Route Blob storage events to a custom web endpoint with Azure CLI

Azure Event Grid is an eventing service for the cloud. In this article, you use the Azure CLI to subscribe to Blob storage events, and trigger the event to view the result.

Typically, you send events to an endpoint that processes the event data and takes actions. However, to simplify this article, you send the events to a web app that collects and displays the messages.

When you complete the steps described in this article, you see that the event data has been sent to the web app.

View subscription event

If you don't have an Azure subscription, create a free account before you begin.

Open Azure Cloud Shell

Azure Cloud Shell is a free, interactive shell that you can use to run the steps in this article. Common Azure tools are preinstalled and configured in Cloud Shell for you to use with your account. Just select the Copy button to copy the code, paste it in Cloud Shell, and then press Enter to run it. There are a few ways to open Cloud Shell:

Select Try It in the upper-right corner of a code block. Cloud Shell in this article
Open Cloud Shell in your browser. https://shell.azure.com/bash
Select the Cloud Shell button on the menu in the upper-right corner of the Azure portal. Cloud Shell in the portal

If you choose to install and use the CLI locally, this article requires that you are running the latest version of Azure CLI (2.0.24 or later). To find the version, run az --version. If you need to install or upgrade, see Install Azure CLI.

If you are not using Cloud Shell, you must first sign in using az login.

Create a resource group

Event Grid topics are Azure resources, and must be placed in an Azure resource group. The resource group is a logical collection into which Azure resources are deployed and managed.

Create a resource group with the az group create command.

The following example creates a resource group named <resource_group_name> in the westcentralus location. Replace <resource_group_name> with a unique name for your resource group.

az group create --name <resource_group_name> --location westcentralus

Create a storage account

Blob storage events are available in general-purpose v2 storage accounts and Blob storage accounts. General-purpose v2 storage accounts support all features for all storage services, including Blobs, Files, Queues, and Tables. A Blob storage account is a specialized storage account for storing your unstructured data as blobs (objects) in Azure Storage. Blob storage accounts are like general-purpose storage accounts and share all the great durability, availability, scalability, and performance features that you use today including 100% API consistency for block blobs and append blobs. For more information, see Azure storage account overview.

Replace <storage_account_name> with a unique name for your storage account, and <resource_group_name> with the resource group you created earlier.

az storage account create \
  --name <storage_account_name> \
  --location westcentralus \
  --resource-group <resource_group_name> \
  --sku Standard_LRS \
  --kind BlobStorage \
  --access-tier Hot

Create a message endpoint

Before subscribing to the topic, let's create the endpoint for the event message. Typically, the endpoint takes actions based on the event data. To simplify this quickstart, you deploy a pre-built web app that displays the event messages. The deployed solution includes an App Service plan, an App Service web app, and source code from GitHub.

Replace <your-site-name> with a unique name for your web app. The web app name must be unique because it's part of the DNS entry.

sitename=<your-site-name>

az group deployment create \
  --resource-group <resource_group_name> \
  --template-uri "https://raw.githubusercontent.com/Azure-Samples/azure-event-grid-viewer/master/azuredeploy.json" \
  --parameters siteName=$sitename hostingPlanName=viewerhost

The deployment may take a few minutes to complete. After the deployment has succeeded, view your web app to make sure it's running. In a web browser, navigate to: https://<your-site-name>.azurewebsites.net

You should see the site with no messages currently displayed.

Enable Event Grid resource provider

If you haven't previously used Event Grid in your Azure subscription, you may need to register the Event Grid resource provider. Run the following command to register the provider:

az provider register --namespace Microsoft.EventGrid

It may take a moment for the registration to finish. To check the status, run:

az provider show --namespace Microsoft.EventGrid --query "registrationState"

When registrationState is Registered, you're ready to continue.

Subscribe to your storage account

You subscribe to a topic to tell Event Grid which events you want to track and where to send those events. The following example subscribes to the storage account you created, and passes the URL from your web app as the endpoint for event notification. Replace <event_subscription_name> with a name for your event subscription. For <resource_group_name> and <storage_account_name>, use the values you created earlier.

The endpoint for your web app must include the suffix /api/updates/.

storageid=$(az storage account show --name <storage_account_name> --resource-group <resource_group_name> --query id --output tsv)
endpoint=https://$sitename.azurewebsites.net/api/updates

az eventgrid event-subscription create \
  --resource-id $storageid \
  --name <event_subscription_name> \
  --endpoint $endpoint

View your web app again, and notice that a subscription validation event has been sent to it. Select the eye icon to expand the event data. Event Grid sends the validation event so the endpoint can verify that it wants to receive event data. The web app includes code to validate the subscription.

View subscription event

Trigger an event from Blob storage

Now, let's trigger an event to see how Event Grid distributes the message to your endpoint. First, let's configure the name and key for the storage account, then we create a container, then create and upload a file. Again, use the values for <storage_account_name> and <resource_group_name> you created earlier.

export AZURE_STORAGE_ACCOUNT=<storage_account_name>
export AZURE_STORAGE_ACCESS_KEY="$(az storage account keys list --account-name <storage_account_name> --resource-group <resource_group_name> --query "[0].value" --output tsv)"

az storage container create --name testcontainer

touch testfile.txt
az storage blob upload --file testfile.txt --container-name testcontainer --name testfile.txt

You have triggered the event, and Event Grid sent the message to the endpoint you configured when subscribing. View your web app to see the event you just sent.

[{
  "topic": "/subscriptions/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/resourceGroups/myrg/providers/Microsoft.Storage/storageAccounts/myblobstorageaccount",
  "subject": "/blobServices/default/containers/testcontainer/blobs/testfile.txt",
  "eventType": "Microsoft.Storage.BlobCreated",
  "eventTime": "2017-08-16T20:33:51.0595757Z",
  "id": "4d96b1d4-0001-00b3-58ce-16568c064fab",
  "data": {
    "api": "PutBlockList",
    "clientRequestId": "d65ca2e2-a168-4155-b7a4-2c925c18902f",
    "requestId": "4d96b1d4-0001-00b3-58ce-16568c000000",
    "eTag": "0x8D4E4E61AE038AD",
    "contentType": "text/plain",
    "contentLength": 0,
    "blobType": "BlockBlob",
    "url": "https://myblobstorageaccount.blob.core.windows.net/testcontainer/testblob1.txt",
    "sequencer": "00000000000000EB0000000000046199",
    "storageDiagnostics": {
      "batchId": "dffea416-b46e-4613-ac19-0371c0c5e352"
    }
  },
  "dataVersion": "",
  "metadataVersion": "1"
}]

Clean up resources

If you plan to continue working with this storage account and event subscription, do not clean up the resources created in this article. If you do not plan to continue, use the following command to delete the resources you created in this article.

Replace <resource_group_name> with the resource group you created above.

az group delete --name <resource_group_name>

Next steps

Now that you know how to create topics and event subscriptions, learn more about Blob storage Events and what Event Grid can help you do: