title

Get started with Azure Service Bus topics (JavaScript)

description

This tutorial shows you how to send messages to Azure Service Bus topics and receive messages from topics' subscriptions using the JavaScript programming language.

author

spelluru

ms.author

spelluru

ms.date

12/08/2023

ms.topic

quickstart

ms.devlang

javascript

ms.custom

devx-track-js

mode-api

sfi-ropc-nochange

Send messages to an Azure Service Bus topic and receive messages from subscriptions to the topic (JavaScript)

[!div class="op_single_selector" title1="Select the programming language:"]

C#

Java

JavaScript

Python

In this tutorial, you complete the following steps:

Create a Service Bus namespace, using the Azure portal.
Create a Service Bus topic, using the Azure portal.
Create a Service Bus subscription to that topic, using the Azure portal.
Write a JavaScript application to use the @azure/service-bus package to:
- Send a set of messages to the topic.
- Receive those messages from the subscription.

Note

This quick start provides step-by-step instructions for a simple scenario of sending a batch of messages to a Service Bus topic and receiving those messages from a subscription of the topic. You can find pre-built JavaScript and TypeScript samples for Azure Service Bus in the Azure SDK for JavaScript repository on GitHub.

Prerequisites

An Azure subscription. To complete this tutorial, you need an Azure account. You can activate your MSDN subscriber benefits or sign up for a free account.
Node.js LTS
Follow steps in the Quickstart: Use the Azure portal to create a Service Bus topic and subscriptions to the topic. You will use only one subscription for this quickstart.

Passwordless

To use this quickstart with your own Azure account, you need:

Install Azure CLI, which provides the passwordless authentication to your developer machine.
Sign in with your Azure account at the terminal or command prompt with az login.
Use the same account when you add the appropriate role to your resource.
Run the code in the same terminal or command prompt.
Note down your topic name and subscription for your Service Bus namespace. You'll need that in the code.

Connection string

Note down the following, which you'll use in the code below:

Service Bus namespace connection string
Service Bus namespace topic name you created
Service Bus namespace subscription

Note

This tutorial works with samples that you can copy and run using Nodejs. For instructions on how to create a Node.js application, see Create and deploy a Node.js application to an Azure Website, or Node.js Cloud Service using Windows PowerShell.

[!INCLUDE service-bus-create-namespace-portal]

[!INCLUDE service-bus-create-topic-subscription-portal]

[!INCLUDE service-bus-passwordless-template-tabbed]

Use Node Package Manager (NPM) to install the package

Passwordless

To install the required npm package(s) for Service Bus, open a command prompt that has npm in its path, change the directory to the folder where you want to have your samples and then run this command.

Install the following packages:

npm install @azure/service-bus @azure/identity

Connection string

To install the required npm package(s) for Service Bus, open a command prompt that has npm in its path, change the directory to the folder where you want to have your samples and then run this command.
Install the following package:
```
npm install @azure/service-bus
```

Send messages to a topic

The following sample code shows you how to send a batch of messages to a Service Bus topic. See code comments for details.

Passwordless

You must have signed in with the Azure CLI's az login in order for your local machine to provide the passwordless authentication required in this code.

Open your favorite editor, such as Visual Studio Code

Create a file called sendtotopic.js and paste the below code into it. This code will send a message to your topic.

[!IMPORTANT] The passwordless credential is provided with the DefaultAzureCredential.

const { ServiceBusClient } = require("@azure/service-bus");
const { DefaultAzureCredential } = require("@azure/identity");

// Replace `<SERVICE-BUS-NAMESPACE>` with your namespace
const fullyQualifiedNamespace = "<SERVICE-BUS-NAMESPACE>.servicebus.windows.net";

// Passwordless credential
const credential = new DefaultAzureCredential();

const topicName = "<TOPIC NAME>";

const messages = [
    { body: "Albert Einstein" },
    { body: "Werner Heisenberg" },
    { body: "Marie Curie" },
    { body: "Steven Hawking" },
    { body: "Isaac Newton" },
    { body: "Niels Bohr" },
    { body: "Michael Faraday" },
    { body: "Galileo Galilei" },
    { body: "Johannes Kepler" },
    { body: "Nikolaus Kopernikus" }
 ];

 async function main() {
    // create a Service Bus client using the passwordless authentication to the Service Bus namespace
    const sbClient = new ServiceBusClient(fullyQualifiedNamespace, credential);

    // createSender() can also be used to create a sender for a queue.
    const sender = sbClient.createSender(topicName);

    try {
        // Tries to send all messages in a single batch.
        // Will fail if the messages cannot fit in a batch.
        // await sender.sendMessages(messages);

        // create a batch object
        let batch = await sender.createMessageBatch();
        for (let i = 0; i < messages.length; i++) {
            // for each message in the array

