Extend RabbitMQ scaler to support HTTM management API protocol (kedac…

…ore#123)

content/scalers/rabbitmq-queue.md

@@ -18,16 +18,25 @@ triggers:
     host: RabbitMqHost
     queueLength: '20' # Optional. Queue length target for HPA. Default: 20 messages
     queueName: testqueue
+    includeUnacked: 'true' # Optional, use unacked + ready messages count
+    apiHost: RabbitApiHost # Optional HTTP managemet API endpoint
 ```
 
 The `host` value is the name of the environment variable your deployment uses to get the connection string. This is usually resolved from a `Secret V1` or a `ConfigMap V1` collections. `env` and `envFrom` are both supported.  The resolved host should follow a format like `amqp://guest:password@localhost:5672/vhost`
 
+`apiHost` has the similar format but for HTTP API endpoint, like `https://guest:password@localhost:443/vhostname`. Note it has optional vhost name after the host slash which will be used to scope API request.
+
+By default `includeUnacked` is `false` in this case scaler uses AMQP protocol, requires `host` and only counts messages in the queue and ignores unacked messages.
+If `includeUnacked` is `true` then `host` is not required but `apiHost` is required in this case scaler uses HTTP management API and counts messages in the queue + unacked messages count.
+
 ### Authentication Parameters
 
 Not supported yet.
 
 ### Example
 
+AMQP protocol:
+
 ```yaml
 apiVersion: keda.k8s.io/v1alpha1
 kind: ScaledObject
@@ -45,3 +54,24 @@ spec:
       queueName: testqueue
       queueLength: "20"
 ```
+
+HTTP protocol:
+
+```yaml
+apiVersion: keda.k8s.io/v1alpha1
+kind: ScaledObject
+metadata:
+  name: rabbitmq-scaledobject
+  namespace: default
+spec:
+  scaleTargetRef:
+    deploymentName: rabbitmq-deployment
+  triggers:
+  - type: rabbitmq
+    metadata:
+      includeUnacked: "true"
+      # Required
+      apiHost: RabbitApiHost # references a value of format https://guest:password@localhost:443/vhostname
+      queueName: testqueue
+      queueLength: "20"
+```