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Azure Event Grid client library for JavaScript - version 5.9.0

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Azure Event Grid is a cloud-based service that provides reliable event delivery at massive scale.

Use the client library to:

  • Send events to Event Grid using either the Event Grid, Cloud Events 1.0 schemas, or a custom schema
  • Decode and process events which were delivered to an Event Grid handler
  • Generate Shared Access Signatures for Event Grid topics

Key links:

Getting started

Currently supported environments

See our support policy for more details.

Prerequisites

If you use the Azure CLI, replace <your-resource-group-name> and <your-resource-name> with your own unique names:

Create an Event Grid Topic

az eventgrid topic create --location <location> --resource-group <your-resource-group-name> --name <your-resource-name>

Create an Event Grid Domain

az eventgrid domain create --location <location> --resource-group <your-resource-group-name> --name <your-resource-name>

Install the @azure/eventgrid package

Install the Azure Event Grid client library for JavaScript with npm:

npm install @azure/eventgrid

Create and authenticate a EventGridPublisherClient

To create a client object to access the Event Grid API, you will need the endpoint of your Event Grid topic and a credential. The Event Grid client can use either an Access Key or Shared Access Signature (SAS) created from an access key.

You can find the endpoint for your Event Grid topic either in the Azure Portal or by using the Azure CLI snippet below:

az eventgrid topic show --name <your-resource-name> --resource-group <your-resource-group-name> --query "endpoint"

Using an Access Key

Use the Azure Portal to browse to your Event Grid resource and retrieve an Access Key, or use the Azure CLI snippet below:

az eventgrid topic key list --resource-group <your-resource-group-name> --name <your-event-grid-topic-name>

Once you have an API key and endpoint, you can use the AzureKeyCredential class to authenticate the client as follows:

const { EventGridPublisherClient, AzureKeyCredential } = require("@azure/eventgrid");

const client = new EventGridPublisherClient(
  "<endpoint>",
  "<endpoint schema>",
  new AzureKeyCredential("<Access Key>")
);

Using a SAS Token

Like an access key, a SAS token allows access to sending events to an Event Grid topic. Unlike an access key, which can be used until it is regenerated, a SAS token has an experation time, at which point it is no longer valid. To use a SAS token for authentication, use the AzureSASCredential as follows:

const { EventGridPublisherClient, AzureSASCredential } = require("@azure/eventgrid");

const client = new EventGridPublisherClient(
  "<endpoint>",
  "<endpoint schema>",
  new AzureSASCredential("<SAS Token>")
);

You can generate a SAS token by using the generateSharedAccessSigniture function.

const { generateSharedAccessSignature, AzureKeyCredential } = require("@azure/eventgrid");

// Create a SAS Token which expires on 2020-01-01 at Midnight.
const token = generateSharedAccessSignature(
  "<endpoint>",
  new AzureKeyCredential("<API key>"),
  new Date("2020-01-01T00:00:00")
);

Using Azure Active Directory (AAD)

Azure EventGrid provides integration with Azure Active Directory (Azure AD) for identity-based authentication of requests. With Azure AD, you can use role-based access control (RBAC) to grant access to your Azure Event Grid resources to users, groups, or applications.

To send events to a topic or domain with a TokenCredential, the authenticated identity should have the "EventGrid Data Sender" role assigned.

With the @azure/identity package, you can seamlessly authorize requests in both development and production environments. To learn more about Azure Active Directory, see the @azure/identity README.

For example, use can use DefaultAzureCredential to construct a client which will authenticate using Azure Active Directory:

const { EventGridPublisherClient } = require("@azure/eventgrid");
const { DefaultAzureCredential } = require("@azure/identity");

const client = new EventGridPublisherClient(
  "<endpoint>",
  "<endpoint schema>",
  new DefaultAzureCredential()
);

Key concepts

EventGridPublisherClient

EventGridPublisherClient is used sending events to an Event Grid Topic or an Event Grid Domain.

Event Schemas

Event Grid supports multiple schemas for encoding events. When a Custom Topic or Domain is created, you specify the schema that will be used when publishing events. While you may configure your topic to use a custom schema it is more common to use the already defined Event Grid schema or CloudEvents 1.0 schema. CloudEvents is a Cloud Native Computing Foundation project which produces a specification for describing event data in a common way. When you construct the EventGridPublisherClient you must specify which schema your topic is configured to use:

If your topic is configured to use the Event Grid Schema, set "EventGrid" as the schema type:

const client = new EventGridPublisherClient(
  "<endpoint>",
  "EventGrid",
  new AzureKeyCredential("<API Key>")
);

If your topic is configured to use the Cloud Event Schema, set "CloudEvent" as the schema type:

const client = new EventGridPublisherClient(
  "<endpoint>",
  "CloudEvent",
  new AzureKeyCredential("<API Key>")
);

If your topic is configured to use a Custom Event Schema, set "Custom" as the schema type:

const client = new EventGridPublisherClient(
  "<endpoint>",
  "Custom",
  new AzureKeyCredential("<API Key>")
);

Constructing the client with a different schema than what the topic is configured to expect will result in an error from the service and your events will not be published.

