get_cpus_length/index.js

Solve the problem of Not correct os.cpus().length inside the docker container with cpus limited.

const fs = require("fs");
const os = require("os");

function readNumber(file) {
  return Number(fs.readFileSync(file, "utf-8"));
}

// @xiaoxiaojx
// Reference solution for go-lang https://github.com/uber-go/automaxprocs

/**
 * @returns {number}
 */
function getCpuLimits() {
  try {
    return (
      // @xiaoxiaojx
      // 仅针对于使用 CFS 调度策略的实例 https://www.kernel.org/doc/Documentation/scheduler/sched-bwc.txt
      // cfs.cpu_period_us 文件记录了调度周期，单位是 us；默认值一般是 100’000，即 100 ms
      // cfs.cpu_quota_us 记录了每个调度周期进程允许使用 cpu 的量，单位也是 us。值为 -1 表示无限制；对于 4C 的容器，这个值一般是 400’000
      readNumber("/sys/fs/cgroup/cpu/cpu.cfs_quota_us") /
      readNumber("/sys/fs/cgroup/cpu/cpu.cfs_period_us")
    );
  } catch (err) {
    return -1;
  }
}

/**
 * @returns {number}
 */
module.exports = () => {
  const maybeResult = getCpuLimits();

  if (maybeResult > 0) {
    return maybeResult;
  }

  return os.cpus().length;
};

module.exports.getCpuLimits = getCpuLimits;