TiDB Quick Start Guide

About TiDB

TiDB (The pronunciation is: /’taɪdiːbi:/ tai-D-B, etymology: titanium) is a Hybrid Transactional/Analytical Processing (HTAP) database. Inspired by the design of Google F1 and Google Spanner, TiDB features infinite horizontal scalability, strong consistency, and high availability. The goal of TiDB is to serve as a one-stop solution for online transactions and analyses.

About this guide

This guide outlines how to perform a quick deployment of a TiDB cluster using TiDB-Ansible and walks you through the basic TiDB operations and administrations.

Deploy the TiDB cluster

This section describes how to deploy a TiDB cluster. A TiDB cluster consists of different components: TiDB servers, TiKV servers, and Placement Driver (PD) servers.

The architecture is as follows:

TiDB Architecture

For details of deploying a TiDB cluster, see Ansible Deployment.

Try TiDB

This section describes some basic CRUD operations in TiDB.

Create, show, and drop a database

You can use the CREATE DATABASE statement to create a database.

The Syntax is as follows:

CREATE DATABASE db_name [options];

For example, the following statement creates a database with the name samp_db:

CREATE DATABASE IF NOT EXISTS samp_db;

You can use the SHOW DATABASES statement to show the databases:

SHOW DATABASES;

You can use the DROP DATABASE statement to delete a database, for example:

DROP DATABASE samp_db;

Create, show, and drop a table

Use the CREATE TABLE statement to create a table. The Syntax is as follows:

CREATE TABLE table_name column_name data_type constraint;

For example:

CREATE TABLE person (
 number INT(11),
 name VARCHAR(255),
 birthday DATE
);

Add IF NOT EXISTS to prevent an error if the table exists:

CREATE TABLE IF NOT EXISTS person (
 number INT(11),
 name VARCHAR(255),
 birthday DATE
);

Use the SHOW CREATE statement to see the statement that creates the table. For example:

SHOW CREATE table person;

Use the SHOW FULL COLUMNS statement to display the information about all the columns in a table. For example:

SHOW FULL COLUMNS FROM person;

Use the DROP TABLE statement to delete a table. For example:

DROP TABLE person;

or

DROP TABLE IF EXISTS person;

Use the SHOW TABLES statement to show all the tables in a database. For example:

SHOW TABLES FROM samp_db;

Create, show, and drop an index

For the columns whose value is not unique, you can use the CREATE INDEX or ALTER TABLE statements. For example:

CREATE INDEX person_num ON person (number);

or

ALTER TABLE person ADD INDEX person_num (number);

You can also create unique indexes for the columns whose value is unique. For example:

CREATE UNIQUE INDEX person_num ON person (number);

or

ALTER TABLE person ADD UNIQUE person_num (number);

Use the SHOW INDEX to display all the indexes in a table:

SHOW INDEX from person;

Use the ALTER TABLE or DROP INDEX to delete an index. Like the CREATE INDEX statement, DROP INDEX can also be embedded in the ALTER TABLE statement. For example:

DROP INDEX person_num ON person;
ALTER TABLE person DROP INDEX person_num;

Insert, select, update, and delete data

Use the INSERT statement to insert data into a table. For example:

INSERT INTO person VALUES("1","tom","20170912");

Use the SELECT statement to see the data in a table. For example:

SELECT * FROM person;
+--------+------+------------+
| number | name | birthday   |
+--------+------+------------+
|      1 | tom  | 2017-09-12 |
+--------+------+------------+

Use the UPDATE statement to update the data in a table. For example:

UPDATE person SET birthday='20171010' WHERE name='tom';

SELECT * FROM person;
+--------+------+------------+
| number | name | birthday   |
+--------+------+------------+
|      1 | tom  | 2017-10-10 |
+--------+------+------------+

Use the DELETE statement to delete the data in a table. For example:

DELETE FROM person WHERE number=1;
SELECT * FROM person;
Empty set (0.00 sec)

Create, authorize, and delete a user

Use the CREATE USER statement to create a user named tiuser with the password 123456:

CREATE USER 'tiuser'@'localhost' IDENTIFIED BY '123456';

Grant tiuser the privilege to retrieve the tables in the samp_db database:

GRANT SELECT ON samp_db .* TO 'tiuser'@'localhost';

Check the privileges of tiuser:

SHOW GRANTS for tiuser@localhost;

Delete tiuser:

DROP USER 'tiuser'@'localhost';

Monitor the TiDB cluster

Open a browser to access the monitoring platform: http://172.16.10.3:3000.

The default account and password are: admin/admin.

