Node.js - Monitoring the event loop

monitoring.js

import Heavy from 'heavy';

const heavy_instance = new Heavy({
    sampleInterval: 1000,
});
const min_time_between_log_messages = 1000;
const event_loop_logging_threshold = 5;

let logging_interval;

function logIfAboveThreshold({ heavy, logger }) {
    if (!heavy || !heavy.load || !logger) {
        return;
    }
    if (heavy.load.eventLoopDelay > event_loop_logging_threshold) {
        logger.info({
            threshold: event_loop_logging_threshold,
            event_loop_delay: heavy.load.eventLoopDelay,
            heap_used: heavy.load.heapUsed,
            rss: heavy.load.rss,
        }, 'Event loop delay above threshold');
    }
}

export default {
    startLoggingPerformance({ logger }) {
        heavy_instance.start();

        if (logging_interval) {
            clearInterval(logging_interval);
        }

        logging_interval = setInterval(() => {
            logIfAboveThreshold({ heavy: heavy_instance, logger: logger });
        }, min_time_between_log_messages);
    },
};