bbc/sqs-consumer

sqs-consumer

Build SQS-based applications without the boilerplate. Just define an async function that handles the SQS message processing.

Installation

To install this package, simply enter the following command into your terminal (or the variant of whatever package manager you are using):

npm install sqs-consumer

If you would like to use JSR instead, you can find the package here.

Node version

We will only support Node versions that are actively or security supported by the Node team. You can find the list of versions that are actively supported here.

Documentation

Visit https://bbc.github.io/sqs-consumer/ for the full API documentation.

Usage

import { Consumer } from "sqs-consumer";

const app = Consumer.create({
  queueUrl: "https://sqs.eu-west-1.amazonaws.com/account-id/queue-name",
  handleMessage: async (message) => {
    // do some work with `message`
  },
});

app.on("error", (err) => {
  console.error(err.message);
});

app.on("processing_error", (err) => {
  console.error(err.message);
});

app.start();

• Polling Behavior: The queue is polled continuously for messages using long polling.
• Message Processing Behavior: By default messages are processed one at a time – a new message won't be received until the first one has been processed. To process messages in parallel, use the batchSize option detailed here.
  • It's also important to await any processing that you are doing to ensure that messages are processed one at a time.
• Message Acknowledgment Behavior:
  • When alwaysAcknowledge is false (the default)
    • Returning undefined, an empty object {}, or an empty array []: Message(s) will NOT be deleted (left on queue for retry)
      • For batch processing, return undefined or [] to prevent acknowledgment of all messages.
      • For single message handling, return undefined or {} to prevent acknowledgment.
    • Returning the message object (or an array of messages in batch processing): Message(s) will be acknowledged and deleted
      • Important: Only the message id(s) that are returned will be deleted.
    • Returning void is discouraged and will be deprecated in a future release.
    • When strictReturn is true: Returning null will throw an error. This will be the default behavior in a future release.
  • When alwaysAcknowledge is true: All messages will be acknowledged and deleted regardless of return value.
• Error Handling: Throwing an error (or returning a rejected promise) from the handler function will cause the message to be left on the queue. An SQS redrive policy can be used to move messages that cannot be processed to a dead letter queue.
• Deletion Process Messages are deleted from the queue once the handler function has completed successfully (the above items should also be taken into account).

FIFO Queue Support

When using SQS Consumer with FIFO (First-In-First-Out) queues, you might see a warning message in your logs.

As mentioned in the warning, we do not explicitly test SQS Consumer with FIFO queues, this means that we cannot guarantee that the library will work as expected, however, with the correct configuration, it should. If you have done that and believe FIFO to be working as expected, you can suppress the warning by setting suppressFifoWarning: true.

To note: In order to maintain FIFO ordering, you should always use the handleMessageBatch method instead of handleMessage.

Credentials

By default the consumer will look for AWS credentials in the places specified by the AWS SDK. The simplest option is to export your credentials as environment variables:

export AWS_SECRET_ACCESS_KEY=...
export AWS_ACCESS_KEY_ID=...

If you need to specify your credentials manually, you can use a pre-configured instance of the SQS Client client.

import { Consumer } from "sqs-consumer";
import { SQSClient } from "@aws-sdk/client-sqs";

const app = Consumer.create({
  queueUrl: "https://sqs.eu-west-1.amazonaws.com/account-id/queue-name",
  handleMessage: async (message) => {
    // ...
  },
  sqs: new SQSClient({
    region: "my-region",
    credentials: {
      accessKeyId: "yourAccessKey",
      secretAccessKey: "yourSecret",
    },
  }),
});

app.on("error", (err) => {
  console.error(err.message);
});

app.on("processing_error", (err) => {
  console.error(err.message);
});

app.on("timeout_error", (err) => {
  console.error(err.message);
});

app.start();

AWS IAM Permissions

Consumer will receive and delete messages from the SQS queue. Ensure sqs:ReceiveMessage, sqs:DeleteMessage, sqs:DeleteMessageBatch, sqs:ChangeMessageVisibility and sqs:ChangeMessageVisibilityBatch access is granted on the queue being consumed.

API

Consumer.create(options)

Creates a new SQS consumer using the defined options.

consumer.start()

Start polling the queue for messages.

consumer.stop(options)

Stop polling the queue for messages. You can find the options definition here.

By default, the value of abort is set to false which means pre existing requests to AWS SQS will still be made until they have concluded. If you would like to abort these requests instead, pass the abort value as true, like so:

consumer.stop({ abort: true })

Graceful shutdowns

Calling consumer.stop() on its own only prevents new polls from being scheduled. The consumer will emit stopped immediately, even if the current long poll or message handler is still running. To wait for the final poll plus any in-flight message processing to finish, set pollingCompleteWaitTimeMs to the maximum amount of time you are willing to wait.

• While waiting, the consumer emits waiting_for_polling_to_complete every second.
• If the timeout elapses first, waiting_for_polling_to_complete_timeout_exceeded fires right before stopped.
• For graceful shutdowns keep abort: false (the default). Passing abort: true cancels the shared AbortController, which halts heartbeat extensions and prevents acknowledgements/deletions from finishing.

Here's an example of a graceful shutdown implementation:

const consumer = Consumer.create({
  queueUrl: "https://sqs.eu-west-1.amazonaws.com/account-id/queue-name",
  handleMessage: async (message) => {
    await doWork(message);
    return message;
  },
  pollingCompleteWaitTimeMs: 10_000, // This will allow up to 10s for the last poll + handler
});

const shutdown = (signal) => {
  console.log(`Received ${signal}, waiting for in-flight work...`);
  consumer.stop();

  consumer.once("waiting_for_polling_to_complete", () => {
    console.log("Still processing in-flight messages...");
  });

  consumer.once("waiting_for_polling_to_complete_timeout_exceeded", () => {
    console.warn("Graceful shutdown timed out, continuing shutdown anyway.");
  });

  consumer.once("stopped", () => {
    console.log("Consumer stopped cleanly");
    process.exit(0);
  });
};

process.once("SIGINT", shutdown);
process.once("SIGTERM", shutdown);

consumer.start();

consumer.status

Returns the current status of the consumer.

• isRunning - true if the consumer has been started and not stopped, false if was not started or if it was stopped.
• isPolling - true if the consumer is actively polling, false if it is not.

Note: This method is not available in versions before v9.0.0 and replaced the method isRunning to supply both running and polling states.

consumer.updateOption(option, value)

Updates the provided option with the provided value.

Please note that any update of the option pollingWaitTimeMs will take effect only on next polling cycle.

You can find out more about this here.

Events

Each consumer is an EventEmitter and emits these events.

Contributing

We welcome and appreciate contributions for anyone who would like to take the time to fix a bug or implement a new feature.

But before you get started, please read the contributing guidelines and code of conduct.

License

SQS Consumer is distributed under the Apache License, Version 2.0, see LICENSE for more information.