Important

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Scale the TiDB Cluster Using TiUP

The capacity of a TiDB cluster can be increased or decreased without interrupting the online services.

This document describes how to scale the TiDB, TiKV, PD, TiCDC, or TiFlash cluster using TiUP. If you have not installed TiUP, refer to the steps in Install TiUP on the control machine and import the cluster into TiUP before you use TiUP to scale the TiDB cluster.

To view the current cluster name list, run tiup cluster list.

For example, if the original topology of the cluster is as follows:

Host IP	Service
10.0.1.3	TiDB + TiFlash
10.0.1.4	TiDB + PD
10.0.1.5	TiKV + Monitor
10.0.1.1	TiKV
10.0.1.2	TiKV

Scale out a TiDB/PD/TiKV cluster

If you want to add a TiDB node to the 10.0.1.5 host, take the following steps.

Note

You can take similar steps to add the PD node. Before you add the TiKV node, it is recommended that you adjust the PD scheduling parameters in advance according to the cluster load.

Configure the scale-out topology:
Note
- The port and directory information is not required by default.
- If multiple instances are deployed on a single machine, you need to allocate different ports and directories for them. If the ports or directories have conflicts, you will receive a notification during deployment or scaling.
- Since TiUP v1.0.0, the scale-out configuration will inherit the global configuration of the original cluster.
Add the scale-out topology configuration in the scale-out.yaml file:
```
vi scale-out.yaml
```
```
tidb_servers:
- host: 10.0.1.5
  ssh_port: 22
  port: 4000
  status_port: 10080
  deploy_dir: /data/deploy/install/deploy/tidb-4000
  log_dir: /data/deploy/install/log/tidb-4000
```
Here is a TiKV configuration file template:
```
tikv_servers:
- host: 10.0.1.5
  ssh_port: 22
  port: 20160
  status_port: 20180
  deploy_dir: /data/deploy/install/deploy/tikv-20160
  data_dir: /data/deploy/install/data/tikv-20160
  log_dir: /data/deploy/install/log/tikv-20160
```
Here is a PD configuration file template:
```
pd_servers:
- host: 10.0.1.5
  ssh_port: 22
  name: pd-1
  client_port: 2379
  peer_port: 2380
  deploy_dir: /data/deploy/install/deploy/pd-2379
  data_dir: /data/deploy/install/data/pd-2379
  log_dir: /data/deploy/install/log/pd-2379
```
To view the configuration of the current cluster, run tiup cluster edit-config <cluster-name>. Because the parameter configuration of global and server_configs is inherited by scale-out.yaml and thus also takes effect in scale-out.yaml.
After the configuration, the current topology of the cluster is as follows:
Host IP Service
10.0.1.3 TiDB + TiFlash
10.0.1.4 TiDB + PD
10.0.1.5 TiDB + TiKV + Monitor
10.0.1.1 TiKV
10.0.1.2 TiKV
Run the scale-out command:
```
tiup cluster scale-out <cluster-name> scale-out.yaml
```
Note
The command above is based on the assumption that the mutual trust has been configured for the user to execute the command and the new machine. If the mutual trust cannot be configured, use the -p option to enter the password of the new machine, or use the -i option to specify the private key file.
If you see the Scaled cluster <cluster-name> out successfully, the scale-out operation is successfully completed.
Check the cluster status:
```
tiup cluster display <cluster-name>
```
Access the monitoring platform at http://10.0.1.5:3000 using your browser to monitor the status of the cluster and the new node.

After the scale-out, the cluster topology is as follows:

Host IP	Service
10.0.1.3	TiDB + TiFlash
10.0.1.4	TiDB + PD
10.0.1.5	TiDB + TiKV + Monitor
10.0.1.1	TiKV
10.0.1.2	TiKV

Scale out a TiFlash cluster

If you want to add a TiFlash node to the 10.0.1.4 host, take the following steps.

Note

When adding a TiFlash node to an existing TiDB cluster, you need to note the following things:

Confirm that the current TiDB version supports using TiFlash. Otherwise, upgrade your TiDB cluster to v4.0 or later versions.
Execute the tiup ctl:<cluster-version> pd -u http://<pd_ip>:<pd_port> config set enable-placement-rules true command to enable the Placement Rules feature. Or execute the corresponding command in pd-ctl.

