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MySQL

How to set up PMM to monitor a MySQL or MySQL-based database instance.

PMM Client collects metrics from MySQL, Percona Server for MySQL, Percona XtraDB Cluster, and MariaDB. (Amazon RDS is also supported and explained in a separate section.)

Summary

  • Create PMM account and set permissions.
  • Choose a data source:
    • Slow query log, or,
    • Performance Schema.
  • Configure:
    • Query response time,
    • Tablestats,
    • User statistics.
  • Add service.
  • Check service.

Before you start

Check that:

Create a database account for PMM

It is good practice to use a non-superuser account to connect PMM Client to the monitored database instance. This example creates a database user with name pmm, password pass, and the necessary permissions.

On MySQL 8.0

CREATE USER 'pmm'@'localhost' IDENTIFIED BY 'pass' WITH MAX_USER_CONNECTIONS 10;
GRANT SELECT, PROCESS, REPLICATION CLIENT, RELOAD, BACKUP_ADMIN ON *.* TO 'pmm'@'localhost';

On MySQL 5.7

CREATE USER 'pmm'@'localhost' IDENTIFIED BY 'pass' WITH MAX_USER_CONNECTIONS 10;
GRANT SELECT, PROCESS, REPLICATION CLIENT, RELOAD ON *.* TO 'pmm'@'localhost';

Choose and configure a source

Decide which source of metrics to use, and configure your database server for it. The choices are Slow query log and Performance Schema.

While you can use both at the same time we recommend using only one–there is some overlap in the data reported, and each incurs a small performance penalty. The choice depends on the version and variant of your MySQL instance, and how much detail you want to see.

Here are the benefits and drawbacks of Slow query log and Performance Schema metrics sources.

Benefits Drawbacks
Slow query log 1. More detail.
2. Lower resource impact (with query sampling feature in Percona Server for MySQL).
1. PMM Client must be on same host as database server or have access to slow query log.
2. Log files grow and must be actively managed.
Performance Schema 1. Faster parsing.
2. Enabled by default on newer versions of MySQL.
1. Less detail.

Data source recommendations

Database server Versions Recommended source
MySQL 5.1-5.5 Slow query log
MySQL 5.6+ Performance Schema
MariaDB 10.0+ Performance Schema
Percona Server for MySQL 5.7, 8.0 Slow query log
Percona XtraDB Cluster 5.6, 5.7, 8.0 Slow query log

Slow query log

This section covers how to configure a MySQL-based database server to use the slow query log as a source of metrics.

Applicable versions

Server Versions
MySQL 5.1-5.5
MariaDB 10.1.2+
Percona Server for MySQL 5.7.10+, 8.0.12+
Percona XtraDB Cluster 5.6, 5.7, 8.0

The slow query log records the details of queries that take more than a certain amount of time to complete. With the database server configured to write this information to a file rather than a table, PMM Client parses the file and sends aggregated data to PMM Server via the Query Analytics part of PMM Agent.

Settings

Variable Value Description
slow_query_log ON Enables the slow query log.
log_output 'FILE' Ensures the log is sent to a file. (This is the default on MariaDB.)
long_query_time 0 The slow query threshold in seconds. In heavily-loaded applications, many quick queries can affect performance more than a few slow ones. Setting this value to 0 ensures all queries are captured.
log_slow_admin_statements ON Includes the logging of slow administrative statements.
log_slow_slave_statements ON Enables logging for queries that have taken more than long_query_time seconds to execute on the replica.

Examples

  • Configuration file.

    slow_query_log=ON
    log_output=FILE
    long_query_time=0
    log_slow_admin_statements=ON
    log_slow_slave_statements=ON
    
  • Session.

    SET GLOBAL slow_query_log = 1;
    SET GLOBAL log_output = 'FILE';
    SET GLOBAL long_query_time = 0;
    SET GLOBAL log_slow_admin_statements = 1;
    SET GLOBAL log_slow_slave_statements = 1;
    

Slow query log – extended

Some MySQL-based database servers support extended slow query log variables.

Applicable versions
Server Versions
Percona Server for MySQL 5.7.10+, 8.0.12+
Percona XtraDB Cluster 5.6, 5.7, 8.0
MariaDB 10.0
Settings
Variable Value Description
log_slow_rate_limit 100 Defines the rate of queries captured by the slow query log. A good rule of thumb is 100 queries logged per second. For example, if your Percona Server instance processes 10,000 queries per second, you should set log_slow_rate_limit to 100 and capture every 100th query for the slow query log. Depending on the amount of traffic, logging could become aggressive and resource consuming. This variable throttles the level of intensity of the data capture without compromising information.
log_slow_rate_type ‘query’ Set so that it applies to queries, rather than sessions.
slow_query_log_always_write_time 1 Specifies which queries should ignore sampling. With query sampling this ensures that queries with longer execution time will always be captured by the slow query log, avoiding the possibility that infrequent slow queries might not get captured at all.
log_slow_verbosity ‘full’ Ensures that all information about each captured query is stored in the slow query log.
slow_query_log_use_global_control ‘all’ Configure the slow query log during runtime and apply these settings to existing connections. (By default, slow query log settings apply only to new sessions.)
Examples
  • Configuration file (Percona Server for MySQL, Percona XtraDB Cluster).

    log_slow_rate_limit=100
    log_slow_rate_type='query'
    slow_query_log_always_write_time=1
    log_slow_verbosity='full'
    slow_query_log_use_global_control='all'
    
  • Configuration file (MariaDB).

    log_slow_rate_limit=100
    
  • Session (Percona Server for MySQL, Percona XtraDB Cluster).