You can see what input schema has been configured for an Event Grid topic by using the Azure CLI snippet below:

az eventgrid topic show --name <your-resource-name> --resource-group <your-resource-group-name> --query "inputSchema"

EventGridDeserializer

Events delivered to consumers by Event Grid are delivered as JSON. Depending on the type of consumer being delivered to, the Event Grid service may deliver one or more events as part of a single payload. While these events may be deserialized using normal JavaScript methods like JSON.parse, this library offers a helper type for deserializing events, called EventGridDeserializer.

Compared with using JSON.parse directly, EventGridDeserializer does some additional conversions while deserializng events:

  1. EventGridDeserializer validates that the required properties of an event are present and are the right types.
  2. EventGridDeserializer converts the event time property into a JavaScript Date object.
  3. When using Cloud Events, binary data may be used for an event's data property (by using Uint8Array). When the event is sent through Event Grid, it is encoded in Base 64. EventGridDeserializer will decode this data back into an instance of Uint8Array.
  4. When deserilizing a System Event (an event generated by another Azure service), EventGridDeserializer will do additional conversions so that the data object matches the corresponding interface which describes its data. When using TypeScript, these interfaces ensure you have strong typing when access properties of the data object for a system event.

When creating an instance of EventGridDeserializer you may supply custom deserializers that are used to further convert the data object.

Distributed Tracing and Cloud Events

This library supports distributed tracing using @azure/core-tracing. When using distributed tracing, this library will create a span during a send operation. In addition, when sending events using the Cloud Events 1.0 schema, the SDK will add distributed tracing metadata to the events using the Distributed Tracing extension. The values for the traceparent and tracestate extension properties correspond to the traceparent and tracestate headers from the HTTP request which sends the events. If an event already has a traceparent extension property it is not updated.

Event Grid on Kubernetes

This library has been tested and validated on Kubernetes using Azure Arc.

Examples

Publish a Custom Event to an Event Grid Topic using the Event Grid Schema

const { EventGridPublisherClient, AzureKeyCredential } = require("@azure/eventgrid");

const client = new EventGridPublisherClient(
  "<endpoint>",
  "EventGrid",
  new AzureKeyCredential("<API key>")
);

await client.send([
  {
    eventType: "Azure.Sdk.SampleEvent",
    subject: "Event Subject",
    dataVersion: "1.0",
    data: {
      hello: "world",
    },
  },
]);

Publish a Custom Event to a Topic in an Event Grid Domain using the Event Grid Schema

Publishing events to an Event Grid Domain is similar to publish to an Event Grid Topic, except that when using the Event Grid schema for events, you must include the topic property. When publishing events in the Cloud Events 1.0 schema, the required source property is used as the name of the topic in the domain to publish to:

const { EventGridPublisherClient, AzureKeyCredential } = require("@azure/eventgrid");

const client = new EventGridPublisherClient(
  "<endpoint>",
  "EventGrid",
  new AzureKeyCredential("<API key>")
);

await client.send([
  {
    topic: "my-sample-topic",
    eventType: "Azure.Sdk.SampleEvent",
    subject: "Event Subject",
    dataVersion: "1.0",
    data: {
      hello: "world",
    },
  },
]);

Deserializing an Event

EventGridDeserializer can be used to deserialize events delivered by Event Grid. In this example we have a cloud event that is deserialized using EventGridDeserializer and use isSystemEvent to detect what type of events they are.

const { EventGridDeserializer, isSystemEvent } = require("@azure/eventgrid");

async function main() {
  const deserializer = new EventGridDeserializer();
  const message = {
    id: "5bc888aa-c2f4-11ea-b3de-0242ac130004",
    source:
      "/subscriptions/<subscriptionid>/resourceGroups/dummy-rg/providers/Microsoft.EventGrid/topics/dummy-topic",
    specversion: "1.0",
    type: "Microsoft.ContainerRegistry.ImagePushed",
    subject: "Test Subject",
    time: "2020-07-10T21:27:12.925Z",
    data: {
      hello: "world",
    },
  };
  const deserializedMessage = await deserializer.deserializeCloudEvents(message);
  console.log(deserializedMessage);

  if (
    deserializedMessage != null &&
    deserializedMessage.length !== 0 &&
    isSystemEvent("Microsoft.ContainerRegistry.ImagePushed", deserializedMessage[0])
  ) {
    console.log("This is a Microsoft.ContainerRegistry.ImagePushed event");
  }
}

main();

Troubleshooting

Logging

Enabling logging may help uncover useful information about failures. In order to see a log of HTTP requests and responses, set the AZURE_LOG_LEVEL environment variable to info. Alternatively, logging can be enabled at runtime by calling setLogLevel in the @azure/logger:

const { setLogLevel } = require("@azure/logger");

setLogLevel("info");

For more detailed instructions on how to enable the logs, you can look at the @azure/logger package docs.

Next steps

Please take a look at the samples directory for detailed examples on how to use this library.

Contributing

If you'd like to contribute to this library, please read the contributing guide to learn more about how to build and test the code.

Impressions