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[MDEV-30543] New status variable: max_used_connections_time

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Add variable max_used_connections_time to show the time at which
max_used_connections reached its current value. This is useful for
troubleshooting high connection counts. MySQL 8 has this already.

All new code of the whole pull request, including one or several files
that are either new files or modified ones, are contributed under the BSD-new
license. I am contributing on behalf of my employer Amazon Web Services.
This commit is contained in:
Mikhail Chalov
2023-03-02 16:14:33 -08:00
committed by Daniel Black
parent c4d6d6fd81
commit ada3987948
3 changed files with 69 additions and 1 deletions
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19
mysql-test/main/status.result
View File

@ -447,3 +447,22 @@ Feature_json 2
connection default;
set @@global.concurrent_insert= @old_concurrent_insert;
SET GLOBAL log_output = @old_log_output;
#
# MDEV-30543 New status variable: Max_used_connections_time
#
FLUSH STATUS;
connect con1,localhost,root,,;
connect con2,localhost,root,,;
connection con1;
disconnect con2;
SELECT 'DTVALUE' = 'DTVALUE' AS expect_1;
expect_1
1
connect con3,localhost,root,,;
connect con4,localhost,root,,;
SELECT 'DTVALUE' < 'DTVALUE' as expect_1;
expect_1
1
disconnect con4;
disconnect con3;
disconnect con1;

31
mysql-test/main/status.test
View File

@ -447,3 +447,34 @@ SET GLOBAL log_output = @old_log_output;
# Wait till we reached the initial number of concurrent sessions
--source include/wait_until_count_sessions.inc
--echo #
--echo # MDEV-30543 New status variable: Max_used_connections_time
--echo #
FLUSH STATUS;
connect (con1,localhost,root,,);
--sleep 1
connect (con2,localhost,root,,);
--sleep 1
let $time_1=`SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME LIKE 'max_used_connections_time'`;
--sleep 1
connection con1;
disconnect con2;
--sleep 1
let $time_2=`SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME LIKE 'max_used_connections_time'`;
--replace_regex /[0-9]*-[0-9]*-[0-9]* [0-9]*:[0-9]*:[0-9]*/DTVALUE/
eval SELECT '$time_1' = '$time_2' AS expect_1;
--sleep 1
connect (con3,localhost,root,,);
--sleep 1
connect (con4,localhost,root,,);
--sleep 1
let $time_3=`SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME LIKE 'max_used_connections_time'`;
--replace_regex /[0-9]*-[0-9]*-[0-9]* [0-9]*:[0-9]*:[0-9]*/DTVALUE/
eval SELECT '$time_1' < '$time_3' as expect_1;
disconnect con4;
disconnect con3;
disconnect con1;

20
sql/mysqld.cc
View File

@ -331,6 +331,7 @@ static my_bool opt_debugging= 0, opt_external_locking= 0, opt_console= 0;
static my_bool opt_short_log_format= 0, opt_silent_startup= 0;
ulong max_used_connections;
time_t max_used_connections_time;
static const char *mysqld_user, *mysqld_chroot;
static char *default_character_set_name;
static char *character_set_filesystem_name;
@ -6173,7 +6174,10 @@ void create_new_thread(CONNECT *connect)
uint sum= connection_count + extra_connection_count;
if (sum > max_used_connections)
{
max_used_connections= sum;
max_used_connections_time= time(nullptr);
}
/*
The initialization of thread_id is done in create_embedded_thd() for
@ -7006,9 +7010,20 @@ static int show_heartbeat_period(THD *thd, SHOW_VAR *var, char *buff,
return 0;
}
#endif /* HAVE_REPLICATION */
static int show_max_used_connections_time(THD *thd, SHOW_VAR *var, char *buff,
enum enum_var_type scope)
{
var->type= SHOW_CHAR;
var->value= buff;
get_date(buff, GETDATE_DATE_TIME | GETDATE_FIXEDLENGTH, max_used_connections_time);
return 0;
}
static int show_open_tables(THD *thd, SHOW_VAR *var, char *buff,
enum enum_var_type scope)
{
@ -7484,6 +7499,7 @@ SHOW_VAR status_vars[]= {
{"Master_gtid_wait_timeouts", (char*) offsetof(STATUS_VAR, master_gtid_wait_timeouts), SHOW_LONG_STATUS},
{"Master_gtid_wait_time", (char*) offsetof(STATUS_VAR, master_gtid_wait_time), SHOW_LONG_STATUS},
{"Max_used_connections", (char*) &max_used_connections, SHOW_LONG},
{"Max_used_connections_time",(char*) &show_max_used_connections_time, SHOW_SIMPLE_FUNC},
{"Memory_used", (char*) &show_memory_used, SHOW_SIMPLE_FUNC},
{"Memory_used_initial", (char*) &start_memory_used, SHOW_LONGLONG},
{"Resultset_metadata_skipped", (char *) offsetof(STATUS_VAR, skip_metadata_count),SHOW_LONG_STATUS},
@ -7822,6 +7838,7 @@ static int mysql_init_variables(void)
specialflag= 0;
binlog_cache_use= binlog_cache_disk_use= 0;
max_used_connections= slow_launch_threads = 0;
max_used_connections_time= 0;
mysqld_user= mysqld_chroot= opt_init_file= opt_bin_logname = 0;
prepared_stmt_count= 0;
mysqld_unix_port= opt_mysql_tmpdir= my_bind_addr_str= NullS;
@ -9200,6 +9217,7 @@ void refresh_status(THD *thd)
connections. This is not perfect, but status data is not exact anyway.
*/
max_used_connections= connection_count + extra_connection_count;
max_used_connections_time= time(nullptr);
}
#ifdef HAVE_PSI_INTERFACE