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Event Grid on Kubernetes - event filtering for subscriptions

  • Article

Event Grid on Kubernetes allows specifying filters on any property in the json payload. These filters are modeled as set of AND conditions, with each outer condition having optional inner OR conditions. For each AND condition, you specify the following values:

  • OperatorType - The type of comparison.
  • Key - The json path to the property on which to apply the filter.
  • Value - The reference value against which the filter is run (or) Values - The set of reference values against which the filter is run.

Important

Event Grid on Kubernetes with Azure Arc is currently in public preview. This preview version is provided without a service level agreement, and it's not recommended for production workloads. Certain features might not be supported or might have constrained capabilities. For more information, see Supplemental Terms of Use for Microsoft Azure Previews.

Filter by event type

By default, all event types (type attribute) for the event source are sent to the endpoint. You can decide to send only certain event types to your endpoint. The JSON syntax for filtering by event type is:

"filter": {
  "includedEventTypes": [
    "orderCreated",
    "orderUpdated"
  ]
}

In the above example, the only events of type orderCreated and orderUpdated events are sent to the subscriber endpoint.

Here's a sample event:

[{
      "specVersion": "1.0",
      "type" : "orderCreated",
      "source": "myCompanyName/us/webCommerceChannel/myOnlineCommerceSiteBrandName",
      "id" : "eventId-n",
      "time" : "2020-12-25T20:54:07+00:00",
      "subject" : "account/acct-123224/order/o-123456",
      "dataSchema" : "1.0",
      "data" : {
         "orderId" : "123",
         "orderType" : "PO",
         "reference" : "https://www.myCompanyName.com/orders/123"
      }
}]

Filter by subject

For simple filtering by subject, specify a starting or ending value for the subject. The JSON syntax for filtering by subject is:

"filter": {
  "subjectBeginsWith": "/account/acct-123224/"
}

For example, the filter configured above will send all orders associated with the account acct-123224 to the subscriber endpoint.

When publishing events to topics, create subjects for your events in a way that make it easy for subscribers to know whether they're interested in the event. Subscribers use the subject property to filter and route events. Consider adding the path where the event happened, so subscribers can filter by segments of that path. The path enables subscribers to narrowly or broadly filter events. If you provide a three segment path like /A/B/C in the subject, subscribers can filter by the first segment /A to get a broad set of events. Those subscribers get events with subjects like /A/B/C or /A/D/E. Other subscribers can filter by /A/B to get a narrower set of events.

Filter by values in event data

See Advanced filtering section in the Event Grid on Azure article to learn about advanced filtering in detail. The following features and operators aren't supported by Event Grid on Kubernetes.

  • Filtering on array data in keys of incoming events
  • Allow filtering on CloudEvents extensions context attributes.
  • Following operators
    • StringNotContains
    • StringNotBeginsWith
    • StringNotEndsWith
    • NumberInRange
    • NumberNotInRange
    • IsNullOrUndefined
    • IsNotNull

Next steps

To learn about destinations and handlers supported by Event Grid on Azure Arc for Kubernetes, see Event Grid on Kubernetes - Event handlers.