Publish and subscribe with the JavaScript SDK on Dapr Docs

Publish events with the JavaScript SDK

Mon, 01 Jan 0001 00:00:00 +0000

Use DaprClient.pubsub to publish events over HTTP or gRPC with @dapr/dapr 3.19.0 or later. Complete the pub/sub prerequisites before following this guide.

Configure a publisher

The examples use this HTTP client, component pubsub, and topic orders:

import { CommunicationProtocolEnum, DaprClient } from "@dapr/dapr";

const client = new DaprClient({
 daprHost: "127.0.0.1",
 daprPort: "3500",
 communicationProtocol: CommunicationProtocolEnum.HTTP,
});

For gRPC, select CommunicationProtocolEnum.GRPC and port "50001". Run statements containing await in an async function or an ES module. Reuse the client and stop it during application shutdown; see configuration and usage.

Receive events with a JavaScript application server

Mon, 01 Jan 0001 00:00:00 +0000

Use DaprServer.pubsub to receive events through HTTP or gRPC callbacks with @dapr/dapr 3.19.0 or later. Complete the pub/sub prerequisites before following this guide. For workers without an application callback listener, use streaming subscriptions instead.

Register subscriptions before startup

Save the following as subscriber.js in an ES module application:

import { CommunicationProtocolEnum, DaprPubSubStatusEnum, DaprServer } from "@dapr/dapr";

const server = new DaprServer({
 serverHost: "127.0.0.1",
 serverPort: "50002",
 communicationProtocol: CommunicationProtocolEnum.HTTP,
 clientOptions: { daprHost: "127.0.0.1", daprPort: "3500" },
});

await server.pubsub.subscribe("pubsub", "orders", async (data, headers) => {
 console.log("Order received:", data, headers);
 return DaprPubSubStatusEnum.SUCCESS;
});

await server.start();

Run the subscriber with an application port matching serverPort:

Receive events with JavaScript streaming subscriptions

Mon, 01 Jan 0001 00:00:00 +0000

Use DaprClient.pubsub.subscribeStream() to open a bidirectional gRPC stream from your application to the sidecar with @dapr/dapr 3.19.0 or later. It does not require DaprServer, an application callback port, or subscription discovery.

Complete the pub/sub prerequisites first. Streaming uses SubscribeTopicEventsAlpha1, an alpha gRPC API; your Dapr runtime must implement it. HTTP clients reject this operation with HTTPNotSupportedError. Streaming subscriptions do not support routing rules or bulk subscription options.

Run a streaming worker

Save the following as worker.js in an ES module application. The worker runs until SIGINT or SIGTERM, or until the stream fails:

JavaScript pub/sub configuration and usage

Mon, 01 Jan 0001 00:00:00 +0000

This guide covers shared configuration and operational guidance for pub/sub with @dapr/dapr 3.19.0 or later. See the overview to choose between server callbacks and streaming subscriptions.

Client lifetime

Reuse a long-lived DaprClient rather than creating one per message. Await outstanding operations before calling await client.stop() at shutdown.

For server subscriptions, stop the application listener with await server.stop(). For streaming subscriptions, close each subscription and await its closed promise before stopping the client; client.stop() does not close streams. See streaming lifecycle guidance.