            // try to add the message to the batch
            if (!batch.tryAddMessage(messages[i])) {
                // if it fails to add the message to the current batch
                // send the current batch as it is full
                await sender.sendMessages(batch);

                // then, create a new batch
                batch = await sender.createMessageBatch();

                // now, add the message failed to be added to the previous batch to this batch
                if (!batch.tryAddMessage(messages[i])) {
                    // if it still can't be added to the batch, the message is probably too big to fit in a batch
                    throw new Error("Message too big to fit in a batch");
                }
            }
        }

        // Send the last created batch of messages to the topic
        await sender.sendMessages(batch);

        console.log(`Sent a batch of messages to the topic: ${topicName}`);

        // Close the sender
        await sender.close();
    } finally {
        await sbClient.close();
    }
}

// call the main function
main().catch((err) => {
    console.log("Error occurred: ", err);
    process.exit(1);
 });

Replace <SERVICE BUS NAMESPACE CONNECTION STRING> with the connection string to your Service Bus namespace.
Replace <TOPIC NAME> with the name of the topic.
Then run the command in a command prompt to execute this file.
```
node sendtotopic.js
```

You should see the following output.

Sent a batch of messages to the topic: mytopic

Connection string

Open your favorite editor, such as Visual Studio Code

Create a file called sendtotopic.js and paste the below code into it. This code will send a message to your topic.

const { ServiceBusClient } = require("@azure/service-bus");

const connectionString = "<SERVICE BUS NAMESPACE CONNECTION STRING>"
const topicName = "<TOPIC NAME>";

const messages = [
    { body: "Albert Einstein" },
    { body: "Werner Heisenberg" },
    { body: "Marie Curie" },
    { body: "Steven Hawking" },
    { body: "Isaac Newton" },
    { body: "Niels Bohr" },
    { body: "Michael Faraday" },
    { body: "Galileo Galilei" },
    { body: "Johannes Kepler" },
    { body: "Nikolaus Kopernikus" }
 ];

 async function main() {
    // create a Service Bus client using the connection string to the Service Bus namespace
    const sbClient = new ServiceBusClient(connectionString);

    // createSender() can also be used to create a sender for a queue.
    const sender = sbClient.createSender(topicName);

    try {
        // Tries to send all messages in a single batch.
        // Will fail if the messages cannot fit in a batch.
        // await sender.sendMessages(messages);

        // create a batch object
        let batch = await sender.createMessageBatch();
        for (let i = 0; i < messages.length; i++) {
            // for each message in the array

            // try to add the message to the batch
            if (!batch.tryAddMessage(messages[i])) {
                // if it fails to add the message to the current batch
                // send the current batch as it is full
                await sender.sendMessages(batch);

                // then, create a new batch
                batch = await sender.createMessageBatch();

                // now, add the message failed to be added to the previous batch to this batch
                if (!batch.tryAddMessage(messages[i])) {
                    // if it still can't be added to the batch, the message is probably too big to fit in a batch
                    throw new Error("Message too big to fit in a batch");
                }
            }
        }

        // Send the last created batch of messages to the topic
        await sender.sendMessages(batch);

        console.log(`Sent a batch of messages to the topic: ${topicName}`);

        // Close the sender
        await sender.close();
    } finally {
        await sbClient.close();
    }
}

// call the main function
main().catch((err) => {
    console.log("Error occurred: ", err);
    process.exit(1);
 });

Replace <SERVICE BUS NAMESPACE CONNECTION STRING> with the connection string to your Service Bus namespace.
Replace <TOPIC NAME> with the name of the topic.
Then run the command in a command prompt to execute this file.
```
node sendtotopic.js
```

You should see the following output.

Sent a batch of messages to the topic: mytopic

Receive messages from a subscription

Passwordless

You must have signed in with the Azure CLI's az login in order for your local machine to provide the passwordless authentication required in this code.

Open your favorite editor, such as Visual Studio Code

Create a file called receivefromsubscription.js and paste the following code into it. See code comments for details.

const { delay, ServiceBusClient, ServiceBusMessage } = require("@azure/service-bus");
const { DefaultAzureCredential } = require("@azure/identity");

// Replace `<SERVICE-BUS-NAMESPACE>` with your namespace
const fullyQualifiedNamespace = "<SERVICE-BUS-NAMESPACE>.servicebus.windows.net";

// Passwordless credential
const credential = new DefaultAzureCredential();

const topicName = "<TOPIC NAME>";
const subscriptionName = "<SUBSCRIPTION NAME>";

 async function main() {
    // create a Service Bus client using the passwordless authentication to the Service Bus namespace
    const sbClient = new ServiceBusClient(fullyQualifiedNamespace, credential);

    // createReceiver() can also be used to create a receiver for a queue.
    const receiver = sbClient.createReceiver(topicName, subscriptionName);

    // function to handle messages
    const myMessageHandler = async (messageReceived) => {
        console.log(`Received message: ${messageReceived.body}`);
    };

