Important

You are viewing the documentation of an older version of the TiDB database (TiDB v2.1).

It is recommended that you use the latest LTS version of the TiDB database.

Scale the TiDB Cluster Using TiDB Ansible

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

Warning

In decreasing the capacity, if your cluster has a mixed deployment of other services, do not perform the following procedures. The following examples assume that the removed nodes have no mixed deployment of other services.

Assume that the topology is as follows:

NameHost IPServices
node1172.16.10.1PD1
node2172.16.10.2PD2
node3172.16.10.3PD3, Monitor
node4172.16.10.4TiDB1
node5172.16.10.5TiDB2
node6172.16.10.6TiKV1
node7172.16.10.7TiKV2
node8172.16.10.8TiKV3
node9172.16.10.9TiKV4

Increase the capacity of a TiDB/TiKV node

For example, if you want to add two TiDB nodes (node101, node102) with the IP addresses 172.16.10.101 and 172.16.10.102, take the following steps:

  1. Edit the inventory.ini file and the hosts.ini file, and append the node information.

    • Edit the inventory.ini file:

      [tidb_servers]
172.16.10.4
172.16.10.5
172.16.10.101
172.16.10.102

[pd_servers]
172.16.10.1
172.16.10.2
172.16.10.3

[tikv_servers]
172.16.10.6
172.16.10.7
172.16.10.8
172.16.10.9

[monitored_servers]
172.16.10.1
172.16.10.2
172.16.10.3
172.16.10.4
172.16.10.5
172.16.10.6
172.16.10.7
172.16.10.8
172.16.10.9
172.16.10.101
172.16.10.102

[monitoring_servers]
172.16.10.3

[grafana_servers]
172.16.10.3

      Now the topology is as follows:

      NameHost IPServices
      node1172.16.10.1PD1
      node2172.16.10.2PD2
      node3172.16.10.3PD3, Monitor
      node4172.16.10.4TiDB1
      node5172.16.10.5TiDB2
      node101172.16.10.101TiDB3
      node102172.16.10.102TiDB4
      node6172.16.10.6TiKV1
      node7172.16.10.7TiKV2
      node8172.16.10.8TiKV3
      node9172.16.10.9TiKV4

    • Edit the hosts.ini file:

      [servers]
172.16.10.1
172.16.10.2
172.16.10.3
172.16.10.4
172.16.10.5
172.16.10.6
172.16.10.7
172.16.10.8
172.16.10.9
172.16.10.101
172.16.10.102
[all:vars]
username = tidb
ntp_server = pool.ntp.org

  2. Initialize the newly added node.

    1. Configure the SSH mutual trust and sudo rules of the deployment machine on the central control machine:

      ansible-playbook -i hosts.ini create_users.yml -l 172.16.10.101,172.16.10.102 -u root -k

    2. Install the NTP service on the deployment target machine:

      ansible-playbook -i hosts.ini deploy_ntp.yml -u tidb -b

    3. Initialize the node on the deployment target machine:

      ansible-playbook bootstrap.yml -l 172.16.10.101,172.16.10.102
    Note

    If an alias is configured in the inventory.ini file, for example, node101 ansible_host=172.16.10.101, use -l to specify the alias when executing ansible-playbook. For example, ansible-playbook bootstrap.yml -l node101,node102. This also applies to the following steps.

  3. Deploy the newly added node:

    ansible-playbook deploy.yml -l 172.16.10.101,172.16.10.102

  4. Start the newly added node:

    ansible-playbook start.yml -l 172.16.10.101,172.16.10.102

  5. Update the Prometheus configuration and restart the cluster:

    ansible-playbook rolling_update_monitor.yml --tags=prometheus

  6. Monitor the status of the entire cluster and the newly added node by opening a browser to access the monitoring platform: http://172.16.10.3:3000.

You can use the same procedure to add a TiKV node. But to add a PD node, some configuration files need to be manually updated.

