval: 30
+  triggers:
+  - type: kafka
+    metadata:
+      # Required
+      brokerList: localhost:9092
+      consumerGroup: my-group       # Make sure that this consumer group name is the same one as the one that is consuming topics
+      topic: test-topic
+      lagThreshold: "50"
+    authenticationRef:
+      name: keda-trigger-auth-kafka-credential
 ```