slow query log in default my.cnf (Debian package)

[Jeff Palmer]

The default my.cnf in the debian includes the following:

# Here you can see queries with especially long duration
# log_slow_queries = /var/log/mysql/mysql-slow.log

However, the actual config syntax has changed. If you simply uncomment the line included in the default config, percona server will fail to start.

The new syntax is:

slow_query_log = 1

Unfortunately, even though I've run into this numerous times, it still catches me every single time I set up a new server. Please update the default configs.

P.S. I've only checked the debian packages for 5.5 and 5.6, I have not checked the source tarball, rpm's or other installation methods, nor 5.7.

[Muhammad Irfan (muhammad-irfan)]

I'm able to reproduce this problem for Percona Server 5.6 on Debian Wheezy. I installed Percona Server 5.6 through apt and in my.cnf it used deprecated slow log variable log_slow_queries although commented.

[Muhammad Irfan (muhammad-irfan)]

I tried with Percona Server 5.5.55 via yum install on debian wheezy and I found really strange behavior.

mysql> show global variables like '%version%';
+-------------------------+------------------------------------------------------+
| Variable_name | Value |
+-------------------------+------------------------------------------------------+
| innodb_version | 5.5.55-38.8 |
| protocol_version | 10 |
| slave_type_conversions | |
| tls_version | TLSv1.1,TLSv1.2 |
| version | 5.5.55-38.8-log |
| version_comment | Percona Server (GPL), Release 38.8, Revision 11f5bbd |
| version_compile_machine | x86_64 |
| version_compile_os | debian-linux-gnu |
+-------------------------+------------------------------------------------------+

I un-commented below line from default my.cnf

log_slow_queries = /var/log/mysql/mysql-slow.log

After Percona Server restart

mysql> show global variables like '%slow%';
+------------------------------------+-------------------------------+
| Variable_name | Value |
+------------------------------------+-------------------------------+
| log_slow_admin_statements | OFF |
| log_slow_filter | |
| log_slow_queries | ON |
| log_slow_rate_limit | 1 |
| log_slow_rate_type | session |
| log_slow_slave_statements | OFF |
| log_slow_sp_statements | ON |
| log_slow_verbosity | |
| max_slowlog_files | 0 |
| max_slowlog_size | 0 |
| slow_launch_time | 2 |
| slow_query_log | ON |
| slow_query_log_always_write_time | 10.000000 |
| slow_query_log_file | /var/log/mysql/mysql-slow.log |
| slow_query_log_timestamp_always | OFF |
| slow_query_log_timestamp_precision | second |
| slow_query_log_use_global_control | |
+------------------------------------+-------------------------------+
17 rows in set (0.00 sec)

Slow query log enabled despite of it's disabled from slow log. Further, log_slow_queries should accept ON|OFF bit instead showing value for slow_query_log_file. Other than that, log_slow_queries should be removed completely as slow_query_log is the correct parameter to enable slow log. I'm going to open new bug report for this and this is true for up...

[Muhammad Irfan (muhammad-irfan)]

From https://dev.mysql.com/doc/refman/5.5/en/server-options.html#option_mysqld_log-slow-queries

"The --log-slow-queries option is deprecated and is removed (along with the log_slow_queries system variable) in MySQL 5.6. Instead, use the --slow_query_log option to enable the slow query log and the --slow_query_log_file=file_name option to set the slow query log file name."

Most probably MySQL 5.5 didn't failed with "log_slow_queries" when enabled through my.cnf because "log_slow_queries" is valid in 5.5 version but still my.cnf shouldn't contain below line.

log_slow_queries = /var/log/mysql/mysql-slow.log

And another thing it should be reflecting to value "ON|OFF" instead value for "slow_query_log_file" parameter.

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PS-3534