# Cluster Alert Rules

__*zz-BGL*__

+ Alert rules are divided into three categories:
  + **`Emergency`**: The highest severity level at which the service is unavailable, manual interventions is required immediately
  + **`Critical`**: Decreased service availability, a close watch on the abnormal metrics is required
  + **`Warning`**: A reminder for an issue or error, no immediate attention is required
+ Following components provide pre-configured alert rules:
  + `TiDB`, `TiKV`, `PD`, `TiFlash`, `TiDB Binlog`, `TiCDC`, `Node_exporter` and `Blackbox_exporter`
+ Each alert rule has **`Name`**, **`Rule`**, **`Description`** and **`Solution`** attributes:
  + Detailed reference - `https://docs.pingcap.com/tidb/stable/alert-rules`

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`Node_exporter` takes care of metrics from the node level.

`Blackbox_exporter` takes care of metrics from the network protocol level.

We will talk about `TiCDC` in other following-up units.

Please refer to the documentation for detail -  `https://docs.pingcap.com/tidb/stable/alert-rules`.