Nodejs监控事件循环异常示例详解

// 环境准备
const http = require('http');
const path = require('path');
const {execFile, execFileSync} = require('child_process');

const max = 9999;
const getComputedValueFromChildProcess = (max) => execFileSync('node', [path.join(__dirname, './childprocess.js'), max]);

http.createServer((req, res) => {
 const k = getComputedValueFromChildProcess(max);
 res.write('origin-text: ' + k);
 res.end();
}).listen(8888);


// 第一版实现
const MS_MULTI = 1000 * 1000;
const blockDelta = 10 * MS_MULTI;
let start;
function meature() {
 start = process.hrtime();
 setImmediate(function() {
  let seconds;
  [seconds, start] = process.hrtime(start);
  if (seconds * 1000 * MS_MULTI + start > blockDelta) {
   console.log(`node.eventloop_blocked for ${seconds}secs and ${(start / MS_MULTI).toFixed(2)}ms.`);
  }
  meature();
 });
}
meature();

// childprocess.js 文件
#!/use/env node
const args = Number(process.argv[2]);
function computeIo(args) {
 let k;
 for (let i = 0; i < args; ++i) {
  for (let j = 0; j < args; ++j) {
   k = i + j;
  } 
 }
 return k;
}
console.log(computeIo(args));

# 没有请求前
# 等了很久出现一个15ms
➜ test node blocked.js
node.eventloop_blocked for 0secs and 15.71ms.

# 当我执行几次
curl http://localhost:8888
# 出现：
node.eventloop_blocked for 0secs and 175.60ms.
node.eventloop_blocked for 0secs and 149.92ms.
node.eventloop_blocked for 0secs and 147.25ms.

const EVERY_SEC_MIN_LOOPS = 1000000; // 定义每秒最小循环数
let times = 0; // 一次采样中的循环数
let nowShowIncreaseTimes = false; // 当前是否应该增加 times
let start = Date.now();
const CD = 10 * 1000; // 间隔
function meature(callback = () => {}) {
 setTimeout(function() {
  start = Date.now();
  nowShowIncreaseTimes = true;
  _inter();
  setTimeout(() => {
   endMeature();
   meature(); // 开始预约下次采样
  }, 2000);
 }, CD);
}
function _inter() {
 setImmediate(() => {
  if (nowShowIncreaseTimes) {
   ++times;
   return _inter();
  }
 });
}

function endMeature() {
 
 const now = Date.now();
 nowShowIncreaseTimes = false;
 const totalMsSpan = now - start;
 const everySecLoops = (times / (totalMsSpan / 1000)).toFixed(0);
 if (everySecLoops < EVERY_SEC_MIN_LOOPS) {
  console.log(`当前每秒循环数${everySecLoops}`);
 }
 times = 0;
 return everySecLoops
}
meature();

// non-blocked.js
const max = 9999;
const getComputedValueFromChildProcess = (max) => new Promise((res, rej) => {
 execFile('node', [path.join(__dirname, './childprocess.js'), max], (err, stdout) => {
  const valueFromChildProcess = Number(stdout);
  res(valueFromChildProcess);
 });
});

http.createServer(async (req, res) => {
 const k = await getComputedValueFromChildProcess(max);
 res.write('origin-text: ' + k);
 res.end();
}).listen(8888);