Merge pull request #3588 from robertojrojas/document-bindings-directi…

…on-3541

[Bindings] Documents direction Metadata Field

daprdocs/content/en/reference/api/bindings_api.md

@@ -37,6 +37,45 @@ If running on kubernetes apply the component to your cluster.
 
 > **Note:** In production never place passwords or secrets within Dapr component files. For information on securely storing and retrieving secrets using secret stores refer to [Setup Secret Store]({{< ref setup-secret-store >}})
 
+### Binding direction (optional)
+
+In some scenarios, it would be useful to provide additional information to Dapr to indicate the direction supported by the binding component. 
+Providing the supported binding direction helps the Dapr sidecar avoid the `"wait for the app to become ready"` state, where it waits indefinitely for the application to become available.
+
+You can specify the `direction` field as part of the component's metadata. The valid values for this field are: 
+- `"input"`
+- `"output"`
+- `"input, output"`
+
+Here a few scenarios when the `"direction"` metadata field could help:
+
+- When an application (detached from the sidecar) runs as a serverless workload and is scaled to zero, the `"wait for the app to become ready"` check done by the Dapr sidecar becomes pointless.
+
+- If the detached Dapr sidecar is scaled to zero and the application reaches the sidecar (before even starting an HTTP server), the `"wait for the app to become ready"` deadlocks the app and the sidecar into waiting for each other.
+
+### Example
+
+```yaml
+apiVersion: dapr.io/v1alpha1
+kind: Component
+metadata:
+  name: kafkaevent
+spec:
+  type: bindings.kafka
+  version: v1
+  metadata:
+  - name: brokers
+    value: "http://localhost:5050"
+  - name: topics
+    value: "someTopic"
+  - name: publishTopic
+    value: "someTopic2"
+  - name: consumerGroup
+    value: "group1"
+  - name: "direction"
+    value: "input, output"
+```
+
 ## Invoking Service Code Through Input Bindings
 
 A developer who wants to trigger their app using an input binding can listen on a `POST` http endpoint with the route name being the same as `metadata.name`.