concept-app-configuration-event.md

title	description	services	author	ms.author	ms.date	ms.topic	ms.service
Reacting to Azure App Configuration key-value events	Use Azure Event Grid to subscribe to App Configuration events, which allow applications to react to changes in key-values without the need for complicated code.	azure-app-configuration,event-grid	jimmyca	jimmyca	02/20/2020	article	azure-app-configuration

Reacting to Azure App Configuration events

Azure App Configuration events enable applications to react to changes in key-values. This is done without the need for complicated code or expensive and inefficient polling services. Instead, events are pushed through Azure Event Grid to subscribers such as Azure Functions, Azure Logic Apps, or even to your own custom http listener. Critically, you only pay for what you use.

Azure App Configuration events are sent to the Azure Event Grid, which provides reliable delivery services to your applications through rich retry policies and dead-letter delivery. To learn more, see Event Grid message delivery and retry.

Common App Configuration event scenarios include refreshing application configuration, triggering deployments, or any configuration-oriented workflow. When changes are infrequent, but your scenario requires immediate responsiveness, event-based architecture can be especially efficient.

Take a look at Use Event Grid for data change notifications for a quick example.

Available Azure App Configuration events

Event grid uses event subscriptions to route event messages to subscribers. Azure App Configuration event subscriptions can include two types of events:

Event Name	Description
Microsoft.AppConfiguration.KeyValueModified	Fired when a key-value is created or replaced
Microsoft.AppConfiguration.KeyValueDeleted	Fired when a key-value is deleted

Event schema

Azure App Configuration events contain all the information you need to respond to changes in your data. You can identify an App Configuration event because the eventType property starts with "Microsoft.AppConfiguration". Additional information about the usage of Event Grid event properties is documented in Event Grid event schema.

Property	Type	Description
topic	string	Full Azure Resource Manager id of the App Configuration that emits the event.
subject	string	The URI of the key-value that is the subject of the event.
eventTime	string	The date/time that the event was generated, in ISO 8601 format.
eventType	string	"Microsoft.AppConfiguration.KeyValueModified" or "Microsoft.AppConfiguration.KeyValueDeleted".
Id	string	A unique identifier of this event.
dataVersion	string	The schema version of the data object.
metadataVersion	string	The schema version of top-level properties.
data	object	Collection of Azure App Configuration specific event data
data.key	string	The key of the key-value that was modified or deleted.
data.label	string	The label, if any, of the key-value that was modified or deleted.
data.etag	string	For KeyValueModified the etag of the new key-value. For KeyValueDeleted the etag of the key-value that was deleted.

Here is an example of a KeyValueModified event:

[{
  "id": "84e17ea4-66db-4b54-8050-df8f7763f87b",
  "topic": "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/testrg/providers/microsoft.appconfiguration/configurationstores/contoso",
  "subject": "https://contoso.azconfig.io/kv/Foo?label=FizzBuzz",
  "data": {
    "key": "Foo",
    "label": "FizzBuzz",
    "etag": "FnUExLaj2moIi4tJX9AXn9sakm0"
  },
  "eventType": "Microsoft.AppConfiguration.KeyValueModified",
  "eventTime": "2019-05-31T20:05:03Z",
  "dataVersion": "1",
  "metadataVersion": "1"
}]

For more information, see Azure App Configuration events schema.

Practices for consuming events

Applications that handle App Configuration events should follow these recommended practices:

[!div class="checklist"]

• Multiple subscriptions can be configured to route events to the same event handler, so do not assume events are from a particular source. Instead, check the topic of the message to ensure the App Configuration instance sending the event.
• Check the eventType and do not assume that all events you receive will be the types you expect.
• Use the etag fields to understand if your information about objects is still up-to-date.
• Use the sequencer fields to understand the order of events on any particular object.
• Use the subject field to access the key-value that was modified.

Next steps

Learn more about Event Grid and give Azure App Configuration events a try:

• About Event Grid
• How to use Event Grid for data change notifications