automatically record heapdump snapshots in node.js #nodejs #debug #util

recordHeapdump.js

'use strict';
/* eslint-disable no-console */

// NOTE: update the debug scope
const debug = require('debug')('recordHeapdump');
const heapdump = require('heapdump');

var interval;
var nextThreshold_MB = 0;

module.exports = recordHeapdump;

/**
 * Automatically records a heapdump snapshot to the local temp directory
 * for a given memory size threshold.
 * @param {number} threshold_MB Delta between snapshot sizes
 * @param {number} interval_ms How often to check the memory for a snapshot
 */
function recordHeapdump(threshold_MB=100, interval_ms=1000 * 2) {

    if (interval) {
        clearInterval(interval);
    }

    interval = setInterval(function heapdumpInterval() {
        var rss_MB = process.memoryUsage().rss / (1 << 20);

        debug('rss_MB:', rss_MB.toString().padEnd(12), 'nextThreshold_MB:', nextThreshold_MB);

        if (rss_MB > nextThreshold_MB) {
            heapdump.writeSnapshot(`temp/${Date.now()}.heapsnapshot`, (err, filename) => {
                if (err) {
                    console.error('heapsnapshot error', err);
                } else {
                    console.log(`wrote heapsnapshot ${filename}, rss: ${rss_MB} MB`);
                }
            });

            nextThreshold_MB += threshold_MB;
        }
    }, interval_ms);
}