Increase the capacity of a PD node

For example, if you want to add a PD node (node103) with the IP address 172.16.10.103, take the following steps:

  1. Edit the inventory.ini file and append the node information to the end of the [pd_servers] group:

    [tidb_servers]
172.16.10.4
172.16.10.5

[pd_servers]
172.16.10.1
172.16.10.2
172.16.10.3
172.16.10.103

[tikv_servers]
172.16.10.6
172.16.10.7
172.16.10.8
172.16.10.9

[monitored_servers]
172.16.10.4
172.16.10.5
172.16.10.1
172.16.10.2
172.16.10.3
172.16.10.103
172.16.10.6
172.16.10.7
172.16.10.8
172.16.10.9

[monitoring_servers]
172.16.10.3

[grafana_servers]
172.16.10.3

    Now the topology is as follows:

    NameHost IPServices
    node1172.16.10.1PD1
    node2172.16.10.2PD2
    node3172.16.10.3PD3, Monitor
    node103172.16.10.103PD4
    node4172.16.10.4TiDB1
    node5172.16.10.5TiDB2
    node6172.16.10.6TiKV1
    node7172.16.10.7TiKV2
    node8172.16.10.8TiKV3
    node9172.16.10.9TiKV4

  2. Initialize the newly added node:

    ansible-playbook bootstrap.yml -l 172.16.10.103

  3. Deploy the newly added node:

    ansible-playbook deploy.yml -l 172.16.10.103

  4. Login the newly added PD node and edit the starting script:

    {deploy_dir}/scripts/run_pd.sh

    1. Remove the --initial-cluster="xxxx" \ configuration.

      Note

      You cannot add the # character at the beginning of the line. Otherwise, the following configuration cannot take effect.

    2. Add --join="http://172.16.10.1:2379" \. The IP address (172.16.10.1) can be any of the existing PD IP address in the cluster.

    3. Manually start the PD service in the newly added PD node:

      {deploy_dir}/scripts/start_pd.sh

    4. Use pd-ctl to check whether the new node is added successfully:

      ./pd-ctl -u "http://172.16.10.1:2379"
      Note

      pd-ctl is a command used to check the number of PD nodes.

  5. Apply a rolling update to the entire cluster:

    ansible-playbook rolling_update.yml

  6. Start the monitor service:

    ansible-playbook start.yml -l 172.16.10.103

  7. Update the Prometheus configuration and restart the cluster:

    ansible-playbook rolling_update_monitor.yml --tags=prometheus

  8. Monitor the status of the entire cluster and the newly added node by opening a browser to access the monitoring platform: http://172.16.10.3:3000.

Decrease the capacity of a TiDB node

For example, if you want to remove a TiDB node (node5) with the IP address 172.16.10.5, take the following steps:

  1. Stop all services on node5:

    ansible-playbook stop.yml -l 172.16.10.5

  2. Edit the inventory.ini file and remove the node information:

    [tidb_servers]
172.16.10.4
#172.16.10.5  # the removed node

[pd_servers]
172.16.10.1
172.16.10.2
172.16.10.3

[tikv_servers]
172.16.10.6
172.16.10.7
172.16.10.8
172.16.10.9

[monitored_servers]
172.16.10.4
#172.16.10.5  # the removed node
172.16.10.1
172.16.10.2
172.16.10.3
172.16.10.6
172.16.10.7
172.16.10.8
172.16.10.9

[monitoring_servers]
172.16.10.3

[grafana_servers]
172.16.10.3

    Now the topology is as follows:

    NameHost IPServices
    node1172.16.10.1PD1
    node2172.16.10.2PD2
    node3172.16.10.3PD3, Monitor
    node4172.16.10.4TiDB1
    node5172.16.10.5TiDB2 removed
    node6172.16.10.6TiKV1
    node7172.16.10.7TiKV2
    node8172.16.10.8TiKV3
    node9172.16.10.9TiKV4

  3. Update the Prometheus configuration and restart the cluster:

    ansible-playbook rolling_update_monitor.yml --tags=prometheus

  4. Monitor the status of the entire cluster by opening a browser to access the monitoring platform: http://172.16.10.3:3000.

