Access slow query and general logs for Cloud Databases

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Database logs can be useful tools when analyzing database performance or troubleshooting issues. You can log slow queries or general database activity for a MySQL® Cloud Database instance by attaching a configuration group to the instance and setting the appropriate parameters.

Prerequisites

To follow the steps in this article, you should have an existing MySQL configuration group or create a new one. A MySQL configuration group holds the values for MySQL options used at startup. To learn more about MySQL configuration groups, see Manage configuration groups for cloud databases with the Trove command line tool.

The examples use trove to make changes to configuration groups. You can find instructions for installing and configuring trove in Managing configuration groups for cloud databases with the Trove command-line tool.

To apply configuration groups, you need to enable root access to the database instance. You can do this by using the Cloud Databases API or with a trove command:

    trove root-enable instanceID

Enable the Slow Query Log

You can use the slow query log to find queries that take a long time to execute and are, therefore, candidates for optimization. You can access the MySQL slow query log by writing it to a table and setting persistent values to appropriate parameters in your configuration group.

For more information about the MySQL slow query log, see the MySQL documentation on the slow query log.

To enable the logging of slow queries:

Grant root access to the mysql.slow_log table.
Set the configuration parameters that enable logging slow queries to the mysql.slow_log table:

Parameter name	Suggested value	Description
`log_output`	`'TABLE'`	Tells MySQL to write logs to a table
`slow_query_log`	1	Enables the slow query log

For example, to create a new configuration group with trove that enables slow query logging, run:

trove configuration-create EnableSlowQueryLog '{"log_output":"'TABLE'"}' --datastore MySQL

Optionally, set the configuration parameters that define the conditions under which queries are written to the slow query log:

Parameter name	Suggested value	Description
`long_query_time`	0 or more	The duration of a query to be logged as slow, in seconds. The default is 10 seconds.
`log_queries_not_using_indexes`	0 or 1	Queries that don't use an index, or that perform a full index scan where the index doesn't limit the number of rows, are logged to the slow query log (regardless of the time taken). You need to enable the slow query log for this to have an effect.

For example, run the following command to add parameters to the configuration group created in the previous
step that set the slow query duration to 15 seconds and cause logs to be deleted after one day:

    trove configuration-patch configID '{"long_query_time":15}'

If necessary, attach the configuration group with these parameters to the instance for which you want to enable slow query logging. To attach the configuration by using trove, run:
```
trove configuration-attach instanceID configID
```
After the configuration is applied to your server, you can retrieve the slow query log from the database with a query. For example:
```
mysql -e "select * from mysql.slow_log order by start_time desc limit 1\G"
```

Enable the General Query Log

You can use the general query log to track all activity, including any connections to the database and all queries sent to the database. It can be useful when you want to check the queries sent by a client for troubleshooting purposes.

For more information about the MySQL general query log, see the MySQL documentation on the general query log.

To enable the general query log

Grant root access to the mysql.general_log table.
Set the configuration parameters that enable logging server activity to the mysql.general_log table:

Parameter name	Suggested value	Description
`log_output`	`'TABLE'`	Tells MySQL to write logs to a table

For example, to create a new configuration group with trove that enables general query logging, run:

trove configuration-create EnableGeneralLog '{"log_output":"'TABLE'","slow_query_log":1}' --datastore MySQL

If necessary, attach the configuration group with these parameters to the instance for which you want to enable general query logging. To attach the configuration by using trove, run:
```
trove configuration-attach instanceID configID
```
After the configuration group is attached, you can now enable general logging by running this command:
```
 mysql -e "set global general_log = 1"
```
At the moment, the above variable can only be set dynamically on a running instance due to the overwhelming amount of data this change might generate.

You can also disable general log with the following command:
```
 mysql -e "set global general_log = 0"

	**Note:** General logging is disabled when you restart a MySQL instance.
```
After the configuration is applied to the server, you can retrieve the general query log from the database with a query such as the following example:
```
mysql -e "select * from mysql.general_log order by event_time desc limit 1\G"
```

Updated about 1 year ago