Add the node information to the scale-out.yaml file:
Create the scale-out.yaml file to add the TiFlash node information.
```
tiflash_servers:
  - host: 10.0.1.4
```
Currently, you can only add IP but not domain name.
Run the scale-out command:
```
tiup cluster scale-out <cluster-name> scale-out.yaml
```
Note
The command above is based on the assumption that the mutual trust has been configured for the user to execute the command and the new machine. If the mutual trust cannot be configured, use the -p option to enter the password of the new machine, or use the -i option to specify the private key file.
View the cluster status:
```
tiup cluster display <cluster-name>
```
Access the monitoring platform at http://10.0.1.5:3000 using your browser, and view the status of the cluster and the new node.

After the scale-out, the cluster topology is as follows:

Host IP	Service
10.0.1.3	TiDB + TiFlash
10.0.1.4	TiDB + PD + TiFlash
10.0.1.5	TiDB+ TiKV + Monitor
10.0.1.1	TiKV
10.0.1.2	TiKV

Scale out a TiCDC cluster

If you want to add two TiCDC nodes to the 10.0.1.3 and 10.0.1.4 hosts, take the following steps.

Add the node information to the scale-out.yaml file:

Create the scale-out.yaml file to add the TiCDC node information.

cdc_servers:
  - host: 10.0.1.3
    gc-ttl: 86400
    data_dir: /data/deploy/install/data/cdc-8300
  - host: 10.0.1.4
    gc-ttl: 86400
    data_dir: /data/deploy/install/data/cdc-8300

Run the scale-out command:
```
tiup cluster scale-out <cluster-name> scale-out.yaml
```
Note
The command above is based on the assumption that the mutual trust has been configured for the user to execute the command and the new machine. If the mutual trust cannot be configured, use the -p option to enter the password of the new machine, or use the -i option to specify the private key file.
View the cluster status:
```
tiup cluster display <cluster-name>
```
Access the monitoring platform at http://10.0.1.5:3000 using your browser, and view the status of the cluster and the new nodes.

After the scale-out, the cluster topology is as follows:

Host IP	Service
10.0.1.3	TiDB + TiFlash + TiCDC
10.0.1.4	TiDB + PD + TiFlash + TiCDC
10.0.1.5	TiDB+ TiKV + Monitor
10.0.1.1	TiKV
10.0.1.2	TiKV

Scale in a TiDB/PD/TiKV cluster

If you want to remove a TiKV node from the 10.0.1.5 host, take the following steps.

Note

You can take similar steps to remove the TiDB and PD node.
Because the TiKV, TiFlash, and TiDB Binlog components are taken offline asynchronously and the stopping process takes a long time, TiUP takes them offline in different methods. For details, see Particular handling of components' offline process.

Note

The PD Client in TiKV caches the list of PD nodes.

In versions earlier than v4.0.3, TiKV does not automatically and regularly update the cache of the PD node list. The cache is updated only after the PD leader switches or TiKV restarts to load the latest configuration. To avoid the issue of an expired list of PD nodes cached by TiKV, the PD cluster should contain at least one PD node that existed before the scaling-in or scaling-out. If this condition is not met, you need to manually perform the PD leader transfer to update the PD cache list in TiKV.
Since v4.0.3, TiKV has a mechanism to automatically and regularly update PD nodes, which can help mitigate the issue of an expired list of PD nodes cached by TiKV. However, after scaling out PD, you should try to avoid directly removing all PD nodes at once that existed before the scaling. If necessary, before making all the previously existing PD nodes offline, make sure to switch the PD leader to a newly added PD node.

