Use CloudEvents v1.0 schema with Event Grid

In addition to its default event schema, Azure Event Grid natively supports events in the JSON implementation of CloudEvents v1.0 and HTTP protocol binding. CloudEvents is an open specification for describing event data.

CloudEvents simplifies interoperability by providing a common event schema for publishing and consuming cloud-based events. This schema allows for uniform tooling, standard ways of routing and handling events, and universal ways of deserializing the outer event schema. With a common schema, you can more easily integrate work across platforms.

CloudEvents is being built by several collaborators, including Microsoft, through the Cloud Native Computing Foundation. It's currently available as version 1.0.

This article describes how to use the CloudEvents schema with Event Grid.

CloudEvent schema

Here's an example of an Azure Blob Storage event in CloudEvents format:

{
    "specversion": "1.0",
    "type": "Microsoft.Storage.BlobCreated",  
    "source": "/subscriptions/{subscription-id}/resourceGroups/{resource-group}/providers/Microsoft.Storage/storageAccounts/{storage-account}",
    "id": "9aeb0fdf-c01e-0131-0922-9eb54906e209",
    "time": "2019-11-18T15:13:39.4589254Z",
    "subject": "blobServices/default/containers/{storage-container}/blobs/{new-file}",
    "dataschema": "#",
    "data": {
        "api": "PutBlockList",
        "clientRequestId": "4c5dd7fb-2c48-4a27-bb30-5361b5de920a",
        "requestId": "9aeb0fdf-c01e-0131-0922-9eb549000000",
        "eTag": "0x8D76C39E4407333",
        "contentType": "image/png",
        "contentLength": 30699,
        "blobType": "BlockBlob",
        "url": "https://gridtesting.blob.core.windows.net/testcontainer/{new-file}",
        "sequencer": "000000000000000000000000000099240000000000c41c18",
        "storageDiagnostics": {
            "batchId": "681fe319-3006-00a8-0022-9e7cde000000"
        }
    }
}

For a detailed description of the available fields, their types, and definitions, see CloudEvents v1.0.

The headers values for events delivered in the CloudEvents schema and the Event Grid schema are the same except for content-type. For the CloudEvents schema, that header value is "content-type":"application/cloudevents+json; charset=utf-8". For the Event Grid schema, that header value is "content-type":"application/json; charset=utf-8".

Configure Event Grid for CloudEvents

You can use Event Grid for both input and output of events in the CloudEvents schema. The following table describes the possible transformations:

Event Grid resource Input schema Delivery schema
System topics Event Grid schema Event Grid schema or CloudEvents schema
Custom topics/domains Event Grid schema Event Grid schema or CloudEvents schema
Custom topics/domains CloudEvents schema CloudEvents schema
Custom topics/domains Custom schema Custom schema, Event Grid schema, or CloudEvents schema
Partner topics CloudEvents schema CloudEvents schema

For all event schemas, Event Grid requires validation when you're publishing to an Event Grid topic and when you're creating an event subscription.

For more information, see Event Grid security and authentication.

Input schema

You set the input schema for a custom topic when you create the custom topic.

For the Azure CLI, use:

az eventgrid topic create \
  --name <topic_name> \
  -l westcentralus \
  -g gridResourceGroup \
  --input-schema cloudeventschemav1_0

For PowerShell, use:

New-AzEventGridTopic `
  -ResourceGroupName gridResourceGroup `
  -Location westcentralus `
  -Name <topic_name> `
  -InputSchema CloudEventSchemaV1_0

Output schema

You set the output schema when you create the event subscription.

For the Azure CLI, use:

topicID=$(az eventgrid topic show --name <topic-name> -g gridResourceGroup --query id --output tsv)

az eventgrid event-subscription create \
  --name <event_subscription_name> \
  --source-resource-id $topicID \
  --endpoint <endpoint_URL> \
  --event-delivery-schema cloudeventschemav1_0

For PowerShell, use:

$topicid = (Get-AzEventGridTopic -ResourceGroupName gridResourceGroup -Name <topic-name>).Id

New-AzEventGridSubscription `
  -ResourceId $topicid `
  -EventSubscriptionName <event_subscription_name> `
  -Endpoint <endpoint_URL> `
  -DeliverySchema CloudEventSchemaV1_0

Endpoint validation with CloudEvents v1.0

If you're already familiar with Event Grid, you might be aware of the endpoint validation handshake for preventing abuse. CloudEvents v1.0 implements its own abuse protection semantics by using the HTTP OPTIONS method. To read more about it, see HTTP 1.1 Web Hooks for event delivery - Version 1.0. When you use the CloudEvents schema for output, Event Grid uses the CloudEvents v1.0 abuse protection in place of the Event Grid validation event mechanism.

Use with Azure Functions

Visual Studio or Visual Studio Code

If you're using Visual Studio or Visual Studio Code, and C# programming language to develop functions, make sure that you're using the latest Microsoft.Azure.WebJobs.Extensions.EventGrid NuGet package (version 3.2.1 or above).

In Visual Studio, use the Tools -> NuGet Package Manager -> Package Manager Console, and run the Install-Package command (Install-Package Microsoft.Azure.WebJobs.Extensions.EventGrid -Version 3.2.1). Alternatively, right-click the project in the Solution Explorer window, and select Manage NuGet Packages menu to browse for the NuGet package, and install or update it to the latest version.

In VS Code, update the version number for the Microsoft.Azure.WebJobs.Extensions.EventGrid package in the csproj file for your Azure Functions project.

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <AzureFunctionsVersion>v4</AzureFunctionsVersion>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.EventGrid" Version="3.2.1" />
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="4.1.1" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
</Project>

The following example shows an Azure Functions version 3.x function that's developed in either Visual Studio or Visual Studio Code. It uses a CloudEvent binding parameter and EventGridTrigger.

using Azure.Messaging;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.EventGrid;
using Microsoft.Extensions.Logging;

namespace Company.Function
{
    public static class CloudEventTriggerFunction
    {
        [FunctionName("CloudEventTriggerFunction")]
        public static void Run(
            ILogger logger,
            [EventGridTrigger] CloudEvent e)
        {
            logger.LogInformation("Event received {type} {subject}", e.Type, e.Subject);
        }
    }
}

Azure portal development experience

If you're using the Azure portal to develop an Azure function, follow these steps:

  1. Update the name of the parameter in function.json file to cloudEvent.

    {
      "bindings": [
        {
          "type": "eventGridTrigger",
          "name": "cloudEvent",
          "direction": "in"
        }
      ]
    }    
    
  2. Update the run.csx file as shown in the following sample code.

    #r "Azure.Core"
    
    using Azure.Messaging;
    
    public static void Run(CloudEvent cloudEvent, ILogger logger)
    {
        logger.LogInformation("Event received {type} {subject}", cloudEvent.Type, cloudEvent.Subject);
    }
    

Note

For more information, see Azure Event Grid trigger for Azure Functions.

Next steps