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Scale PD Microservices Nodes Using TiUP

This document describes how to scale PD microservice nodes (including TSO and Scheduling nodes) in a cluster and how to switch the PD working mode using TiUP.

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

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

Host IP	Service
10.0.1.4	TiDB + PD
10.0.1.5	TiKV + Monitor
10.0.1.1	TiKV
10.0.1.2	TiKV
10.0.1.6	TSO
10.0.1.7	Scheduling

Add TSO/Scheduling nodes

Note

To add TSO/Scheduling nodes to a TiDB cluster that have not enabled PD microservices yet, follow the instructions in Switch from regular mode to microservices mode instead.

This section exemplifies how to add a TSO node (at IP address 10.0.1.8) and a Scheduling node (at IP address 10.0.1.9) to a TiDB cluster with PD microservices enabled.

1. Configure the scale-out topology

Note

By default, the port and directory information is not required. However, in the case of multiple instances on a single machine, you need to allocate different ports and directories for these instances. If the ports or directories have conflicts, you will receive a notification during deployment or scaling.
Starting from TiUP v1.0.0, the scale-out configuration inherits the global configuration of the original cluster.

Add the scale-out topology configuration in the scale-out.yml file:

vi scale-out.yml

The following is the configuration example for the TSO node:

tso_servers:
  - host: 10.0.1.8
    port: 3379

The following is the configuration example for the Scheduling node:

scheduling_servers:
  - host: 10.0.1.9
    port: 3379

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.yml, it also takes effect in scale-out.yml.

2. Run the scale-out command

Before you run the scale-out command, use the check and check --apply commands to detect and automatically repair potential risks in the cluster:

Check for potential risks:

tiup cluster check <cluster-name> scale-out.yml --cluster --user root [-p] [-i /home/root/.ssh/gcp_rsa]

Enable automatic repair:

tiup cluster check <cluster-name> scale-out.yml --cluster --apply --user root [-p] [-i /home/root/.ssh/gcp_rsa]

Run the scale-out command:

tiup cluster scale-out <cluster-name> scale-out.yml [-p] [-i /home/root/.ssh/gcp_rsa]

In the preceding commands:

scale-out.yml is the scale-out configuration file.
--user root indicates logging in to the target machine as the root user to complete the cluster scale out. The root user is expected to have ssh and sudo privileges to the target machine. Alternatively, you can use other users with ssh and sudo privileges to complete the deployment.
[-i] and [-p] are optional. If you have configured login to the target machine without a password, these parameters are not required. If not, choose one of the two parameters. [-i] is the private key of the root user (or other users specified by --user) that has access to the target machine. [-p] is used to input the user password interactively.

If you see Scaled cluster <cluster-name> out successfully, the scale-out operation succeeds.

3. 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 nodes.

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

Host IP	Service
10.0.1.4	TiDB + PD
10.0.1.5	TiKV + Monitor
10.0.1.1	TiKV
10.0.1.2	TiKV
10.0.1.6	TSO
10.0.1.7	Scheduling
10.0.1.8	TSO
10.0.1.9	Scheduling

Remove TSO/Scheduling nodes

Note

For a cluster with PD microservices enabled, if you need to switch it to non-microservice mode, follow the instructions in Switch from microservices mode to regular mode instead.

This section exemplifies how to remove a TSO node (at IP address 10.0.1.8) and a Scheduling node (at IP address 10.0.1.9) from a TiDB cluster with multiple TSO or Scheduling nodes.

1. View the node ID information

tiup cluster display <cluster-name>

Starting /root/.tiup/components/cluster/v1.16/cluster display <cluster-name>

TiDB Cluster: <cluster-name>

TiDB Version: v8.2.0

ID       Role         Host    Ports                            Status  Data Dir        Deploy Dir

--       ----         ----      -----                            ------  --------        ----------

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

10.0.1.4:4000  tidb        10.0.1.4    4000/10080                      Up      -                 deploy/tidb-4000

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    9093/9094                        Up      data/alertmanager-9093 deploy/alertmanager-9093

10.0.1.6:3379  tso          10.0.1.6    3379                            Up|P     data/tso-3379     deploy/tso-3379

10.0.1.8:3379  tso          10.0.1.8    3379                            Up       data/tso-3379    deploy/tso-3379

10.0.1.7:3379  scheduling   10.0.1.7    3379                            Up|P     data/scheduling-3379     deploy/scheduling-3379

10.0.1.9:3379  scheduling   10.0.1.9    3379                            Up       data/scheduling-3379     deploy/scheduling-3379

2. Run scale-in commands

tiup cluster scale-in <cluster-name> --node 10.0.1.8:3379
tiup cluster scale-in <cluster-name> --node 10.0.1.9:3379

The --node parameter is the ID of the node to be taken offline.

