Created
December 22, 2017 15:00
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node.js event loop delay monitor (measures max CPU time spent processing ticks)
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| const NS_PER_SEC = 1e9; | |
| const NS_PER_MS = 1e6; | |
| const SAMPLE_INTERVAL = 10; | |
| class ProcessMonitor { | |
| start(interval) { | |
| let prevTime = [NaN, NaN]; | |
| this.maxEventLoopDelay = 0; | |
| if (!interval) { | |
| interval = 5 * 1000; | |
| } | |
| this.samplerInterval = setInterval(() => { | |
| const now = process.hrtime(); | |
| const diff = [now[0] - prevTime[0], now[1] - prevTime[1]]; | |
| if (!isNaN(diff[0])) { | |
| const delay = ((diff[0] * NS_PER_SEC + diff[1]) / NS_PER_MS) - SAMPLE_INTERVAL; | |
| if (delay > this.maxEventLoopDelay) { | |
| this.maxEventLoopDelay = delay; | |
| } | |
| } | |
| prevTime = now; | |
| }, SAMPLE_INTERVAL); | |
| this.monitorInterval = setInterval(() => { | |
| // Feel free to add this to your stats backend | |
| console.log(this.maxEventLoopDelay + " ms"); | |
| this.maxEventLoopDelay = 0; | |
| }, interval); | |
| } | |
| stop() { | |
| clearTimeout(this.samplerInterval); | |
| clearTimeout(this.monitorInterval); | |
| } | |
| } | |
| module.exports = ProcessMonitor; | |
| /* | |
| This is fast, simple and no external dependencies | |
| Usage: | |
| const monitor = new ProcessMonitor(); | |
| monitor.start(); | |
| Outputs: | |
| [2017-12-22 14:52:52] [LOG] [pid:10396] 16.39679 ms | |
| [2017-12-22 14:52:57] [LOG] [pid:10396] 47.719075 ms | |
| [2017-12-22 14:53:03] [LOG] [pid:10396] 1062.336003 ms <--- I simulate CPU load here | |
| [2017-12-22 14:53:08] [LOG] [pid:10396] 823.406753 ms | |
| [2017-12-22 14:53:13] [LOG] [pid:10396] 10.119005999999999 ms | |
| */ |
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Inspired by https://www.npmjs.com/package/heavy
and https://www.npmjs.com/package/event-loop-monitor