Assign a managed identity to an Event Grid custom topic or domain

In the Azure portal, when creating a topic or a domain, you can assign either a system-assigned identity or two user-assigned identities, but not both types of identities. Once the topic or domain is created, you can assign both types of identities by following steps in the Enable identity for an existing topic or domain section.

On the Security page of the topic or domain creation wizard, select Enable system assigned identity.

1. On the Security page of the topic or domain creation wizard, select Add user assigned identity.

2. In the Select user assigned identity window, select the subscription that has the user-assigned identity, select the user-assigned identity, and then click Select.

   

You can also use Azure CLI to create a custom topic or a domain with a system-assigned identity. Currently, Azure CLI doesn't support assigning a user-assigned identity to a topic or a domain.

Use the az eventgrid topic create command with the --identity parameter set to systemassigned. If you don't specify a value for this parameter, the default value noidentity is used.

# create a custom topic with a system-assigned identity
az eventgrid topic create -g <RESOURCE GROUP NAME> --name <TOPIC NAME> -l <LOCATION>  --identity systemassigned

Similarly, you can use the az eventgrid domain create command to create a domain with a system-assigned identity.

When you use Azure portal, you can assign one system assigned identity and up to two user assigned identities to an existing topic or a domain.

The following procedures show you how to enable an identity for a custom topic. The steps for enabling an identity for a domain are similar.

1. Go to the Azure portal.
2. Search for Event Grid topics in the search bar at the top.
3. Select the custom topic for which you want to enable the managed identity.
4. Select Identity on the left menu.

1. In the System assigned tab, turn on the switch to enable the identity.

2. Select Save on the toolbar to save the setting.

   

1. Create a user-assigned identity by following instructions in the Manage user-assigned managed identities article.

2. On the Identity page, switch to the User assigned tab in the right pane, and then select + Add on the toolbar.

   

3. In the Add user managed identity window, follow these steps:

   1. Select the Azure subscription that has the user-assigned identity.
   2. Select the user-assigned identity.
   3. Select Add.

4. Refresh the list in the User assigned tab to see the added user-assigned identity.

You can use similar steps to enable an identity for an Event Grid domain.

You can also use Azure CLI to assign a system-assigned identity to an existing custom topic or domain. Currently, Azure CLI doesn't support assigning a user-assigned identity to a topic or a domain.

Use the az eventgrid topic update command with --identity set to systemassigned to enable system-assigned identity for an existing custom topic. If you want to disable the identity, specify noidentity as the value.

# Update the topic to assign a system-assigned identity. 
az eventgrid topic update -g $rg --name $topicname --identity systemassigned --sku basic 

The command for updating an existing domain is similar (az eventgrid domain update).