What is sqs-consumer?
The sqs-consumer npm package is a simple to use library for building Amazon Simple Queue Service (SQS) based applications. It allows you to create consumers that process messages from SQS queues with ease, handling message polling, error handling, and visibility timeout extensions.
What are sqs-consumer's main functionalities?
Creating a Consumer
This code sample demonstrates how to create a basic consumer that reads messages from an SQS queue and logs the message body to the console.
const { Consumer } = require('sqs-consumer');
const AWS = require('aws-sdk');
const app = Consumer.create({
queueUrl: 'https://sqs.us-east-1.amazonaws.com/account-id/queue-name',
handleMessage: async (message) => {
console.log(message.Body);
},
sqs: new AWS.SQS()
});
app.on('error', (err) => {
console.error(err.message);
});
app.start();
Error Handling
This code sample shows how to handle errors that occur during message processing. The 'error' event is emitted for general errors, while the 'processing_error' event is specifically for errors that occur during message handling.
const { Consumer } = require('sqs-consumer');
const AWS = require('aws-sdk');
const app = Consumer.create({
queueUrl: 'https://sqs.us-east-1.amazonaws.com/account-id/queue-name',
handleMessage: async (message) => {
throw new Error('Processing error');
},
sqs: new AWS.SQS()
});
app.on('error', (err) => {
console.error('Error occurred:', err.message);
});
app.on('processing_error', (err) => {
console.error('Processing error:', err.message);
});
app.start();
Batch Processing
This code sample demonstrates how to process messages in batches. The 'handleMessageBatch' function receives an array of messages, allowing for more efficient processing.
const { Consumer } = require('sqs-consumer');
const AWS = require('aws-sdk');
const app = Consumer.create({
queueUrl: 'https://sqs.us-east-1.amazonaws.com/account-id/queue-name',
handleMessageBatch: async (messages) => {
messages.forEach(message => console.log(message.Body));
},
sqs: new AWS.SQS()
});
app.on('error', (err) => {
console.error(err.message);
});
app.start();
Other packages similar to sqs-consumer
aws-sdk
The aws-sdk package is the official AWS SDK for JavaScript, which includes support for SQS. It provides a more comprehensive set of tools for interacting with AWS services, including SQS. However, it requires more boilerplate code to achieve the same functionality as sqs-consumer.
sqs-producer
The sqs-producer package is designed for sending messages to SQS queues, complementing the sqs-consumer package. While sqs-consumer focuses on consuming messages, sqs-producer is used for producing messages, making them a good pair for full SQS queue management.
node-sqs
The node-sqs package is another library for interacting with SQS. It provides both producing and consuming capabilities but is less specialized and streamlined compared to sqs-consumer, which is focused solely on consuming messages.
sqs-consumer
Build SQS-based applications without the boilerplate. Just define a function that receives an SQS message and call a callback when the message has been processed.
Installation
npm install sqs-consumer
Usage
var Consumer = require('sqs-consumer');
var app = Consumer.create({
queueUrl: 'https://sqs.eu-west-1.amazonaws.com/account-id/queue-name',
handleMessage: function (message, done) {
done();
}
});
app.on('error', function (err) {
console.log(err.message);
});
app.start();
- The queue is polled continuously for messages using long polling.
- Messages are deleted from the queue once
done()
is called. - Calling
done(err)
with an error object 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. - 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 below.
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 AWS SQS client:
var Consumer = require('sqs-consumer');
var AWS = require('aws-sdk');
AWS.config.update({
region: 'eu-west-1',
accessKeyId: '...',
secretAccessKey: '...'
});
var app = Consumer.create({
queueUrl: 'https://sqs.eu-west-1.amazonaws.com/account-id/queue-name',
handleMessage: function (message, done) {
done();
},
sqs: new AWS.SQS()
});
app.on('error', function (err) {
console.log(err.message);
});
app.start();
API
Consumer.create(options)
Creates a new SQS consumer.
Options
queueUrl
- String - The SQS queue URLregion
- String - The AWS region (default eu-west-1
)handleMessage
- Function - A function to be called whenever a message is received. Receives an SQS message object as its first argument and a function to call when the message has been handled as its second argument (i.e. handleMessage(message, done)
).attributeNames
- Array - List of queue attributes to retrieve (i.e. ['All', 'ApproximateFirstReceiveTimestamp', 'ApproximateReceiveCount']
).messageAttributeNames
- Array - List of message attributes to retrieve (i.e. ['name', 'address']
).batchSize
- Number - The number of messages to request from SQS when polling (default 1
). This cannot be higher than the AWS limit of 10.visibilityTimeout
- Number - The duration (in seconds) that the received messages are hidden from subsequent retrieve requests after being retrieved by a ReceiveMessage request.waitTimeSeconds
- Number - The duration (in seconds) for which the call will wait for a message to arrive in the queue before returning.authenticationErrorTimeout
- Number - The duration (in milliseconds) to wait before retrying after an authentication error (defaults to 10000
).sqs
- Object - An optional AWS SQS object to use if you need to configure the client manually
consumer.start()
Start polling the queue for messages.
consumer.stop()
Stop polling the queue for messages.
Events
Each consumer is an EventEmitter
and emits the following events:
Event | Params | Description |
---|
error | err | Fired when an error occurs interacting with the queue. |
processing_error | err | Fired when an error occurs processing the message. |
message_received | message | Fired when a message is received. |
message_processed | message | Fired when a message is successfully processed and removed from the queue. |
stopped | None | Fired when the consumer finally stops its work. |