View the node ID information:

tiup cluster display <cluster-name>

Starting /root/.tiup/components/cluster/v0.4.6/cluster display <cluster-name>
TiDB Cluster: <cluster-name>
TiDB Version: v4.0.16
ID              Role         Host        Ports                            Status  Data Dir                Deploy Dir
--              ----         ----        -----                            ------  --------                ----------
10.0.1.3:8300   cdc          10.0.1.3    8300                             Up      data/cdc-8300           deploy/cdc-8300
10.0.1.4:8300   cdc          10.0.1.4    8300                             Up      data/cdc-8300           deploy/cdc-8300
10.0.1.4:2379   pd           10.0.1.4    2379/2380                        Healthy data/pd-2379            deploy/pd-2379
10.0.1.1:20160  tikv         10.0.1.1    20160/20180                      Up      data/tikv-20160         deploy/tikv-20160
10.0.1.2:20160  tikv         10.0.1.2    20160/20180                      Up      data/tikv-20160         deploy/tikv-20160
10.0.1.5:20160  tikv         10.0.1.5    20160/20180                      Up      data/tikv-20160         deploy/tikv-20160
10.0.1.3:4000   tidb         10.0.1.3    4000/10080                       Up      -                       deploy/tidb-4000
10.0.1.4:4000   tidb         10.0.1.4    4000/10080                       Up      -                       deploy/tidb-4000
10.0.1.5:4000   tidb         10.0.1.5    4000/10080                       Up      -                       deploy/tidb-4000
10.0.1.3:9000   tiflash      10.0.1.3    9000/8123/3930/20170/20292/8234  Up      data/tiflash-9000       deploy/tiflash-9000
10.0.1.4:9000   tiflash      10.0.1.4    9000/8123/3930/20170/20292/8234  Up      data/tiflash-9000       deploy/tiflash-9000
10.0.1.5:9090   prometheus   10.0.1.5    9090                             Up      data/prometheus-9090    deploy/prometheus-9090
10.0.1.5:3000   grafana      10.0.1.5    3000                             Up      -                       deploy/grafana-3000
10.0.1.5:9093   alertmanager 10.0.1.5    9093/9294                        Up      data/alertmanager-9093  deploy/alertmanager-9093

Run the scale-in command:
```
tiup cluster scale-in <cluster-name> --node 10.0.1.5:20160
```
The --node parameter is the ID of the node to be taken offline.
If you see the Scaled cluster <cluster-name> in successfully, the scale-in operation is successfully completed.
Check the cluster status:
The scale-in process takes some time. If the status of the node to be scaled in becomes Tombstone, that means the scale-in operation is successful.
To check the scale-in status, run the following command:
```
tiup cluster display <cluster-name>
```
Access the monitoring platform at http://10.0.1.5:3000 using your browser, and view the status of the cluster.

The current topology is as follows:

Host IP	Service
10.0.1.3	TiDB + TiFlash + TiCDC
10.0.1.4	TiDB + PD + TiFlash + TiCDC
10.0.1.5	TiDB + Monitor (TiKV is deleted)
10.0.1.1	TiKV
10.0.1.2	TiKV

Scale in a TiFlash cluster

If you want to remove a TiFlash node from the 10.0.1.4 host, take the following steps.

1. Adjust the number of replicas of the tables according to the number of remaining TiFlash nodes

Before the node goes down, make sure that the number of remaining nodes in the TiFlash cluster is no smaller than the maximum number of replicas of all tables. Otherwise, modify the number of TiFlash replicas of the related tables.

For all tables whose replicas are greater than the number of remaining TiFlash nodes in the cluster, execute the following command in the TiDB client:
```
alter table <db-name>.<table-name> set tiflash replica 0;
```
Wait for the TiFlash replicas of the related tables to be deleted. Check the table replication progress and the replicas are deleted if the replication information of the related tables is not found.

2. Perform the scale-in operation

Next, perform the scale-in operation with one of the following solutions.

Solution 1: Use TiUP to remove a TiFlash node

First, confirm the name of the node to be taken down:
```
tiup cluster display <cluster-name>
```
Remove the TiFlash node (assume that the node name is 10.0.1.4:9000 from Step 1):
```
tiup cluster scale-in <cluster-name> --node 10.0.1.4:9000
```

Solution 2: Manually remove a TiFlash node

In special cases (such as when a node needs to be forcibly taken down), or if the TiUP scale-in operation fails, you can manually remove a TiFlash node with the following steps.

