Azure Event Grid client library for JavaScript
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
Source code |
Package (NPM) |
API reference documentation |
Product documentation |
Samples
Getting started
Currently supported environments
- Node.js version 8.x.x or higher
- Browser JavaScript
- Apple Safari: latest two versions
- Google Chrome: latest two versions
- Microsoft Edge: all supported versions
- Mozilla FireFox: latest two versions
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");
const token = generateSharedAccessSignature(
"<endpoint>",
new AzureKeyCredential("<API key>"),
new Date("2020-01-01T00:00:00")
);
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:
EventGridDeserializer
validates that the required properties of an event are present and are the right types.EventGridDeserializer
converts the event time property into a JavaScript Date
object.- 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
. - 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.
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. When deserializing an event, you need to know the schema used to deliver the event. In this example we have events being delivered to an Azure Service Bus Queue in the Cloud Events schema. Using the Service Bus SDK we can receive these events from the Service Bus Queue and then deserialize them using EventGridDeserializer
and use isSystemEvent
to detect what type of events they are.
const { ServiceBusClient } = require("@azure/service-bus");
const { DefaultAzureCredential } = require("@azure/identity");
const { EventGridDeserializer, isSystemEvent } = require("@azure/eventgrid");
const client = new ServiceBusClient("<service bus hostname>", new DefaultAzureCredential());
const receiver = client.createReceiver("<queue name>", "peekLock");
const consumer = new EventGridDeserializer();
async function processMessage(message) {
const event = (await consumer.deserializeCloudEvents(message.body))[0];
if (isSystemEvent("Microsoft.ContainerRegistry.ImagePushed", event)) {
console.log(
`${event.time}: Container Registry Image Pushed event for image ${event.data.target.repository}:${event.data.target.tag}`
);
} else if (isSystemEvent("Microsoft.ContainerRegistry.ImageDeleted", event)) {
console.log(
`${event.time}: Container Registry Image Deleted event for repository ${event.data.target.repository}`
);
}
await message.complete();
}
console.log("starting receiver");
receiver.subscribe({
processError: async (err) => {
console.error(err);
},
processMessage
});
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
:
import { setLogLevel } from "@azure/logger";
setLogLevel("info");
For more detailed instructions on how to enable 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.
Related projects