Description:
The documentation and the code are inconsistent wrt. back_log
variable.
Code:
/* Fix back_log */
if (back_log == 0 && (back_log= 50 + max_connections / 5) > 900)
back_log= 900;
static Sys_var_ulong Sys_back_log(
"back_log", "The number of outstanding connection requests "
"MySQL can have. This comes into play when the main MySQL thread "
"gets very many connection requests in a very short time",
READ_ONLY GLOBAL_VAR(back_log), CMD_LINE(REQUIRED_ARG),
VALID_RANGE(0, 65535), DEFAULT(0), BLOCK_SIZE(1));
===================================================================
Documentation: (https://dev.mysql.com/doc/refman/5.6/en/server-system-variables.html#sysvar_back_log )
..
-1 (autosized)
....
As of MySQL 5.6.6, the default value is based on the following formula, capped to a limit of 900:
50 + (max_connections / 5)
Before 5.6.6, the default is 50.
----------------------------------------------------------------------------
So,
a) Instead of 0, it should be -1 in the code for DEFAULT and also
in the 'if', to allow for auto-sizing.
b) The code, currently, doesn't allow for back_log of 0, which
allows the system to define the queue based on SOMAXCONN -- refer to
http://linux.die.net/man/3/listen -- "A backlog argument of 0 may allow
the socket to accept connections, in which case the length of the listen
queue may be set to an implementation-defined minimum value. "
So, the documentation is correct here, but the code isn't.
How to repeat:
N/A
Suggested fix:
Fix the code.
Description: The documentation and the code are inconsistent wrt. back_log variable. Code: /* Fix back_log */ if (back_log == 0 && (back_log= 50 + max_connections / 5) > 900) back_log= 900; static Sys_var_ulong Sys_back_log( "back_log", "The number of outstanding connection requests " "MySQL can have. This comes into play when the main MySQL thread " "gets very many connection requests in a very short time", READ_ONLY GLOBAL_VAR(back_log), CMD_LINE(REQUIRED_ARG), VALID_RANGE(0, 65535), DEFAULT(0), BLOCK_SIZE(1)); =================================================================== Documentation: (https://dev.mysql.com/doc/refman/5.6/en/server-system-variables.html#sysvar_back_log ) .. -1 (autosized) .... As of MySQL 5.6.6, the default value is based on the following formula, capped to a limit of 900: 50 + (max_connections / 5) Before 5.6.6, the default is 50. ---------------------------------------------------------------------------- So, a) Instead of 0, it should be -1 in the code for DEFAULT and also in the 'if', to allow for auto-sizing. b) The code, currently, doesn't allow for back_log of 0, which allows the system to define the queue based on SOMAXCONN -- refer to http://linux.die.net/man/3/listen -- "A backlog argument of 0 may allow the socket to accept connections, in which case the length of the listen queue may be set to an implementation-defined minimum value. " So, the documentation is correct here, but the code isn't. How to repeat: N/A Suggested fix: Fix the code.