According to the mysql documentation this flag is possible to change dynamically.
Property Value
Command-Line Format --general-log
System Variable general_log
Scope Global
Dynamic Yes
SET_VAR Hint Applies No
Type Boolean
Default Value OFF
But by default this option is disabled. But I need to enable this flag in order to see the logs without restarting the server. What is the way to enable this without restarting the server.
MySQL provides a System variable general_log, which specifies whether the general query log is enabled or not. You will just need to execute the following queries to enable GLOBAL logging (for all the other client sessions as well):
SET GLOBAL general_log = 'ON';
You can also specify the log file path:
SET GLOBAL general_log_file = '/var/log/mysql/all.log';
Remember that when you restart the server, these settings will be lost. To make the changes persistent, you will have to make changes in the configuration file.
If you want to disable the general query logging, you can do the following:
SET GLOBAL general_log = 'OFF'
Related
I wanted to disable the ONLY_FULL_GROUP_BY value of sql-mode permanently even restart the MySQL server. following things I have tried to do but which are not working. that set to the default value when restarting the MySQL.
Persisted settings are permanent. They apply across server restarts.
set PERSIST sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION';
have you tried this?
Using SET GLOBAL to change a variable only changes it for the current MySQL Server process. If the server restarts, changes are reverted. Global variable settings are read from the MySQL Server options file upon startup.
In MySQL 8.0, they added a SET PERSIST command so you can change a global variable and add the setting to the options file at once. Read https://dev.mysql.com/doc/refman/8.0/en/persisted-system-variables.html
If you use an older version of MySQL, you'll have to edit the options file. Editing the options file alone does not change the option in the running MySQL Server instance. You would need to restart the MySQL Server to get it to re-read the options file.
My usual habit is to do both — edit the options file and then also run SET GLOBAL to change it to the same value. That ensures it will be the same after a restart, but it allows me to make the change immediately without restarting.
That said, I recommend you should not disable ONLY_FULL_GROUP_BY. That mode protects you from writing invalid SQL queries.
You can use "SET PERSIST" since MySQL 8.0 to persist "sql_mode" global system variable without ONLY_FULL_GROUP_BY to "mysqld-auto.cnf" as shown below so that "sql_mode" global system variable is not reset after restarting MySQL:
SET PERSIST sql_mode = 'STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION';
In addition, with the command below, you can check all persisted system variables in "mysqld-auto.cnf":
mysql> SELECT * FROM performance_schema.persisted_variables;
+-----------------+----------------------------------------------------------------------------------------------------+
| VARIABLE_NAME | VARIABLE_VALUE |
+-----------------+----------------------------------------------------------------------------------------------------+
| sql_mode | STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION |
| max_connections | 500 |
+-----------------+----------------------------------------------------------------------------------------------------+
And, with the command below, you can remove all persisted system variables from "mysqld-auto.cnf":
RESET PERSIST;
And, with the command below, you can remove only "sql_mode" persisted system variable from "mysqld-auto.cnf":
RESET PERSIST sql_mode;
And, with the command below, you can reset "sql_mode" global system variable:
SET ##GLOBAL.sql_mode = DEFAULT;
Now, "sql_mode" global system variable has the default values with ONLY_FULL_GROUP_BY as shown below:
mysql> SELECT ##GLOBAL.sql_mode;
+-----------------------------------------------------------------------------------------------------------------------+
| ##GLOBAL.sql_mode |
+-----------------------------------------------------------------------------------------------------------------------+
| ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION |
+-----------------------------------------------------------------------------------------------------------------------+
I have an EC2 instance created with a MySQL server instance installed.
Since i am sending large blob data to be stored in the server, and the max_allowed_packet configuration is set to value 1048576, my service requests are failing.
I am trying to increase the size of the parameter to 16MB by using the below command via putty.
SET GLOBAL max_allowed_packet=16777216;
But there is no effect in the parameter. I tried restarting the sql server instance, still the effect isnt seen.
When i run the below command again after setting the parameter, the same old value is shown 1048576.
SHOW VARIABLES LIKE 'max_allowed_packet';
What am i missing here?
Update the MySQL server's configuration file /etc/my.cnf under [mysqld] section with the new value for max_allowed_packet
[mysqld]
max_allowed_packet=16M
and restart the server.
Values set via SET statement are not persisted across server restarts and are applied only on the new client sessions created after the change.
Excerpt from the documentation,
If you change a global system variable, the value is remembered and
used to initialize the session value for new sessions until you change
the variable to a different value or the server exits. The change is
visible to any client that accesses the global value. However, the
change affects the corresponding session value only for clients that
connect after the change. The global variable change does not affect
the session value for any current client sessions (not even the
session within which the global value change occurs).
