sqs-consumer
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Build SQS-based Node applications without the boilerplate
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# sqs-consumer
[](https://npmjs.org/package/sqs-consumer)
[](https://github.com/bbc/sqs-consumer/actions/workflows/test.yml)
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):
```bash
npm install sqs-consumer
```
If you would like to use JSR instead, you can find the package [here](https://jsr.io/@bbc/sqs-consumer).
### 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](https://nodejs.org/en/about/releases/).
## Documentation
Visit [https://bbc.github.io/sqs-consumer/](https://bbc.github.io/sqs-consumer/) for the full API documentation.
## Usage
```js
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](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-long-polling.html).
- **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](https://bbc.github.io/sqs-consumer/interfaces/ConsumerOptions.html#batchSize).
- 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](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/SQSDeadLetterQueue.html) 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](https://docs.aws.amazon.com/AWSJavaScriptSDK/guide/node-configuring.html#Setting_AWS_Credentials). The simplest option is to export your credentials as environment variables:
```bash
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](https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/clients/client-sqs/classes/sqsclient.html) client.
```js
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](https://bbc.github.io/sqs-consumer/interfaces/ConsumerOptions.html).
### `consumer.start()`
Start polling the queue for messages.
### `consumer.stop(options)`
Stop polling the queue for messages. [You can find the options definition here](https://bbc.github.io/sqs-consumer/interfaces/StopOptions.html).
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 })`
### `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](https://bbc.github.io/sqs-consumer/classes/Consumer.html#updateOption).
### Events
Each consumer is an [`EventEmitter`](https://nodejs.org/api/events.html) and [emits these events](https://bbc.github.io/sqs-consumer/interfaces/Events.html).
## 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](https://github.com/bbc/sqs-consumer/blob/main/.github/CONTRIBUTING.md) and [code of conduct](https://github.com/bbc/sqs-consumer/blob/main/.github/CODE_OF_CONDUCT.md).
## License
SQS Consumer is distributed under the Apache License, Version 2.0, see [LICENSE](https://github.com/bbc/sqs-consumer/blob/main/LICENSE) for more information.