Monitoring：TiDB database monitoring

HertzBeat monitors general performance metrics of TiDB through HTTP and JDBC protocol.

Metrics Schema

METRICS_SUMMARY

METRICS_TABLES

Protocol Use: HTTP and JDBC

Driver selection

TiDB monitoring keeps the HTTP part unchanged, and the SQL query part now follows the same automatic routing as MySQL:

• If mysql-connector-j is present in ext-lib, the JVM collector or built-in server collector automatically prefers JDBC for the SQL query metric set.
• If mysql-connector-j is absent, HertzBeat automatically uses the built-in MySQL-compatible query engine for the SQL query metric set. No extra JAR is required.
• Restart HertzBeat or the standalone JVM collector after adding or removing a JAR in ext-lib.

Collector package selection

The TiDB template mixes HTTP metrics and MySQL-compatible SQL queries.

• HTTP metric sets are unaffected by JDBC driver selection
• The built-in SQL query engine can collect the default TiDB basic metric set without mysql-connector-j
• If you explicitly place mysql-connector-j in ext-lib, the JVM collector or built-in server collector will still prefer JDBC for the SQL query path

Configuration parameter

Parameter name	Parameter help description
Target Host	Monitored IPV4, IPV6 or domain name. Note⚠️Without protocol header (eg: https://, http://)
Task name	Identify the name of this monitoring. The name needs to be unique
Service Port	The port that the TiDB database provides externally for status reporting is 10080 by default
PD Port	The PD port for the TiDB database, which defaults to 2379
Query timeout	Set the timeout time when SQL query does not respond to data, unit: ms, default: 6000ms
JDBC Port	The TiDB database externally provides the port used for client requests, which defaults to 4000
Database name	Database instance name, optional
Username	Database connection user name, optional
Password	Database connection password, optional
JDBC URL	Database using JDBC connection URL，optional，If configured, the database name, user name, password and other parameters in the URL will overwrite the above configured parameters
Collection interval	Interval time of monitor periodic data collection, unit: second, and the minimum interval that can be set is 30 seconds
Whether to detect	Whether to detect and check the availability of monitoring before adding monitoring. Adding and modifying operations will continue only after the detection is successful
Description remarks	For more information about identifying and describing this monitoring, users can note information here

Collection Metric

The monitoring template will retrieve the monitoring metrics from the TiDB System Variables table, and the user can retrieve the TiDB System Variables Table by himself to query the required information or other system variables.

Besides, TiDB also provides default monitoring metrics table, see Metrics Schema and METRICS_SUMMARY, and users can add their own sql codes according to their needs.

Due to the large number of metrics that can be monitored, only the metrics queried in the monitoring template are described below.

Metric set: global variables

Metric Name	Metric Unit	Metric Help Description
version	none	The MySQL version, followed by the TiDB version. For example '8.0.11-TiDB-v7.5.1'.
version_comment	none	The TiDB version. For example, 'TiDB Server (Apache License 2.0) Community Edition, MySQL 8.0 compatible'.
version_compile_machine	none	The name of the CPU architecture on which TiDB is running.
version_compile_os	none	The name of the OS on which TiDB is running.
max_connections	none	The maximum number of concurrent connections permitted for a single TiDB instance. This variable can be used for resources control. The default value 0 means no limit. When the value of this variable is larger than 0, and the number of connections reaches the value, the TiDB server rejects new connections from clients.
datadir	none	The location where data is stored. This location can be a local path /tmp/tidb, or point to a PD server if the data is stored on TiKV. A value in the format of ${pd-ip}:${pd-port} indicates the PD server that TiDB connects to on startup.
port	none	The port that the tidb-server is listening on when speaking the MySQL protocol.