Mariadb on Centos 7 not changing max connections based on my.cnf

Question

The following configuration in my.cnf is not being followed. Max_connections go back to 151. please help as i have 16gb of dedicated ram that i would like to use properly.

[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
#symbolic-links=0

#vish start
open_files_limit = 8000
max_connections = 500
#set-variable=max_connections=500
thread_concurrency = 8
#concurrent_insert=2
thread_cache_size=2000

interactive_timeout=180
wait_timeout=180

max_allowed_packet = 32M
key_buffer_size = 3000M
read_buffer_size = 16M
read_rnd_buffer_size = 4M
bulk_insert_buffer_size = 256M
myisam_sort_buffer_size = 16M
myisam_max_sort_file_size = 256M
myisam_repair_threads = 1
#myisam_recover = 4
max_heap_table_size = 2048M
tmp_table_size = 1024M
table_open_cache = 2000
table_cache = 2000
sort_buffer_size = 128M 
join_buffer_size = 128M 
query_cache_size = 128M 
query_cache_limit = 128M 

#slow_query_log=1
log-slow-queries
long_query_time=2
#log_queries_not_using_indexes=1
slow_query_log_file = /var/log/mariadb/host_name-slow.log

[mysqldump]
user=root
password=*********
#max_allowed_packet = 1024M 

[myisamchk] 
key_buffer_size = 2500M 
sort_buffer_size = 1024M 
read_buffer = 32M
write_buffer = 32M

[innodb]
innodb_buffer_pool_size=3G
innodb_buffer_pool_instance=2
innodb_additional_mem_pool_size=20M
innodb_log_file_size= 512M
innodb_log_buffer_size=16M
innodb_flush_log_at_trx_commit=1
innodb_thread_concurrency=16
#innodb_read_io_threads=16
#innodb_write_io_threads=16
#innodb_io_capacity=2000
#innodb_lock_wait_timeout=120

innodb_flush_method=O_DIRECT
#vish end

[mysqld_safe]
log-error=/var/log/mariadb/mariadb.log
pid-file=/var/run/mariadb/mariadb.pid
#!includedir /etc/my.cnf.d

Answer 1

Fixed the issue. The issue was to do with the right permissions. The right permissions on the my.cnf file should be 644 not 777.

Answer 2

You might find that the limit is not where you think.

I've had trouble with open file limits and that's set by Centos itself. Please see:

How to permanently raise ulimit 'open files' and MySQL 'open_files_limit'

Some key points from that link:

• The default ulimit on open files is 1024.
• MySQL sets its open_files_limit to whatever the system's ulimit is set to.
• MySQL cannot set it's open_files_limit higher than ulimit.

You can raise the ulimit temporarily or permanently, globally or for specific users; see the link for details.

There are more resources like that around.

Answer 3

check permissions for my.cnf file - ls -l /etc/my.cnf or ls -l /etc/mysql/my.cnf

check owner and group, often when after edit my.cnf it have right for read only for root user

You can change owner to mysql:root or change cmd mask for something like 755, finally You will have:

root@monitor:~# ls -l /etc/mysql/my.cnf
-rwxr-xr-x 1 mysql root 2539 Nov 27 10:10 /etc/mysql/my.cnf
root@monitor:~#

if mysql user can not open my.cnf file - it use default values == 151

Answer 4

There are some other changes to /etc/security/limits.conf and some systemd settings that need to be adjusted. See this article for more details:

https://pjstrnad.com/mariadb-raise-number-of-connections/