polling_gist6.js

class Poll {
    /**
     * @typedef options
     * @property {number} interval Interval between each poll in `seconds`
     * @property {number} maxPollCount Max number of times to poll
     *
     * @param {options} options
     * @param {(Object) => Promise<boolean>} pollingFunction
     * @param {QueueClientInterface} queueClient
     */
    constructor({ interval, maxPollCount }, pollingFunction, queueClient, logger = console) {
        this.logger = logger;
        this.interval = interval;
        this.queueClient = queueClient;
        this.maxPollCount = maxPollCount;
        this.pollingFunction = pollingFunction;

        // The DLQ pushes all the expired messages to the COLLECTOR_QUEUE
        // and our consumer subscribes to this queue.
        this.mq.listen('COLLECTOR_QUEUE', options);
        this.mq.on('dequeue', (data) => {
            this.fetchAndValidate(data);
        });
    }

    ...
}