Decrease the capacity of a TiKV node

For example, if you want to remove a TiKV node (node9) with the IP address 172.16.10.9, take the following steps:

  1. Remove the node from the cluster using pd-ctl:

    1. View the store ID of node9:

      ./pd-ctl -u "http://172.16.10.1:2379" -d store

    2. Remove node9 from the cluster, assuming that the store ID is 10:

      ./pd-ctl -u "http://172.16.10.1:2379" -d store delete 10

  2. Use pd-ctl to check whether the node is successfully removed:

    ./pd-ctl -u "http://172.16.10.1:2379" -d store 10
    Note

    It takes some time to remove the node. If the status of the node you remove becomes Tombstone, then this node is successfully removed.

  3. After the node is successfully removed, stop the services on node9:

    ansible-playbook stop.yml -l 172.16.10.9

  4. Edit the inventory.ini file and remove the node information:

    [tidb_servers]
172.16.10.4
172.16.10.5

[pd_servers]
172.16.10.1
172.16.10.2
172.16.10.3

[tikv_servers]
172.16.10.6
172.16.10.7
172.16.10.8
#172.16.10.9  # the removed node

[monitored_servers]
172.16.10.4
172.16.10.5
172.16.10.1
172.16.10.2
172.16.10.3
172.16.10.6
172.16.10.7
172.16.10.8
#172.16.10.9  # the removed node

[monitoring_servers]
172.16.10.3

[grafana_servers]
172.16.10.3

    Now the topology is as follows:

    NameHost IPServices
    node1172.16.10.1PD1
    node2172.16.10.2PD2
    node3172.16.10.3PD3, Monitor
    node4172.16.10.4TiDB1
    node5172.16.10.5TiDB2
    node6172.16.10.6TiKV1
    node7172.16.10.7TiKV2
    node8172.16.10.8TiKV3
    node9172.16.10.9TiKV4 removed

  5. Update the Prometheus configuration and restart the cluster:

    ansible-playbook rolling_update_monitor.yml --tags=prometheus

  6. Monitor the status of the entire cluster by opening a browser to access the monitoring platform: http://172.16.10.3:3000.

Decrease the capacity of a PD node

For example, if you want to remove a PD node (node2) with the IP address 172.16.10.2, take the following steps:

  1. Remove the node from the cluster using pd-ctl:

    1. View the name of node2:

      ./pd-ctl -u "http://172.16.10.1:2379" -d member

    2. Remove node2 from the cluster, assuming that the name is pd2:

      ./pd-ctl -u "http://172.16.10.1:2379" -d member delete name pd2

  2. Use Grafana or pd-ctl to check whether the node is successfully removed:

    ./pd-ctl -u "http://172.16.10.1:2379" -d member

  3. After the node is successfully removed, stop the services on node2:

    ansible-playbook stop.yml -l 172.16.10.2

  4. Edit the inventory.ini file and remove the node information:

    [tidb_servers]
172.16.10.4
172.16.10.5

[pd_servers]
172.16.10.1
#172.16.10.2  # the removed node
172.16.10.3

[tikv_servers]
172.16.10.6
172.16.10.7
172.16.10.8
172.16.10.9

[monitored_servers]
172.16.10.4
172.16.10.5
172.16.10.1
#172.16.10.2  # the removed node
172.16.10.3
172.16.10.6
172.16.10.7
172.16.10.8
172.16.10.9

[monitoring_servers]
172.16.10.3

[grafana_servers]
172.16.10.3

    Now the topology is as follows:

    NameHost IPServices
    node1172.16.10.1PD1
    node2172.16.10.2PD2 removed
    node3172.16.10.3PD3, Monitor
    node4172.16.10.4TiDB1
    node5172.16.10.5TiDB2
    node6172.16.10.6TiKV1
    node7172.16.10.7TiKV2
    node8172.16.10.8TiKV3
    node9172.16.10.9TiKV4

  5. Perform a rolling update to the entire TiDB cluster:

    ansible-playbook rolling_update.yml

  6. Update the Prometheus configuration and restart the cluster:

    ansible-playbook rolling_update_monitor.yml --tags=prometheus

  7. To monitor the status of the entire cluster, open a browser to access the monitoring platform: http://172.16.10.3:3000.

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