    // function to handle any errors
    const myErrorHandler = async (error) => {
        console.log(error);
    };

    // subscribe and specify the message and error handlers
    receiver.subscribe({
        processMessage: myMessageHandler,
        processError: myErrorHandler
    });

    // Waiting long enough before closing the sender to send messages
    await delay(5000);

    await receiver.close();
    await sbClient.close();
}

// call the main function
main().catch((err) => {
    console.log("Error occurred: ", err);
    process.exit(1);
 });

Replace <SERVICE BUS NAMESPACE CONNECTION STRING> with the connection string to the namespace.
Replace <TOPIC NAME> with the name of the topic.
Replace <SUBSCRIPTION NAME> with the name of the subscription to the topic.
Then run the command in a command prompt to execute this file.
```
node receivefromsubscription.js
```

Connection string

Open your favorite editor, such as Visual Studio Code

Create a file called receivefromsubscription.js and paste the following code into it. See code comments for details.

const { delay, ServiceBusClient, ServiceBusMessage } = require("@azure/service-bus");

const connectionString = "<SERVICE BUS NAMESPACE CONNECTION STRING>"
const topicName = "<TOPIC NAME>";
const subscriptionName = "<SUBSCRIPTION NAME>";

 async function main() {
    // create a Service Bus client using the connection string to the Service Bus namespace
    const sbClient = new ServiceBusClient(connectionString);

    // createReceiver() can also be used to create a receiver for a queue.
    const receiver = sbClient.createReceiver(topicName, subscriptionName);

    // function to handle messages
    const myMessageHandler = async (messageReceived) => {
        console.log(`Received message: ${messageReceived.body}`);
    };

    // function to handle any errors
    const myErrorHandler = async (error) => {
        console.log(error);
    };

    // subscribe and specify the message and error handlers
    receiver.subscribe({
        processMessage: myMessageHandler,
        processError: myErrorHandler
    });

    // Waiting long enough before closing the sender to send messages
    await delay(5000);

    await receiver.close();
    await sbClient.close();
}

// call the main function
main().catch((err) => {
    console.log("Error occurred: ", err);
    process.exit(1);
 });

Replace <SERVICE BUS NAMESPACE CONNECTION STRING> with the connection string to the namespace.
Replace <TOPIC NAME> with the name of the topic.
Replace <SUBSCRIPTION NAME> with the name of the subscription to the topic.
Then run the command in a command prompt to execute this file.
```
node receivefromsubscription.js
```

You should see the following output.

Received message: Albert Einstein
Received message: Werner Heisenberg
Received message: Marie Curie
Received message: Steven Hawking
Received message: Isaac Newton
Received message: Niels Bohr
Received message: Michael Faraday
Received message: Galileo Galilei
Received message: Johannes Kepler
Received message: Nikolaus Kopernikus

In the Azure portal, navigate to your Service Bus namespace, switch to Topics in the bottom pane, and select your topic to see the Service Bus Topic page for your topic. On this page, you should see 10 incoming and 10 outgoing messages in the Messages chart.

:::image type="content" source="./media/service-bus-nodejs-how-to-use-topics-subscriptions/topic-page-portal.png" alt-text="Incoming and outgoing messages":::

If you run only the send app next time, on the Service Bus Topic page, you see 20 incoming messages (10 new) but 10 outgoing messages.

:::image type="content" source="./media/service-bus-nodejs-how-to-use-topics-subscriptions/updated-topic-page.png" alt-text="Updated topic page":::

On this page, if you select a subscription in the bottom pane, you get to the Service Bus Subscription page. You can see the active message count, dead-letter message count, and more on this page. In this example, there are 10 active messages that haven't been received by a receiver yet.

:::image type="content" source="./media/service-bus-nodejs-how-to-use-topics-subscriptions/active-message-count.png" alt-text="Active message count":::

Troubleshooting

If you receive an error when running the passwordless version of the JavaScript code about required claims, make sure you are signed in via the Azure CLI command, az login and the appropriate role is applied to your Azure user account.

Clean up resources

Navigate to your Service Bus namespace in the Azure portal, and select Delete on the Azure portal to delete the namespace and the queue in it.

Next steps

See the following documentation and samples:

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Send messages to an Azure Service Bus topic and receive messages from subscriptions to the topic (JavaScript)

Prerequisites

Passwordless

Connection string

Use Node Package Manager (NPM) to install the package

Passwordless

Connection string

Send messages to a topic

Passwordless

Connection string

Receive messages from a subscription

Passwordless

Connection string

Troubleshooting

Clean up resources

Next steps

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Send messages to an Azure Service Bus topic and receive messages from subscriptions to the topic (JavaScript)

Prerequisites

Use Node Package Manager (NPM) to install the package

Send messages to a topic

Receive messages from a subscription

Troubleshooting

Clean up resources

Next steps