If you see Scaled cluster <cluster-name> in successfully, the scale-in operation succeeds.

3. Check the cluster status

Run the following command to check if the nodes are successfully removed:

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 entire cluster.

After the scale-in, the current topology is as follows:

Host IP	Service
10.0.1.4	TiDB + PD
10.0.1.5	TiKV + Monitor
10.0.1.1	TiKV
10.0.1.2	TiKV
10.0.1.6	TSO
10.0.1.7	Scheduling

Switch the PD working mode

You can switch PD services between the following two working modes:

Regular mode: provides routing service, timestamp allocation, and cluster scheduling functions solely by PD nodes.
Microservice mode: enables you to deploy the PD timestamp allocation function to TSO nodes (providing tso microservices) and the cluster scheduling function to Scheduling nodes (providing scheduling microservices) separately. In this way, these two functions are decoupled from the routing function of PD, which allows PD nodes to focus on the routing service for metadata.

Note

During the mode switching, PD services will be unavailable for a few minutes.

Switch from regular mode to microservices mode

For a cluster that has not enabled PD microservices, you can switch it to PD microservice mode and add a TSO node (at IP address 10.0.1.8) and a Scheduling node (at IP address 10.0.1.9) to it as follows:

Add the scale-out topology configuration in the scale-out.yml file:

vi scale-out.yml

The following is a configuration example:

tso_servers:
  - host: 10.0.1.8
    port: 3379
scheduling_servers:
  - host: 10.0.1.9
    port: 3379

Modify the cluster configuration and switch the cluster to PD microservice mode:

tiup cluster edit-config <cluster-name>

Add pd_mode: ms to global:

global:
  user: tidb
   ssh_port: 22
   listen_host: 0.0.0.0
   deploy_dir: /tidb-deploy
   data_dir: /tidb-data
   os: linux
   arch: amd64
   systemd_mode: system
   pd_mode: ms

Perform a rolling update of the PD node configuration:
```
tiup cluster reload <cluster-name> -R pd
```
Note
The PD timestamp allocation service will be unavailable after you run the preceding reload command and will be available again once the scale-out command in the next step completes execution.

Run the scale-out command to add PD microservice nodes:

tiup cluster scale-out <cluster-name> scale-out.yml

Switch from microservices mode to regular mode

For a cluster with PD microservices enabled (assume that it has a TSO node at IP address 10.0.1.8 and a Scheduling node at IP address 10.0.1.9), you can switch it to non-microservice mode as follows:

Modify the cluster configuration and switch the cluster to non-microservice mode:

tiup cluster edit-config <cluster-name>

Remove pd_mode: ms from global:

global:
  user: tidb
   ssh_port: 22
   listen_host: 0.0.0.0
   deploy_dir: /tidb-deploy
   data_dir: /tidb-data
   os: linux
   arch: amd64
   systemd_mode: system

Run the scale-in command to remove all PD microservice nodes:
```
tiup cluster scale-in <cluster-name> --node 10.0.1.8:3379,10.0.1.9:3379
```
Note
The PD timestamp allocation service will be unavailable after you run the preceding scale-in command and will be available again once the reload command in the next step completes execution.
Perform a rolling update of the PD node configuration:
```
tiup cluster reload <cluster-name> -R pd
```

Scale PD Microservices Nodes Using TiUP

Add TSO/Scheduling nodes

1. Configure the scale-out topology

2. Run the scale-out command

3. Check the cluster status

Remove TSO/Scheduling nodes

1. View the node ID information

2. Run scale-in commands

3. Check the cluster status

Switch the PD working mode

Switch from regular mode to microservices mode

Switch from microservices mode to regular mode

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