    SET GLOBAL log_slow_rate_limit = 100;
    SET GLOBAL log_slow_rate_type = 'query';
    SET GLOBAL slow_query_log_always_write_time = 1;
    SET GLOBAL log_slow_verbosity = 'full';
    SET GLOBAL slow_query_log_use_global_control = 'all';
    

Slow query log rotation

Slow query log files can grow quickly and must be managed.

When adding a service with the command line use the pmm-admin option --size-slow-logs to set at what size the slow query log file is rotated. (The size is specified as a number with a suffix. See pmm-admin add mysql.)

When the limit is reached, PMM Client will:

  • remove the previous .old slow log file,
  • rename the current file by adding the suffix .old,
  • execute the MySQL command FLUSH LOGS.

Only one .old file is kept. Older ones are deleted.

You can manage log rotation yourself, for example, with logrotate. If you do, you can disable PMM Client’s log rotation by providing a negative value to --size-slow-logs option when adding a service with pmm-admin add.

Performance Schema

This section covers how to configure a MySQL-based database server to use Performance Schema as a source of metrics.

Applicable versions

Server Versions
Percona Server for MySQL 5.6, 5.7, 8.0
Percona XtraDB Cluster 5.6, 5.7, 8.0
MariaDB 10.3+

PMM’s MySQL Performance Schema Details dashboard charts the various performance_schema metrics.

To use Performance Schema, set these variables.

Variable Value Description
performance_schema ON Enables Performance Schema metrics. This is the default in MySQL 5.6.6 and higher.
performance-schema-instrument 'statement/%=ON' Configures Performance Schema instruments.
performance-schema-consumer-statements-digest ON Configures the statements-digest consumer.
innodb_monitor_enable all Enables InnoDB metrics counters.

Examples

  • Configuration file.

    performance_schema=ON
    performance-schema-instrument='statement/%=ON'
    performance-schema-consumer-statements-digest=ON
    innodb_monitor_enable=all
    
  • Session.

    (performance_schema cannot be set in a session and must be set at server start-up.)

    UPDATE performance_schema.setup_consumers
    SET ENABLED = 'YES' WHERE NAME LIKE '%statements%';
    SET GLOBAL innodb_monitor_enable = all;
    

MariaDB 10.5.7 or lower

There is no Explain or Example data shown by default in Query Analytics when monitoring MariaDB instances version 10.5.7 or lower. A workaround is to set this variable.

Variable Value Description
performance_schema.setup_instruments 'statement/%' List of instrumented object classes.
  • Session.

    UPDATE performance_schema.setup_instruments SET ENABLED = 'YES', TIMED = 'YES' WHERE NAME LIKE 'statement/%';
    UPDATE performance_schema.setup_consumers SET ENABLED = 'YES' WHERE NAME LIKE '%statements%';
    
  • Transactions

    MariaDB doesn’t implement queries history for transactions. All queries executed within a transaction won’t have query examples since PMM relies on the performance_schema.events_statements_history to grab the query example but that table won’t have any query executed as part of a transaction.

    This behavior is because MariaDB doesn’t implement these consumers:

    events_transactions_current
    events_transactions_history
    events_transactions_history_long
    

Query response time

Query time distribution is a chart in the Details tab of Query Analytics showing the proportion of query time spent on various activities. It is enabled with the query_response_time_stats variable and associated plugins.

Applicable versions

Server Versions
Percona Server for MySQL 5.7 (not Percona Server for MySQL 8.0.)
MariaDB 10.0.4

Set this variable to see query time distribution charts.

Variable Value Description
query_response_time_stats ON Report query response time distributions. (Requires plugin installation. See below.)
  • Configuration file.

    query_response_time_stats=ON
    

You must also install the plugins.

  • Session.

    1. Check that /usr/lib/mysql/plugin/query_response_time.so exists.
    2. Install the plugins and activate.

      For MariaDB 10.3:

      INSTALL PLUGIN QUERY_RESPONSE_TIME_AUDIT SONAME 'query_response_time.so';
      INSTALL PLUGIN QUERY_RESPONSE_TIME SONAME 'query_response_time.so';
      SET GLOBAL query_response_time_stats = ON;
      

      For Percona Server for MySQL 5.7:

      INSTALL PLUGIN QUERY_RESPONSE_TIME_AUDIT SONAME 'query_response_time.so';
      INSTALL PLUGIN QUERY_RESPONSE_TIME SONAME 'query_response_time.so';
      INSTALL PLUGIN QUERY_RESPONSE_TIME_READ SONAME 'query_response_time.so';
      INSTALL PLUGIN QUERY_RESPONSE_TIME_WRITE SONAME 'query_response_time.so';
      SET GLOBAL query_response_time_stats = ON;
      

Tablestats

Some table metrics are automatically disabled when the number of tables exceeds a default limit of 1000 tables. This prevents PMM Client from affecting the performance of your database server.

