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Diamond custom collector that publishes metrics about MySQL table sizes.

Dependencies

  • MySQLdb
  • MySQL 5.0.3+

Considerations

The information about table sizes is obtained from INFORMATION_SCHEMA.TABLES. As such it is not guaranteed to be 100% accurate, but is subject to the frequency with which the InnoDB and other engines update this information.

Additional concern is the performance impact of running queries against INFORMATION_SCHEMA.TABLES. By default MySQL tries to update table statistics on each access to certain tables from INFORMATION_SCHEMA. This causes delays and needlessly increases the load on the server. In order to stop MySQL from invalidating statistics on every INFORMATION_SCHEMA query you need to set innodb_stats_on_metadata = 0 in your MySQL configuration. You can also set this at runtime because it is a global dynamic variable.

Grants and Privileges

MySQL filters the information visible from information_schema tables based on the access privileges of the user executing the query. Information about database objects that the user is not permitted to access is hidden. To get access to information about all tables from information_schema the MySQL user needs at least REFERENCES privilege on the database (*.*).

In versions of MySQL before 5.5.41, 5.6.22, and 5.7.6, the REFERENCES privilege is marked as 'unused'. After these versions the privilege gives additional access. If REFERENCES privilege is unavailable you will need to grant access (SELECT) to the databases and tables.

Example:

-- Create user for statistics gathering:
CREATE USER `stats`@`localhost` IDENTIFIED BY `somerandompassword`;
-- Grant access to information about tables and databases from information_schema schema
GRANT REFERENCES ON *.* TO 'stats'@'localhost';

-- Grant SELECT on all tables from specific databases
-- GRANT SELECT on database_prod1.* to `stats`@`localhost`;
-- GRANT SELECT on database_prod2.* to `stats`@`localhost`;

Customizing

Diamond looks for collectors in /usr/lib/diamond/collectors/ (on Ubuntu). By default diamond will invoke the collect method every 60 seconds.

There are several ways to configure a python-diamond collector.

The simplest way if you have a single host is to put all the configuration in your diamond.conf in a section named [[MySQLSizeCollector]] under [collectors] section.

[collectors]
...
[[MySQLSizeCollector]]
# enable the collector
enabled = True
# no need to gather statistics more frequently
interval = 600
host = localhost
user = stats
password = stats

The only required configuration parameter is host. All other parameters will be assigned default values if unspecified.

Another way to configure Diamond collectors is to use a separate configuration file placed in /etc/diamond/collectors/. The configuration file name should match the name of the python-diamond collector class. The configuration file for this collector should be named MySQLSizeCollector.conf (/etc/diamond/collectors/MySQLSizeCollector.conf).

The syntax and available parameters in this configuration file is the same as the main diamond.conf file.

Further configuration instructions assume you are using a standalone collector configuration file in /etc/diamond/collectors/MySQLSizeCollector.conf but are also applicable under the [[MySQLSizeCollector]] section in your diamond.conf

In this configuration file you can specify the connection information of your MySQL server. If you don't specify a non-required parameter (everything but "host") it will be assigned a default value. Here is a sample config file:

host = localhost
user = stats
password = stats
db = prod1

In this case MySQLSizeCollector will connect to host localhost with user 'stats' and password 'stats', database 'prod1' with a default connection_timeout of 30 seconds.

If you want to specify the data from more than one MySQL server to be collected, you should put each host in a separate section in your config file. A section is created by putting a string (optionally quoted, if it contains spaces or other non-standard hostname characters) on a new line in square brackets (eg. [server1], [prod-server-sydney]).

Whatever parameters are left unspecified in each section will be set to the corresponding parameters from the root section (top of your config file, without a section) of the config file, if specified, or the built-in default values.

Example configuration file:

user = anotherstat
password = somerandompassword

[master-prod]
host = server1.prod.example.com

[replica1-prod]
host = mysql-slave.prod.example.com
db = prod
port = 3309

[replica2-prod]
host = mysql-slave.sydney.example.com
db = drprod
# this is a host running at the other end of the world, give it more time to respond
connection_timeout = 60
user = drstat

In this particular example the collector will try to obtain table sizes from 'server1.prod.example.com' using username:password 'anotherstat:somerandompassword. The db parameter for this host is not specified, so the connection will be established to information_schema schema, on port 3306 and the connection_timeout will be the default of 30 seconds. The collector will also connect to 'mysql-slave.prod.example.com' on port 3309, database 'prod' using username and password supplied in the root section of the config file ('anotherstat', 'somerandompassword'). Connections to 'mysql-slave.sydney.example.com' host will use port 3306, database 'drprod' and user 'drstat'. The password will be the one supplied in the root configuration section ('somerandompassword').

SSL connections are not implemented yet.

Metrics

By default metrics are collected from each host specified in the configuration file. The metrics that are published are:

  1. table_rows
  2. data_length
  3. index_length
  4. data_free If you don't want to publish any of them you can use the standard configuration parameters [ metrics_whitelist ] and [ metrics_blacklist ] to blacklist or whitelist individual metrics.
Naming

By default all metrics are published using the following hierarchy:

servers.<hostname>.mysql.[alias.]size.<schema>.<table>.<metric>

If you have only one host specified in your configuration file then the [alias] part of the path will be empty. This allows for simpler classification of metrics if you don't need to specify more than one host. If your config file contains sections that specify multiple hosts, then alias will be either the name of the section or the value of the alias configuration option, if supplied.

Each alias is sanitized by replacing ":", ".", "/", and "" with "_" (underscore).