NodeJS获取CPU使用率：百分比转换与系统/应用数据区分

问题背景 #

用户现有代码用于获取Node.js应用的CPU使用时长（微秒转换为秒）：

private lastCpuUsage = process.cpuUsage();

getCpuUsage() {
    const cpuUsage = process.cpuUsage();

    const userUsageMicros = cpuUsage.user - this.lastCpuUsage.user;
    const systemUsageMicros = cpuUsage.system - this.lastCpuUsage.system;

    this.lastCpuUsage = cpuUsage;

    console.log({
      cpuUserUsage: userUsageMicros / 1e6, // 转换为秒
      cpuSystemUsage: systemUsageMicros / 1e6,
      cpuTotalUsage: (userUsageMicros + systemUsageMicros) / 1e6
    })
}

示例输出：

{
    "cpuUserUsage": 0.016,
    "cpuSystemUsage": 0.031,
    "cpuTotalUsage": 0.047
}

用户提出两个问题：

1. 如何将cpuUsage转换为百分比单位？
2. 当前输出数据是对应应用本身还是整个主机的？如果仅对应应用，如何获取整机CPU数据？

问题解答 #

1. 转换为百分比单位 #

process.cpuUsage()返回的是当前进程占用CPU的绝对时长，要转成百分比，需要结合两次调用的时间差和主机CPU核心数计算：

• 需记录上次调用的时间戳，计算两次调用的实际流逝时间
• 用「进程CPU占用时长 / 流逝时间」得到单核心占比，再乘以核心数得到总占比（因为进程可以同时利用多核心）

修改后的代码示例：

const os = require('os');
private lastCpuUsage = process.cpuUsage();
private lastTimestamp = Date.now();

getCpuUsage() {
    const cpuUsage = process.cpuUsage();
    const currentTimestamp = Date.now();
    
    // 计算两次调用的时间差（微秒）
    const elapsedMicros = (currentTimestamp - this.lastTimestamp) * 1000;
    // 计算进程CPU使用时长差值
    const userUsageMicros = cpuUsage.user - this.lastCpuUsage.user;
    const systemUsageMicros = cpuUsage.system - this.lastCpuUsage.system;
    const totalUsageMicros = userUsageMicros + systemUsageMicros;
    
    // 获取CPU核心数
    const coreCount = os.cpus().length;
    
    // 转换为百分比
    const cpuUserPercent = (userUsageMicros / elapsedMicros) * coreCount * 100;
    const cpuSystemPercent = (systemUsageMicros / elapsedMicros) * coreCount * 100;
    const cpuTotalPercent = (totalUsageMicros / elapsedMicros) * coreCount * 100;

    this.lastCpuUsage = cpuUsage;
    this.lastTimestamp = currentTimestamp;

    console.log({
      cpuUserPercent: cpuUserPercent.toFixed(2),
      cpuSystemPercent: cpuSystemPercent.toFixed(2),
      cpuTotalPercent: cpuTotalPercent.toFixed(2)
    })
}

2. 数据范围与整机CPU获取 #

• 当前输出的是当前Node.js应用进程自身的CPU使用数据，process.cpuUsage()仅统计当前进程的CPU占用情况。
• 要获取整机CPU使用率，需用os模块的os.cpus()接口，该接口返回每个CPU核心的时间统计（包括空闲、用户态、系统态等时长）。通过记录两次统计的差值，计算整机非空闲时间占总时间的比例得到百分比：

示例代码：

const os = require('os');
private lastCpuTimes = this.getTotalCpuTimes();

// 辅助函数：计算所有核心的总CPU时间
getTotalCpuTimes() {
    const cpus = os.cpus();
    return cpus.reduce((total, cpu) => {
        total.user += cpu.times.user;
        total.system += cpu.times.sys;
        total.idle += cpu.times.idle;
        total.total += cpu.times.user + cpu.times.sys + cpu.times.idle + cpu.times.nice + cpu.times.irq;
        return total;
    }, { user: 0, system: 0, idle: 0, total: 0 });
}

getHostCpuUsage() {
    const currentCpuTimes = this.getTotalCpuTimes();
    // 计算时间差值
    const userDiff = currentCpuTimes.user - this.lastCpuTimes.user;
    const systemDiff = currentCpuTimes.system - this.lastCpuTimes.system;
    const idleDiff = currentCpuTimes.idle - this.lastCpuTimes.idle;
    const totalDiff = currentCpuTimes.total - this.lastCpuTimes.total;
    
    // 计算百分比
    const cpuUserPercent = (userDiff / totalDiff) * 100;
    const cpuSystemPercent = (systemDiff / totalDiff) * 100;
    const cpuIdlePercent = (idleDiff / totalDiff) * 100;
    const cpuTotalPercent = 100 - cpuIdlePercent;

    this.lastCpuTimes = currentCpuTimes;

    console.log({
      hostCpuUserPercent: cpuUserPercent.toFixed(2),
      hostCpuSystemPercent: cpuSystemPercent.toFixed(2),
      hostCpuIdlePercent: cpuIdlePercent.toFixed(2),
      hostCpuTotalPercent: cpuTotalPercent.toFixed(2)
    })
}

内容的提问来源于stack exchange，提问作者great programmer