overleaf/libraries/metrics/event_loop.js

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/*
* decaffeinate suggestions:
* DS102: Remove unnecessary code created because of implicit returns
* DS207: Consider shorter variations of null checks
* Full docs: https://github.com/decaffeinate/decaffeinate/blob/master/docs/suggestions.md
*/
let EventLoopMonitor;
module.exports = (EventLoopMonitor = {
monitor(logger, interval, log_threshold) {
if (interval == null) { interval = 1000; }
if (log_threshold == null) { log_threshold = 100; }
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const Metrics = require("./index");
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// check for logger on startup to avoid exceptions later if undefined
if ((logger == null)) { throw new Error("logger is undefined"); }
// monitor delay in setInterval to detect event loop blocking
let previous = Date.now();
const intervalId = setInterval(function() {
const now = Date.now();
const offset = now - previous - interval;
if (offset > log_threshold) {
logger.warn({offset}, "slow event loop");
}
previous = now;
return Metrics.timing("event-loop-millsec", offset);
}
, interval);
return Metrics.registerDestructor(() => clearInterval(intervalId));
}
});