mongodb-additional-metrics.js

// MongoDB拡張監視スクリプト for Mackerel
const now = Math.floor(new Date().getTime() / 1000)
const c = db.serverStatus().wiredTiger.cache
const lock = db.serverStatus().globalLock

// キャッシュヒット率 (%)
{
  const ratio = (1 - c["pages read into cache"] / c["pages requested from the cache"]) * 100
  print(`mongodb.cache.hit_ratio\t${ratio}\t${now}`)
}

// キャッシュ使用率 (%)
{
  const ratio = c["bytes currently in the cache"] / c["maximum bytes configured"] * 100
  print(`mongodb.cache.usage_ratio\t${ratio}\t${now}`)
}

// dirty page率 (%)
{
  const ratio = c["tracked dirty bytes in the cache"] / c["bytes currently in the cache"] * 100
  print(`mongodb.cache.dirty_ratio\t${ratio}\t${now}`)
}

// ロック待機数
{
  const ratio = lock.currentQueue.readers + lock.currentQueue.writers
  print(`mongodb.lock.queue_total\t${ratio}\t${now}`)
}