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Reacting to Azure App Configuration events

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  • 3 minutes to read

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. For more information, 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.

Diagram that shows Event Grid Model.

Available event types

Event Grid uses event subscriptions to route event messages to subscribers. Azure App Configuration emits the following event types:

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

Event schema

An event has the following top-level data:

Property Type Description
topic string Full resource path to the event source. This field isn't writeable. Event Grid provides this value.
subject string Publisher-defined path to the event subject.
eventType string One of the registered event types for this event source.
eventTime string The time the event is generated based on the provider's UTC time.
id string Unique identifier for the event.
data object App Configuration event data.
dataVersion string The schema version of the data object. The publisher defines the schema version.
metadataVersion string The schema version of the event metadata. Event Grid defines the schema of the top-level properties. Event Grid provides this value.

The data object has the following properties:

Property Type Description
key string The key of the key-value that was modified or deleted.
label string The label, if any, of the key-value that was modified or deleted.
etag string For KeyValueModified the etag of the new key-value. For KeyValueDeleted the etag of the key-value that was deleted.

Example event

The following example shows the schema of a key-value modified 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"
}]

The schema for a key-value deleted event is similar:

[{
  "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.KeyValueDeleted",
  "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:

  • Multiple subscriptions can be configured to route events to the same event handler, so don't assume events are from a particular source. Instead, check the topic of the message to ensure that the App Configuration instance is sending the event.
  • Check the eventType, and don't 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

To learn more about Event Grid and to give Azure App Configuration events a try, see:

About Event Grid

How to use Event Grid for data change notifications