The limit can be changed when adding a service on the command line with the two pmm-admin options:

pmm-admin option Description
--disable-tablestats Disables tablestats collection when the default limit is reached.
--disable-tablestats-limit=N Sets the number of tables (N) for which tablestats collection is disabled. 0 means no limit. A negative number means tablestats is completely disabled (for any number of tables).

User statistics

Applicable versions

User activity, individual table and index access details are shown on the MySQL User Details dashboard when the userstat variable is set.

Server Versions
Percona Server for MySQL 5.6, 5.7, 8.0
Percona XtraDB Cluster 5.6, 5.7, 8.0
MariaDB 5.2.0+

Examples

  • Configuration file.

    userstat=ON
    
  • Session.

    SET GLOBAL userstat = ON;
    

Add service

When you have configured your database server, you can add a MySQL service with the user interface or on the command line.

When adding a service with the command line, you must use the pmm-admin --query-source=SOURCE option to match the source you’ve chosen and configured the database server for.

With the PMM user interface, you select Use performance schema, or deselect it to use slow query log.

With the user interface

  1. Select Configuration PMM Inventory Add Instance.

  2. Select MySQL – Add a remote instance.

  3. Enter or select values for the fields.

  4. Click Add service.

If your MySQL instance is configured to use TLS, click on the Use TLS for database connections check box and fill in your TLS certificates and key.

On the command line

Add the database server as a service using one of these example commands. If successful, PMM Client will print MySQL Service added with the service’s ID and name. Use the --environment and -custom-labels options to set tags for the service to help identify them.

Examples

TLS connection

pmm-admin add mysql --username=user --password=pass --tls --tls-skip-verify --tls-ca=pathtoca.pem --tls-cert=pathtocert.pem --tls-key=pathtocertkey.pem --server-url=http://admin:admin@127.0.0.1 --query-source=perfschema name localhost:3306

Slow query log

Default query source (slowlog), service name ({node name}-mysql), and service address/port (127.0.0.1:3306), with database server account pmm and password pass.

pmm-admin add mysql --username=pmm --password=pass

Slow query log source and log size limit (1 gigabyte), service name (MYSQL_NODE) and service address/port (191.168.1.123:3306).

pmm-admin add mysql --query-source=slowlog --size-slow-logs=1GiB --username=pmm --password=pass MYSQL_NODE 192.168.1.123:3306

Slow query log source, disabled log management (use logrotate or some other log management tool), service name (MYSQL_NODE) and service address/port (191.168.1.123:3306).

pmm-admin add mysql --query-source=slowlog --size-slow-logs=-1GiB --username=pmm --password=pass MYSQL_NODE 192.168.1.123:3306

Default query source (slowlog), service name ({node}-mysql), connect via socket.

pmm-admin add mysql --username=pmm --password=pass --socket=/var/run/mysqld/mysqld.sock

Performance Schema

Performance schema query source, service name (MYSQL_NODE) and default service address/port (127.0.0.1:3306).

pmm-admin add mysql --query-source=perfschema --username=pmm --password=pass MYSQL_NODE

Performance schema query source, service name (MYSQL_NODE) and default service address/port (127.0.0.1:3306) specified with flags.

pmm-admin add mysql --query-source=perfschema --username=pmm --password=pass --service-name=MYSQL_NODE --host=127.0.0.1 --port=3306

Identifying services

Default query source (slowlog), environment labeled test, custom labels setting source to slowlog. (This example uses positional parameters for service name and service address.)

pmm-admin add mysql --environment=test --custom-labels='source=slowlog'  --username=root --password=password --query-source=slowlog MySQLSlowLog localhost:3306

Check the service

PMM user interface

  1. Select Configuration PMM InventoryInventory list.
  2. Look in the Services tab for a matching Service Type (MySQL), Service name, Addresses, and any other details entered in the form.
  3. Look in the Agents tab to check the desired data source is being used.

Command line

Look for your service in the output of this command.

pmm-admin inventory list services --service-type=mysql

Check data

  1. Open the MySQL Instance Summary dashboard.
  2. Set the Service Name to the newly-added service.

Percona Server for MySQL, MariaDB

If query response time plugin was installed, check for data in the MySQL Query Response Time Details dashboard or select a query in PMM Query Analytics to see the Query time distribution bar.

Percona XtraDB Cluster

Open the PXC/Galera Cluster Summary dashboard.


Last update: 2022-05-30