Azure Event Grid vs Event Hub
Tags: azure, tutorial, cloud, devops
Published: 2023-10-07 06:41:08

Azure Event Grid and Azure Event Hub are two services that enable you to build event-driven applications on the cloud. They are both based on the publish-subscribe pattern, but they have some key differences that you should know before choosing one for your scenario. In this blog post, I will explain what each service does, how they differ, and how to create an Azure Event Grid using Azure CLI.

### Azure Event Grid
Azure Event Grid is a service that allows you to route events from any source to any destination. You can use it to react to changes in your Azure resources, such as storage blobs, resource groups, or subscriptions. You can also use it to integrate with third-party services, such as GitHub, Twilio, or SendGrid. Azure Event Grid has a built-in filtering and mapping capability that lets you customize the events that you want to receive and how they are delivered. For example, you can filter events by subject, event type, or data properties. You can also map events to different schemas or formats. Key features include:

1. **Event Publishers and Subscribers:**
 - **Publishers:** Entities that emit events, such as Azure services (e.g., Blob Storage, Azure Active Directory) or custom applications.
 - **Subscribers:** Services or applications that react to events. This can include Azure Functions, Logic Apps, or custom HTTP endpoints.

2. **Event Types:**
 - Supports a wide variety of event types, both Azure-defined and custom events.

3. **Serverless:**
 - Well-integrated with serverless architectures, allowing you to build scalable applications without managing infrastructure.


### Azure Event Hub
Azure Event Hub is a service that allows you to ingest and process large volumes of streaming data. You can use it to capture data from devices, sensors, applications, or logs. Azure Event Hub can handle millions of events per second with low latency and high reliability. You can also use it to analyze and transform the data using Azure Stream Analytics, Azure Functions, or Spark. Azure Event Hub has a partitioning and offset mechanism that lets you control how the data is distributed and consumed. For example, you can partition the data by key or by round-robin. You can also use offsets to track the position of the data in each partition. Key features include:

1. **Event Ingestion:**
 - Efficiently ingests and stores massive amounts of data produced by devices, sensors, or applications.

2. **Event Hubs and Partitions:**
 - Organizes events into Event Hubs, and each hub can have multiple partitions for parallel processing.

3. **Time-series Data:**
 - Suitable for scenarios where the order of events and time-series data are crucial.

### Differences between Azure Event Grid and Azure Event Hub:
The main difference between Azure Event Grid and Azure Event Hub is the type of events that they handle. Azure Event Grid handles discrete events, which are single occurrences that represent a state change or an action. For example, a file being created, a resource being updated, or a message being sent. Azure Event Hub handles telemetry events, which are continuous streams of data that represent measurements or observations. For example, temperature readings, location updates, or click events.

Another difference is the delivery mechanism that they use. Azure Event Grid uses push delivery, which means that it pushes the events to the subscribers as soon as they are available. Azure Event Hub uses pull delivery, which means that the subscribers have to pull the events from the service at their own pace.

### Sample Code to Create an Azure Event Grid Topic using Azure CLI:
To create an Azure Event Grid, you need to have an Azure subscription and an Azure CLI installed on your machine. You also need to have a resource group and a storage account in your subscription. The following steps show how to create an Azure Event Grid using Azure CLI:

1. Log in to your Azure account using `az login`.
2. Create a topic in your resource group using `az eventgrid topic create --name <topic-name> --resource-group <resource-group-name>`.
3. Create a subscription for your topic using `az eventgrid event-subscription create --name <subscription-name> --source-resource-id <topic-id> --endpoint-type storagequeue --endpoint <storage-account-id>/queues/<queue-name>`.
4. Send an event to your topic using `az eventgrid event publish --topic-name <topic-name> --resource-group <resource-group-name> --event-file <event-file-path>`.
5. Check the queue in your storage account to see the event using `az storage queue peek-message --name <queue-name> --account-name <storage-account-name>`.

### Conclusion:
In summary, Azure Event Grid and Azure Event Hub are two powerful services that enable you to build event-driven applications on the cloud. They have different features and capabilities that suit different scenarios and requirements. You should choose the one that best fits your needs and goals.