tiflash: add scale.md doc (#2184)

TOC.md

@@ -300,6 +300,7 @@
     - [Deploy a TiFlash Cluster](/reference/tiflash/deploy.md)
     - [Use TiFlash](/reference/tiflash/use-tiflash.md)
     - [Monitor TiFlash](/reference/tiflash/monitor.md)
+    - [Scale TiFlash](/reference/tiflash/scale.md)
     - [Configure TiFlash](/reference/tiflash/configuration.md)
   + TiDB Binlog
     - [Overview](/reference/tidb-binlog/overview.md)

reference/tiflash/scale.md

@@ -0,0 +1,128 @@
+---
+title: Scale the TiFlash Cluster
+summary: Learn how to scale in and out nodes in the TiFlash cluster.
+category: reference
+---
+
+# Scale the TiFlash Cluster
+
+This document describes how to scale in and out nodes in the TiFlash cluster.
+
+## Scale out a TiFlash node
+
+The following example shows how to scale out a TiFlash node if you deploy TiFlash on the `192.168.1.1` node.
+
+1. Edit the `inventory.ini` file to add the TiFlash node information:
+
+    Currently, you can only add IP but not domain name.
+
+    {{< copyable "" >}}
+
+    ```ini
+    [tiflash_servers]
+    192.168.1.1
+    ```
+
+2. Edit the `hosts.ini` file to add the node information:
+
+    {{< copyable "" >}}
+
+    ```ini
+    [servers]
+    192.168.1.1
+    [all:vars]
+    username = tidb
+    ntp_server = pool.ntp.org
+    ```
+
+3. Initialize the new node:
+
+    - Configure the SSH mutual trust and sudo rules on the Control Machine:
+
+        {{< copyable "shell-regular" >}}
+
+        ```shell
+        ansible-playbook -i hosts.ini create_users.yml -l 192.168.1.1 -u root -k
+        ```
+
+    - Install the NTP service on the target machine:
+
+        {{< copyable "shell-regular" >}}
+
+        ```shell
+        ansible-playbook -i hosts.ini deploy_ntp.yml -u tidb -b
+        ```
+
+    - Initialize the node on the target machine:
+
+        {{< copyable "shell-regular" >}}
+
+        ```shell
+        ansible-playbook bootstrap.yml -l 192.168.1.1
+        ```
+
+4. Deploy the new node:
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    ansible-playbook deploy.yml -l 192.168.1.1
+    ```
+
+5. Start the new node:
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    ansible-playbook start.yml -l 192.168.1.1
+    ```
+
+6. Update the configuration of Prometheus and restart it:
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    ansible-playbook rolling_update_monitor.yml --tags=prometheus
+    ```
+
+7. Access the monitoring platform using your browser, and view the status of the cluster and the new node.
+
+## Scale in a TiFlash node
+
+The following example shows how to scale in a TiFlash node if you stop the TiFlash service on the `192.168.1.1` node.
+
+> **Note:**
+>
+> The offline process described in this section does not delete the data on the offline node. If you need to take the node online again, delete the data manually.
+
+1. Take down the node to be scaled in. See [Take a TiFlash node down](/reference/tiflash/maintain.md#take-a-tiflash-node-down) for details.
+
+2. Check whether the node has been offline successfully using Grafana or pd-ctl (the offline process takes some time).
+
+3. After the `store` corresponding to TiFlash disappears, or the `state_name` becomes `Tomestone`, execute the following command to shutdown the TiFlash process:
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    ansible-playbook stop.yml -l 192.168.1.1
+    ```
+
+    If the node still has other services and you want to stop TiFlash only, use the following command:
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    ansible-playbook stop.yml -t tiflash -l 192.168.1.1
+    ```
+
+4. Edit the `inventory.ini` and `hosts.ini` files to remove the node information.
+
+5. Update the configuration of Prometheus and restart it:
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    ansible-playbook rolling_update_monitor.yml --tags=prometheus
+    ```
+
+6. Access the monitoring platform using your browser, and view the status of the cluster.