@april9/sqs-consumer

sqs-consumer

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

Installation

npm install sqs-consumer --save

Usage

const { Consumer, AwsQueueProvider } = require('sqs-consumer');
const provider = new AwsQueueProvider('https://sqs.eu-west-1.amazonaws.com/account-id/queue-name');
const app = Consumer.create(provider, {
  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();

• The queue is polled continuously for messages using long polling.
• Messages are deleted from the queue once the handler function has completed successfully.
• 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.
• 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.
• By default, the default Node.js HTTP/HTTPS SQS agent creates a new TCP connection for every new request (AWS SQS documentation). To avoid the cost of establishing a new connection, you can reuse an existing connection by passing a new SQS instance with keepAlive: true.

const { Consumer, AwsQueueProvider } = require('sqs-consumer');
const AWS = require('aws-sdk');
const sqs = new AWS.SQS({
  httpOptions: {
    agent: new https.Agent({
      keepAlive: true
    })
  }
});

const provider = new AwsQueueProvider('https://sqs.eu-west-1.amazonaws.com/account-id/queue-name', { sqs });
const app = Consumer.create(provider, {
  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();

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:

const { Consumer } = require('sqs-consumer');
const AWS = require('aws-sdk');

AWS.config.update({
  region: 'eu-west-1',
  accessKeyId: '...',
  secretAccessKey: '...'
});

const provider = new AwsQueueProvider('https://sqs.eu-west-1.amazonaws.com/account-id/queue-name', {
  sqs: new AWS.SQS()
});
const app = Consumer.create(provider, {
  handleMessage: async (message) => {
    // ...
  }
});

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();

API

Consumer.create(provider, options)

Creates a new SQS consumer.

Provider

• Choose between AWS or Azure as queue provider by initialising AwsQueueProvider or AzureQueueProvider

Options

• handleMessage - Function - An async function (or function that returns a Promise) to be called whenever a message is received. Receives an SQS message object as it's first argument.
• handleMessageBatch - Function - An async function (or function that returns a Promise) to be called whenever a batch of messages is received. Similar to handleMessage but will receive the list of messages, not each message individually. If both are set, handleMessageBatch overrides handleMessage.
• handleMessageTimeout - Number - Time in ms to wait for handleMessage to process a message before timing out. Emits timeout_error on timeout. By default, if handleMessage times out, the unprocessed message returns to the end of the queue.
• 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.
• heartbeatInterval - Number - The interval (in seconds) between requests to extend the message visibility timeout. On each heartbeat the visibility is extended by adding visibilityTimeout to the number of seconds since the start of the handler function. This value must less than visibilityTimeout.
• terminateVisibilityTimeout - Boolean - If true, sets the message visibility timeout to 0 after a processing_error (defaults to false).
• authenticationErrorTimeout - Number - The duration (in milliseconds) to wait before retrying after an authentication error (defaults to 10000).
• pollingWaitTimeMs - Number - The duration (in milliseconds) to wait before repolling the queue (defaults to 10000).
• sqs - Object - An optional AWS SQS object to use if you need to configure the client manually
• receiveOptions - Object - Extra parameters to be passed in ReceiveMessage. For more information check SQS or StorageQueue documentation.

consumer.start()

Start polling the queue for messages.

consumer.stop()

Stop polling the queue for messages.

consumer.isRunning

Returns the current polling state of the consumer: true if it is actively polling, false if it is not.

Events

Each consumer is an EventEmitter and emits the following events:

Event	Params	Description
error	err, [message]	Fired when an error occurs interacting with the queue. If the error correlates to a message, that error is included in Params
processing_error	err, message	Fired when an error occurs processing the message.
timeout_error	err, message	Fired when handleMessageTimeout is supplied as an option and if handleMessage times out.
message_received	message	Fired when a message is received.
message_processed	message	Fired when a message is successfully processed and removed from the queue.
response_processed	None	Fired after one batch of items (up to batchSize) has been successfully processed.
stopped	None	Fired when the consumer finally stops its work.
empty	None	Fired when the queue is empty (All messages have been consumed).

AWS IAM Permissions

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

Contributing

See contributing guidelines.