A relatively new service that so far has been somewhat overlooked by many of the customers I have spoken with, is the Azure Event Grid. Event Grid closely resembles Amazons Simple Notification Service, albeit under the hood they function a little differently.
With the cloud becoming increasingly event-driven, Event Grid has been labelled as the event messaging service for the modern application.
Essentially, the service can be used to intelligently route events between event publishers and event subscribers. Using Event Grid, events generated by Azure resources can be subscribed to, in turn used to trigger a reaction using one of the serverless technologies like Azure Automation or Logic Apps.
The Microsoft graphic above gives a basic representation of the service, including some of the event sources and event handlers available at the time of writing. As with everything in Azure, Microsoft are continuously working behinds the scenes to develop the service further. As such, other event sources and event handlers are planned for later this year include Azure Active Directory, API Management, Azure Data Lake Store, Azure Cosmos DB, Azure Data Factory, and Storage Queues.
For the latest event sources and event handlers refer to the following Microsoft blog
https://docs.microsoft.com/en-gb/azure/event-grid/overview#event-sources
Use cases
Event Grid can be used to develop Serverless Application Architectures, Ops Automation and Application Integration with Ops Automation being the focus of this article.
To give a few examples of how the service might be used for Ops Automation:
- Notifying when Azure resources have been created or changed i.e. Virtual Machines or SQL Databases
- Converting Virtual Machines deployed using unmanaged disks into managed disk machines
- Assigning resource tags to resources when deployed to specific Resource Groups.
Using this style of serverless architecture, opens the door to designing solutions with almost limitless functionality.
Using Event Grid
The remainder of this article steps through implementing a very basic Event Grid deployment. In the demo, every time a Virtual Machine is deployed to a specific Resource Group, Event Grid, using a Webhook, triggers an automation Runbook which sends out email notification.
Assumptions
The following assumptions have been made:
- Azure Automation Account has been created
- Runbook with the required workflow has already been created and published.
The first thing to do is add a Webhook to the Runbook that will be triggered on an event being raised. To do this, browse to the Runbook and from its blade select Webhooks.
Next click + Add Webhook.
Give the Webhook a name and copy its endpoint URL to one side to be used later. Then Click OK to move onto configuring parameters and run settings for the selected Runbook. In my case, I can leave all parameters as default for the purpose of the demo.
Finally go ahead and create the Webhook by clicking the Create button.
The next step is to plumb all the components together, which is done by configuring an Event Grid subscription.
Selecting the Automation Account in which the Runbook we need to trigger is associated, click on Event Grid from the blade of the Automation Accounts overview page.
Click on the + Event Subscription button at the top of the Event Grid window.
Start by giving the subscription a name and then fill in the remaining options. For the purpose of this article, the following configuration was used:
- Topic Type – Azure Subscriptions
- Subscribe to all event types – unchecked
- Event Topics – Resource Write Success selected only
- Subscriber Endpoint – Webhook URL made note of earlier
- Prefix Filter – Location of where the new VMs will be created.
/subscriptions/<subscription-id>/resourcegroups/<resource-group-name>/providers/Microsoft.Compute/virtualMachines
Once all required options have been completed, finally click Create to deploy the subscription.
Now it’s time to test!
Go ahead and create a new Virtual Machine in the Resource Group that was specified in the Event Grid subscription. In my case Production-VMs.
If everything has gone to plan, on completion, a Resource Write Success event was raised which the Event Grid subscription successfully intercepted. This in turn used the Webhook to trigger the Automation Runbook to send out email notification.
In my case the notification was very basic and prepopulated with static content but this could be updated to include Virtual Machine names and other more useful information.
As you can appreciate, this is a very basic example of what the service is capable of when in reality, the sky is the limit!
Pricing
Event Grid price model is based on operation performed, so you only pay for what you use as with many other of the Azure services. Operations can include ingress events, advanced match, delivery attempt and management calls.
- The first 100,000 operations per month are free
- Price per million operations £0.448 *
* Based on West Europe pricing on the 6th April 2018
The only thing to keep in mind is that although more regions will no doubt come online soon. At the time of writing, Event Grid is only available in the following regions:
West US, East US, West US 2, East US 2, West Central US, Central US, West Europe, North Europe, Southeast Asia, and East Asia.
SLA
Guaranteed 99.99% or greater uptime.
For more information on Event Grid checkout the following Microsoft Blog https://docs.microsoft.com/en-gb/azure/event-grid/