I set
SET GLOBAL max_allowed_packet=16777216;
and also
[mysqld]
max_allowed_packet = 16M
I checked the max_allowed_packet through below command
SHOW VARIABLES LIKE 'max_allowed_packet';
and the value is = 16777216
But after some days max_allowed_packet automatically reset to 1M.
i am pretty sure that your are hacked. i had the same problem for months. i opened general_log and finally found some codes:
connect root#someipaddress on
Query select 0x4D5A900..........(verylong)
Query select sys_exe('cmd /c c:/windows/nbvqc4.vbs')
.........
set global max_allowed_packet 1024
........
suggestion: change your root password.
MySQL has both GLOBAL variables and SESSION variables, as well as the my.cnf.
GLOBAL variables are initialised on startup from my.cnf, and many variables are taken from the GLOBAL value at connection time and copied into the SESSION. If you change the GLOBAL value, the SESSION keeps it's own value -- but any new sessions will take the new GLOBAL default.
It seems that you did the right thing in terms of setting the GLOBAL variable and updating my.cnf, but in your example you ran "SHOW VARIABLES" which returns the SESSION value. So it is possible you were not checking the correct value in that case. I would recommend for all future checks that you check both the global and session values to help get an idea of what is changing when.
SHOW GLOBAL VARIABLES LIKE 'max_allowed_packet';
SHOW SESSION VARIABLES LIKE 'max_allowed_packet';
For the value to change itself later, the following explanations are possible
(1) You are re-using a session that still has the old value
(2) Another connection has run SET GLOBAL max_allowed_packet, it is possible even that some uncourteous application or script is doing this
(3) The server was restarted, and the my.cnf change is not being applied as expected -- perhaps the file is in the wrong path, or the setting exists more than once in the configuration file. I would check the current Uptime in SHOW GLOBAL STATUS to understand if the server was restarted
I cannot think of any other reasons this would occur. I did check to see if the client negotiates the server-side value when you pass --max_allowed_packet but that does not seem to be the case.
Yes, someone hack the system.I changed the root password and everything working fine.
By default value of max_allowed_packet is 1M in MySQL. I believe size of your "max_allowed_packet" is exceed its upper limit. So, when you check "SHOW VARIABLES LIKE 'max_allowed_packet';" its showing some negative value.
Additionally,
You have two values of max_allowed_packet in MySQL :
one on the client side : [mysql] section, [mysqldump], [client] and more.
one on the server side : [mysqld] section.
Try setting 'Super' privilege of all users to 'N', except 1 admin user. This prevents users from changing max_allowed_packet.
We just ran into this issue and the root cause is we were hacked. Some 3rd party was running a script that was changing the value down.
Tip for those trying to figure out if a hack is a root cause for them - temporarily change your MySQL logging to include all queries. That's how we ended up finding the issue.
I added this line to my.ini
wait_timeout=2000000
When I type
show global variables
It prints wait_timeout=2000000,
but when I type
show variables
It prints wait_timeout=28800
I can set with
set wait_timeout=2000000
But I do not want to set it all the time manually.
Do you have any suggestion to set permanently session system variable?
You probably need to check the interactive_timeout is set also - regular client connections are probably picking up your new setting, but when you check it manually using an interactive client, MySQL will set the timeout from this setting:
On thread startup, the session
wait_timeout value is initialized from
the global wait_timeout value or from
the global interactive_timeout value,
depending on the type of client (as
defined by the CLIENT_INTERACTIVE
connect option to
mysql_real_connect()). See also
interactive_timeout.
See manual for details.
Can I disable general logging completely without restarting the server?
Because, per the documentation:
SET sql_log_bin = {0|1}
Disables or enables binary logging for the current connection (sql_log_bin is a session variable) if the client has the SUPER privilege. The statement is refused with an error if the client does not have that privilege.
Can I enable/disable general log without restarting MySQL?
For anyone using 5.1 now, you can use these commands (had to look them up and this Q&A came up)
SET GLOBAL log_output='TABLE'; #or FILE
SET GLOBAL general_log='OFF'; #or ON
SET GLOBAL slow_query_log='ON'; #or OFF
TABLE will store them in the mysql.general_log and mysql.slow_log tables instead of files which is nice in development for reviewing and truncating.
For MySQL 5.0 "The session sql_log_off variable can be set to ON or OFF to disable or enable general query logging for the current connection." [MySQL Doc, Log file]