About the key metrics

Service Panel Name Description Normal Range
PD Storage Capacity the total storage capacity of the TiDB cluster
PD Current Storage Size the occupied storage capacity of the TiDB cluster
PD Store Status – up store the number of TiKV nodes that are up
PD Store Status – down store the number of TiKV nodes that are down 0. If the number is bigger than 0, it means some node(s) are not down.
PD Store Status – offline store the number of TiKV nodes that are manually offline
PD Store Status – Tombstone store the number of TiKV nodes that are Tombstone
PD Current storage usage the storage occupancy rate of the TiKV cluster If it exceeds 80%, you need to consider adding more TiKV nodes.
PD 99% completed cmds duration seconds the 99th percentile duration to complete a pd-server request less than 5ms
PD average completed cmds duration seconds the average duration to complete a pd-server request less than 50ms
PD leader balance ratio the leader ratio difference of the nodes with the biggest leader ratio and the smallest leader ratio It is less than 5% for a balanced situation. It becomes bigger when a node is restarting.
PD region balance ratio the region ratio difference of the nodes with the biggest region ratio and the smallest region ratio It is less than 5% for a balanced situation. It becomes bigger when adding or removing a node.
TiDB handle requests duration seconds the response time to get TSO from PD less than 100ms
TiDB tidb server QPS the QPS of the cluster application specific
TiDB connection count the number of connections from application servers to the database Application specific. If the number of connections hops, you need to find out the reasons. If it drops to 0, you can check if the network is broken; if it surges, you need to check the application.
TiDB statement count the number of different types of statement within a given time application specific
TiDB Query Duration 99th percentile the 99th percentile query time
TiKV 99% & 99.99% scheduler command duration the 99th percentile and 99.99th percentile scheduler command duration For 99%, it is less than 50ms; for 99.99%, it is less than 100ms.
TiKV 95% & 99.99% storage async_request duration the 95th percentile and 99.99th percentile Raft command duration For 95%, it is less than 50ms; for 99.99%, it is less than 100ms.
TiKV server report failure message There might be an issue with the network or the message might not come from this cluster. If there are large amount of messages which contains unreachable, there might be an issue with the network. If the message contains store not match, the message does not come from this cluster.
TiKV Vote the frequency of the Raft vote Usually, the value only changes when there is a split. If the value of Vote remains high for a long time, the system might have a severe issue and some nodes are not working.
TiKV 95% and 99% coprocessor request duration the 95th percentile and the 99th percentile coprocessor request duration Application specific. Usually, the value does not remain high.
TiKV Pending task the number of pending tasks Except for PD worker, it is not normal if the value is too high.
TiKV stall RocksDB stall time If the value is bigger than 0, it means that RocksDB is too busy, and you need to pay attention to IO and CPU usage.
TiKV channel full The channel is full and the threads are too busy. If the value is bigger than 0, the threads are too busy.
TiKV 95% send message duration seconds the 95th percentile message sending time less than 50ms
TiKV leader/region the number of leader/region per TiKV server application specific

Scale the TiDB cluster

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:

Name Host IP Services
node1 172.16.10.1 PD1
node2 172.16.10.2 PD2
node3 172.16.10.3 PD3, Monitor
node4 172.16.10.4 TiDB1
node5 172.16.10.5 TiDB2
node6 172.16.10.6 TiKV1
node7 172.16.10.7 TiKV2
node8 172.16.10.8 TiKV3
node9 172.16.10.9 TiKV4

Increase the capacity of a TiDB/TiKV node

For example, if you want to add two TiDB nodes (node101, node102) with the IP address 172.16.10.101 and 172.16.10.102, you can use the following procedures:

  1. Edit the inventory.ini file and append the node information:

    [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:

    Name Host IP Services
    node1 172.16.10.1 PD1
    node2 172.16.10.2 PD2
    node3 172.16.10.3 PD3, Monitor
    node4 172.16.10.4 TiDB1
    node5 172.16.10.5 TiDB2
    node101 172.16.10.101 TiDB3
    node102 172.16.10.102 TiDB4
    node6 172.16.10.6 TiKV1
    node7 172.16.10.7 TiKV2
    node8 172.16.10.8 TiKV3
    node9 172.16.10.9 TiKV4
  2. Initialize the newly added node:

    ansible-playbook bootstrap.yml -l 172.16.10.101,172.16.10.102
    
  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, you can use the following procedures:

  1. Edit the inventory.ini file and append 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
    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:

    Name Host IP Services
    node1 172.16.10.1 PD1
    node2 172.16.10.2 PD2
    node3 172.16.10.3 PD3, Monitor
    node103 172.16.10.103 PD4
    node4 172.16.10.4 TiDB1
    node5 172.16.10.5 TiDB2
    node6 172.16.10.6 TiKV1
    node7 172.16.10.7 TiKV2
    node8 172.16.10.8 TiKV3
    node9 172.16.10.9 TiKV4
  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. Roll upgrade the entire cluster:

    ansible-playbook rolling_update.yml
    
  6. Update the Prometheus configuration and restart the cluster:

    ansible-playbook rolling_update_monitor.yml --tags=prometheus
    
  7. 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, you can use the following procedures:

  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:

    Name Host IP Services
    node1 172.16.10.1 PD1
    node2 172.16.10.2 PD2
    node3 172.16.10.3 PD3, Monitor
    node4 172.16.10.4 TiDB1
    node5 172.16.10.5 TiDB2 removed
    node6 172.16.10.6 TiKV1
    node7 172.16.10.7 TiKV2
    node8 172.16.10.8 TiKV3
    node9 172.16.10.9 TiKV4
  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, you can use the following procedures:

  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 Grafana or 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 node9 does not show in the result, the 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:

    Name Host IP Services
    node1 172.16.10.1 PD1
    node2 172.16.10.2 PD2
    node3 172.16.10.3 PD3, Monitor
    node4 172.16.10.4 TiDB1
    node5 172.16.10.5 TiDB2
    node6 172.16.10.6 TiKV1
    node7 172.16.10.7 TiKV2
    node8 172.16.10.8 TiKV3
    node9 172.16.10.9 TiKV4 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, you can use the following procedures:

  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:

    Name Host IP Services
    node1 172.16.10.1 PD1
    node2 172.16.10.2 PD2 removed
    node3 172.16.10.3 PD3, Monitor
    node4 172.16.10.4 TiDB1
    node5 172.16.10.5 TiDB2
    node6 172.16.10.6 TiKV1
    node7 172.16.10.7 TiKV2
    node8 172.16.10.8 TiKV3
    node9 172.16.10.9 TiKV4
  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.

Destroy the TiDB cluster

Stop the cluster:

ansible-playbook stop.yml

Destroy the cluster:

ansible-playbook unsafe_cleanup.yml