Update Azure Event Grid function subscription with dead-letter storage - azure-eventgrid

Question

I have successfully created an event trigger on storage blob creation, on a storage account called receivingtestwesteurope, under resource group omni-test, which is received via a function called ValidateMetadata. I created this via the portal GUI. However I now want to add deadletter/retry policies, which can only be done via the CLI.
The working trigger is like this:
{
"destination": {
"endpointBaseUrl": "https://omnireceivingprocesstest.azurewebsites.net/admin/extensions/EventGridExtensionConfig",
"endpointType": "WebHook",
"endpointUrl": null
},
"filter": {
"includedEventTypes": [
"Microsoft.Storage.BlobCreated"
],
"isSubjectCaseSensitive": null,
"subjectBeginsWith": "/blobServices/default/containers/snapshots/blobs/",
"subjectEndsWith": ".png"
},
"id": "/subscriptions/fa6409ab-1234-1234-1234-85dd2b3ceab4/resourceGroups/omni-test/providers/Microsoft.Storage/StorageAccounts/receivingtestwesteurope/providers/Microsoft.EventGrid/eventSubscriptions/png",
"labels": [
""
],
"name": "png",
"provisioningState": "Succeeded",
"resourceGroup": "omni-test",
"topic": "/subscriptions/fa6409ab-1234-1234-1234-85dd2b3ceab4/resourceGroups/omni-test/providers/microsoft.storage/storageaccounts/receivingtestwesteurope",
"type": "Microsoft.EventGrid/eventSubscriptions"
}
First I thought I could update the existing event with a deadletter queue:
az eventgrid event-subscription update --name png --deadletter-endpoint receivingtestwesteurope/blobServices/default/containers/eventgrid
Which returns:
az: error: unrecognized arguments: --deadletter-endpoint
receivingtestwesteurope/blobServices/default/containers/eventgrid
Then I tried via REST Patch:
https://learn.microsoft.com/en-us/rest/api/eventgrid/eventsubscriptions/update
scope: /subscriptions/fa6409ab-1234-1234-1234-85dd2b3ceab4/resourceGroups/omni-test/providers/microsoft.storage/storageaccounts/receivingtestwesteurope
eventSubscriptionName: png
api-version: 2018-05-01-preview
Body:
"deadletterdestination": {
"endpointType": "StorageBlob",
"properties": {
"blobContainerName": "eventgrid",
"resourceId": "/subscriptions/fa6409ab-1234-1234-1234-85dd2b3ceab4/resourceGroups/omni-test/providers/microsoft.storage/storageaccounts/receivingtestwesteurope"
}}
Which returns
"Model state is invalid."
===================
Final working solution:
{
"deadletterdestination": {
"endpointType": "StorageBlob",
"properties": {
"blobContainerName": "eventgrid",
"resourceId": "/subscriptions/fa6409ab-1234-1234-1234-85dd2b3ceab4/resourceGroups/omni-test/providers/microsoft.storage/storageaccounts/receivingtestwesteurope"
}
}
}

Answer 1

have a look at Manage Event Grid delivery settings, where in details is described turning-on a dead-lettering. Note, you have to install an eventgrid extension
az extension add --name eventgrid
also, you can use a REST API for updating your event subscription for dead-lettering.
besides that, I have just released my tinny tool Azure Event Grid Tester for helping with an Azure Event Grid model on the local machine.
Update:
The following is a deadletterdestination property:
"deadletterdestination": {
"endpointType": "StorageBlob",
"properties": {
"blobContainerName": "{containerName}",
"resourceId": "/subscriptions/{subscriptionId}/resourceGroups/{resgroup}/providers/Microsoft.Storage/storageAccounts/{storageAccount}"
}
}
you can use the Event Subscriptions - Update (REST API PATCH) with the above property. Note, that the api-version=2018-05-01-preview must be used.