Azure Event Grid is a managed event routing service that enables standardized event consumption using a publish-subscribe model.
An event is something that has occurred and is limited to 64KB in Azure. Some examples include
- A new client has signed up with your organization
- A client has initiated a payment that needs to take a specific clearing route
Azure Event Grid supports a number of event sources, an event source is where the event has taken place. Looking at the examples above, these events could have taken place in
- Customer Relationship Management system
- A digital banking channel
Generally, publishers of events send information on a specific end-point or topic and may choose to have an individual topic or multiple topics.
An event subscription is the mechanism that routes events to multiple handlers and subscribers. Subscriptions are also used by handlers to intelligently filter incoming events.
Event handlers is the application or service that processed the event eg. Azure Functions, Event Hubs, Azure Logic Apps or Webhooks.
Various authentication types are provided to support Event Grid such as Webhook event delivery, Event subscriptions & custom topic publishing. RBAC & various action types are also supported to manage and control authorization.
With Webhooks, you can include additional parameters for security such as a secret or an access token that is passed in as a query string. Only HTTPS endpoints are supported.
Custom topics support two types of authentication mechanisms, either a secret key or a shared access signature.
Benefits
- Simple and powerful with easy configuration
- The ability to filter on event types or event publish paths
- A single endpoint can subscribe to many events
- A single endpoint can publish multiple copies to many subscribers
- Can accommodate high throughput (millions per second)
- Consumption based model – pay per event
- Reliable with 24-hour retry capability and exponential backoff
- Many built-in event types
- The flexibility to create custom events
Potential Architectural Patterns
Comparison of messaging services
| Event Grid | Event Hub | Service Bus |
| Reactive Programming | Big data pipeline | High-value enterprise messaging |
| Event distribution (discrete) | Event streaming (series) | Message |
| React to changes | Telemetry & distributed data streaming | Order processing, financial transactions |
Delivery Caveats
- Each message is tried at least once for each subscription
- Events are sent to the registered endpoint of each subscription immediately
- If an endpoint does not acknowledge receipt of an event, Event Grid retries delivery of the event
- You can customize the retry schedule
- If an event is un-deliverable, it is sent to a storage account which in itself is an event source that you can act on