[FSTORE-1147] Online feature store notification system

docs/user_guides/fs/feature_group/notification.md

@@ -0,0 +1,111 @@
+---
+description: Documentation on how notifications work for feature groups in Hopsworks.
+---
+
+# How notifications work for a Feature Group
+
+## Introduction
+
+Changes to online-enabled feature groups can be captured by listening to events on specified topics.
+This optimizes the user experience by allowing users to proactively make predictions as soon as there is an update on the features.
+
+In this guide you will learn how to enable notifications for online feature groups within Hopsworks, showing examples in HSFS APIs as well as the user interface.
+
+## Prerequisites
+
+Before you begin this guide we suggest you read the [Feature Group](../../../concepts/fs/feature_group/fg_overview.md) concept page to understand what a feature group is and how it fits in the ML pipeline.
+
+### Create notification topic
+
+To begin with, you will need to have a topic where the notifications will be sent.
+To create a topic in Hopsworks you can navigate to the `Kafka` subsection of project `settings` and click on `Add a new topic`.
+
+<p align="center">
+  <figure>
+    <img src="../../../../assets/images/guides/feature_group/manage_kafka.png" alt="Manage Kafka">
+  </figure>
+</p>
+
+After specifying topic details it can be created by clicking on the `Create Topic` button.
+
+<p align="center">
+  <figure>
+    <img src="../../../../assets/images/guides/feature_group/create_kafka_topic.png" alt="Create kafka topic">
+  </figure>
+</p>
+
+## Using HSFS APIs
+
+### Create a Feeature Group with a notification topic
+
+To enable notifications for an online-enabled feature group using the HSFS APIs you need to [create a feature group](./create.md) and set the `notification_topic_name` properties value to the previously created topic.
+
+=== "Python"
+
+    ```python
+    fg = fs.create_feature_group(name="feature_group_name", version=feature_group_version, primary_key=feature_group_primary_keys, online_enabled=True, notification_topic_name="notification_topic_name")
+    ```
+
+### Update Feature Group notification topic
+
+The notification topic name can be changed after the creation of the feature group.
+By setting the `notification_topic_name` value to `None` or empty string notification will be disabled.
+It can take some time for these changes to take place since the onlinefs service internally caches feature groups for a set amount of time.
+
+=== "Python"
+
+    ```python
+    fg.update_notification_topic_name(notification_topic_name="new_notification_topic_name")
+    ```
+
+## Using UI
+
+### Create a Feeature Group with a notification topic
+
+During the creation of the feature group enable online feature serving.
+When enabled you will be able to set the `CDC topic name` property.
+CDC stands for change data capture.
+
+<p align="center">
+  <figure>
+    <img src="../../../../assets/images/guides/feature_group/create_online_enabled_feature_group.png" alt="Create online enabled feature group">
+  </figure>
+</p>
+
+### Update Feeature Group with notification topic
+
+The notification topic name can be changed after creation by editing the feature group.
+By setting the `CDC topic name` value to empty the notifications will be disabled.
+It can take some time for changes to notifications to take place.
+
+<p align="center">
+  <figure>
+    <img src="../../../../assets/images/guides/feature_group/edit_online_enabled_feature_group.png" alt="Edit online enabled feature group">
+  </figure>
+</p>
+
+## Example of notification event
+
+Once properly set up the online feature store service will produce events to the provided notification topic when data ingestion is completed for records.
+
+Here is an example output:
+
+```
+{
+  "projectId":119,
+  "featureStoreId":67,
+  "featureGroupId":14,
+  "entry":{
+    "id":"15",
+    "text":"test"
+  },
+  "featureViews":[
+    {
+      "id":9,
+      "name":"test",
+      "version":1,
+      "featurestoreId":67
+    }
+  ]
+}
+```

mkdocs.yml

@@ -73,6 +73,7 @@ nav:
               - Create: user_guides/fs/feature_group/create.md
               - Create External: user_guides/fs/feature_group/create_external.md
               - Deprecating: user_guides/fs/feature_group/deprecation.md
+              - Notification: user_guides/fs/feature_group/notification.md
               - Data Types and Schema management: user_guides/fs/feature_group/data_types.md
               - Statistics: user_guides/fs/feature_group/statistics.md
               - Data Validation: user_guides/fs/feature_group/data_validation.md