Qball

What is Qball?

Qball is a library which simplifies processing AWS SQS queues. Normally you need to obtain queue urls, read from a queue, handle the messages, and delete the messages from the queue after you have processed the message successfully. Instead, at a high level, with Qball all you need to do is initialize it and tell it what function you want to process your queue messages.

Installation

• You will need to install the qball library npm install qball --save
• You will also need to install the aws-sdk-library npm install aws-sdk --save

Usage

Example

The following is a basic example configuration to get up and running. It will read messages from the queue "my-queue-name" which is owned by AWS account "123456789" 5 messages at a time every 10 seconds. For each message, it will log out to the console and then delete the message from the queue.

let AWS = require('aws-sdk'); // Include aws-sdk in your module
const qball = require('qball'); // Include qball in your module
const accessKeyId = process.env.AWS_ACCESS_KEY_ID;
const secretAccessKey = process.env.AWS_SECRET_KEY;
const region = 'us-east-1';
const AWS_ACCOUNT_ID = '123456789';
const numMessagesToRead = 5;
const pollingInterval = 10000;
AWS.config.update({ accessKeyId, secretAccessKey, region });

let qb = init(AWS, AWS_ACCOUNT_ID, 'my-queue-name', numMessagesToRead, pollingInterval); // Initialize qball

function handler (msg) { console.log(msg); return msg; } // Define a handler that will process each message read from the queue

qb.start(handler); // Start polling

In the above example, the message gets removed from the queue because the message is returned from the handler function. There is an second argument passed to the handler as well, a function, which you can invoke to indicate that you are done processing the message and wish it to be deleted. An example of this would be:

function handler (message, delMsg) {
  console.log(message);
  delMsg();
}

This library is also Promise friendly, so if you handler is a Promise chain you can return the message at the end of the chain, or invoke the delete message argument all the same.

API Reference

init

The only function exported by the Qball module.

Syntax

init(AWS, accountId, queueName, maxMessages, interval)

Parameters

AWS (object) an instance of the aws-sdk library

accountId (string) the value of the target queue's AWS account ID

queueName (string) the name of the target queue

maxMessages (integer) (defaults to 10) the number of messages to be read from the queue at once from 1 - 10

interval (integer) (defaults to 3000) how often the queue should be polled in milliseconds

Return Value

An API object with start and stop methods

start

Method of the API object returned by the init start and stop functions. Begins polling the configured queue.

Syntax

init(...).start(handler)

Parameters

handler (function) processes queue messages. Accepts two arguments: message and (optional) deleteMessage function

Return Value

A Promise, the value of the argument passed to the next .then() function is an API object with start and stop methods

stop

Method of the API object returned by the init start and stop functions. Stops polling the configured queue.

Syntax

init(...).stop()

Parameters

none

Return Value

A Promise, the value of the argument passed to the next .then() function is an API object with start and stop methods