Use the store command of pd-ctl to view the store ID corresponding to this TiFlash node.
- Enter the store command in pd-ctl (the binary file is under resources/bin in the tidb-ansible directory).
- If you use TiUP deployment, replace pd-ctl with tiup ctl:<cluster-version> pd:
```
tiup ctl:<cluster-version> pd -u http://<pd_ip>:<pd_port> store
```
  Note
  If multiple PD instances exist in the cluster, you only need to specify the IP address:port of an active PD instance in the above command.
Remove the TiFlash node in pd-ctl:
- Enter store delete <store_id> in pd-ctl (<store_id> is the store ID of the TiFlash node found in the previous step.
- If you use TiUP deployment, replace pd-ctl with tiup ctl:<cluster-version> pd:
```
tiup ctl:<cluster-version> pd -u http://<pd_ip>:<pd_port> store delete <store_id>
```
  Note
  If multiple PD instances exist in the cluster, you only need to specify the IP address:port of an active PD instance in the above command.
Wait for the store of the TiFlash node to disappear or for the state_name to become Tombstone before you stop the TiFlash process.
If, after waiting for a long time, the node still fails to disappear or the state_name fails to become Tombstone, consider using the following command to force the node out of the cluster (use with caution).
Warning
- The following command directly discards the replicas on the TiFlash node, which might cause the query to fail.
- Once you have used this command, do not use PD Control to delete the node from the metadata of PD. Otherwise, the information of Regions in the cluster will be inconsistent.
- The following command is only applicable to TiFlash nodes. Do not use this command to force any TiKV node out of the cluster. Otherwise, data loss occurs.
- After using this command, because the information of the replicas on the forced-out node still exists in the member information of other replicas, PD triggers scheduling to repair and clear the replica information of the forced-out node. Therefore, before using this command, you need to consider whether there are enough replicas to elect a leader after losing the nodes. Otherwise, PD cannot trigger scheduling to repair and clear the information, which causes the service to be unavailable.
```
curl -X POST 'http://<pd-address>/pd/api/v1/store/<store_id>/state?state=Tombstone'
```
Manually delete TiFlash data files (whose location can be found in the data_dir directory under the TiFlash configuration of the cluster topology file).
Manually update TiUP's cluster configuration file (delete the information of the TiFlash node that goes down in edit mode).
```
tiup cluster edit-config <cluster-name>
```

Note

Before all TiFlash nodes in the cluster stop running, if not all tables replicated to TiFlash are canceled, you need to manually clean up the replication rules in PD, or the TiFlash node cannot be taken down successfully.

The steps to manually clean up the replication rules in PD are below:

View all data replication rules related to TiFlash in the current PD instance:

curl http://<pd_ip>:<pd_port>/pd/api/v1/config/rules/group/tiflash

[
  {
    "group_id": "tiflash",
    "id": "table-45-r",
    "override": true,
    "start_key": "7480000000000000FF2D5F720000000000FA",
    "end_key": "7480000000000000FF2E00000000000000F8",
    "role": "learner",
    "count": 1,
    "label_constraints": [
      {
        "key": "engine",
        "op": "in",
        "values": [
          "tiflash"
        ]
      }
    ]
  }
]

Remove all data replication rules related to TiFlash. Take the rule whose id is table-45-r as an example. Delete it by the following command:
```
curl -v -X DELETE http://<pd_ip>:<pd_port>/pd/api/v1/config/rule/tiflash/table-45-r
```

Scale in a TiCDC cluster

If you want to remove the TiCDC node from the 10.0.1.4 host, take the following steps:

Take the node offline:

tiup cluster scale-in <cluster-name> --node 10.0.1.4:8300

View the cluster status:
```
tiup cluster display <cluster-name>
```
Access the monitoring platform at http://10.0.1.5:3000 using your browser, and view the status of the cluster.

The current topology is as follows:

Host IP	Service
10.0.1.3	TiDB + TiFlash + TiCDC
10.0.1.4	TiDB + PD + (TiCDC is deleted）
10.0.1.5	TiDB + Monitor
10.0.1.1	TiKV
10.0.1.2	TiKV