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
*/
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module.exports = {
monitor(logger, interval, logThreshold) {
if (interval == null) {
interval = 1000
}
if (logThreshold == null) {
logThreshold = 100
}
const Metrics = require('./index')
// 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 () {
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const now = Date.now()
const offset = now - previous - interval
if (offset > logThreshold) {
logger.warn({ offset }, 'slow event loop')
}
previous = now
return Metrics.timing('event-loop-millsec', offset)
}, interval)
return Metrics.registerDestructor(() => clearInterval(intervalId))
},
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}