TiDB - PD Region Merge 食草兽

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{
  "count": 168,   // 集群中 Region 总数量
  "regions": [
    {
      "id": 241,  // Region id
      "start_key": "7480000000000000FF565F728000000000FF03F07A0000000000FA",
      "end_key": "7480000000000000FF565F728000000000FF0B07BE0000000000FA",
      "epoch": {
        "conf_ver": 5,
        "version": 46
      },
      "peers": [  // Region 成员信息
        {
          "id": 242,
          "store_id": 1
        },
        {
          "id": 243,
          "store_id": 4
        },
        {
          "id": 244,
          "store_id": 5
        }
      ],
      "leader": {
        "id": 244,  // Reigon 成员中 leader id「角色」
        "store_id": 5
      },
      "written_bytes": 0,
      "read_bytes": 0,
      "written_keys": 0,
      "read_keys": 0,
      "approximate_size": 99,     // Region 大小
      "approximate_keys": 478217  // Region Key-Values 数量
    },
  ... ... 省略其他信息

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// EmptyRegionApproximateSize is the region approximate size of an empty region
// (heartbeat size <= 1MB).
const EmptyRegionApproximateSize = 1

...-跳过部分信息-...

// 判断 region approximate size 小于等于 1mb ，定义为 empty-region
if region.GetApproximateSize() <= core.EmptyRegionApproximateSize {
    r.stats[EmptyRegion][regionID] = region
    peerTypeIndex |= EmptyRegion
  }

...-跳过部分信息-...

// 定义 pd_checker_event_count 监控
var (
  checkerCounter = prometheus.NewCounterVec(
    prometheus.CounterOpts{
      Namespace: "pd",
      Subsystem: "checker",
      Name:      "event_count",
      Help:      "Counter of checker events.",
    }, []string{"type", "name"})
)

func init() {
  prometheus.MustRegister(checkerCounter)
}

...-跳过部分信息-...

// 详情见 server/schedule/checker/merge_checker.go
// 调用 mergecheck function ，监控系统记录 +1 调用
// 通过 prometheus count 方式统计该信息
checkerCounter.WithLabelValues("merge_checker", "check").Inc()


...-跳过部分信息-...

// Region Merge 还需要检测其他累计十几项内容
// 可在 server/schedule/checker/merge_checker.go 查看

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// max-merge-region-size 单位 MB；
// 监控上参考“ tikv 总存储量「未压缩」/ tikv 总 region peer 数量”；得到平均 peer 大小
// prometheus 查看 sum(pd_scheduler_store_status{ type="region_size"}) / sum(pd_scheduler_store_status{ type="region_count"}) ；得到单位为 MB
>> pd-ctl config set max-merge-region-size 20

// max-merge-region-keys 单位 KV 数量；监控获取获取不到
>> pd-ctl config set max-merge-region-keys 200000

>> pd-ctl config set merge-schedule-limit 8

1

./pd-ctl --pd 'http://10.0.0.1:2379' -d region | jq ".regions | map(select(.approximate_size < 20 and .approximate_keys < 200000)) | length"