opentelemetry-node-metrics/metrics/processMaxFileDescriptors.js

An adoption of the node process metrics of prom-client

'use strict'
const fs = require('fs')
const PROCESS_MAX_FDS = 'process_max_fds'
let maxFds

module.exports = (meter, {prefix, labels}) => {
  if (maxFds === undefined) {
    // This will fail if a linux-like procfs is not available.
    try {
      const limits = fs.readFileSync('/proc/self/limits', 'utf8')
      const lines = limits.split('\n')
      for (const line of lines) {
        if (line.startsWith('Max open files')) {
          const parts = line.split(/  +/)
          maxFds = Number(parts[1])
          break
        }
      }
    } catch {
      return
    }
  }

  if (maxFds === undefined) return

  meter.createUpDownCounter(prefix + PROCESS_MAX_FDS, {
    description: 'Maximum number of open file descriptors.'
  }).add(maxFds, labels)
}

module.exports.metricNames = [PROCESS_MAX_FDS]