docs(jcloud): autoscale docs

docs/fundamentals/jcloud/advanced.md

@@ -42,6 +42,7 @@ executors:
       capacity: on-demand
 ```
 
+(external-executors)=
 ## External executors
 
 You can also expose only the Executors by setting `expose_gateway` to `False`. Read more about {ref}`External Executors <external-executors>`

docs/fundamentals/jcloud/autoscale.md

@@ -0,0 +1,55 @@
+# Autoscaling
+
+JCloud is Kubernetes based and one of the biggest benefits of Kubernetes is the ability to autoscale your applications
+on-demand. In JCloud, autoscaling function is naturally offered as well, so you can maintain the [serverless](https://en.wikipedia.org/wiki/Serverless_computing) deployments in a cost-effective way with no headache of setting the [right number of replicas](https://docs.jina.ai/how-to/scale-out/#scale-out-your-executor) anymore!
+
+### Configurations
+Autoscaling configurations can be specified on per Executor basis using `autoscale` argument in your Flow YAML, such as:
+
+```yaml
+jtype: Flow
+executors:
+  - name: executor1
+    uses: jinahub+docker://Executor1
+    jcloud:
+      autoscale:
+        min: 1
+        max: 2
+        metric: rps
+        target: 50
+```
+
+Below are the configurations explained in detail:
+
+```{note}
+JCloud Autoscaling leverages [Knative](https://knative.dev/docs/), where the configurations are directly supported. For more information, please visit [Knative Autoscaling](https://knative.dev/docs/serving/autoscaling/).
+```
+
+
+| Name   | Default     | Allowed                   | Description                                                      |
+|--------|-------------|---------------------------|------------------------------------------------------------------|
+| min    | 1           | int                       | Minimum number of replicas (0 means serverless)                  |
+| max    | 2           | int                       | Maximum number of replicas (up to 5)                             |
+| metric | concurrency | `concurrency`   /   `rps` | Metric for scaling                                               |
+| target | 100         | int                       | Target number for concurrency/rps after which replicas autoscale |
+
+
+Moreover, we also support using `jinahub+serverless` protocol for Exectuor's `uses` in the Flow YAML to indiciate the enrollment of Autoscaling, such as:
+
+```yaml
+jtype: Flow
+executors:
+  - name: executor1
+    uses: jinahub+serverless://Executor1
+```
+
+Example above will take the following defaults:
+
+| min | max | metric      | target |
+|-----|-----|-------------|--------|
+| 0   | 2   | concurrency | 100    |
+
+### Serverless
+
+After JCloud deployment using the Autoscaling configurations, the Flow serving part is just the same; the only difference you would probably notice is it may take extra seconds
+to handle the initial requests since it may need to scale the deployments behind the scenes. Let JCloud handle the scaling from now on and you should only worry about the code!