CentOS 7.2 Azure VM – MariaDB/Apache killing memory

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I have an Azure VM with CentOS 7.1, Apache 2.4.6, and MariaDB 5.5. The VM has 2 cores and 3.5 GB RAM. The server is only hosting a small WordPress site with almost no traffic.

For the past two days, MariaDB constantly crashes with an OOM error. I’ve tried so many different things for tweaking performance and so far absolutely nothing has helped. This is the current config from the my.cnf file:

[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
# Settings user and group are ignored when systemd is used.
# If you need to run mysqld under a different user or group,
# customize your systemd unit file for mariadb according to the
# instructions in http://fedoraproject.org/wiki/Systemd
performance_schema = off
innodb_buffer_pool_size = 1024M
key_buffer_size = 50M

[mysqld_safe]
log-error=/var/log/mariadb/mariadb.log
pid-file=/var/run/mariadb/mariadb.pid

The Apache is a prefork version and I’ve added the following tweaks:

KeepAlive On
KeepAliveTimeout 3

StartServers 1
MinSpareServers 3
MaxSpareServers 6
ServerLimit 24
MaxClients 24
MaxRequestsPerChild 3000

I’ve tried with the default settings too and it makes no difference. Here is a sampling of the errors from the MariaDB log:

160124 15:04:53 mysqld_safe Number of processes running now: 0
160124 15:04:53 mysqld_safe mysqld restarted
160124 15:05:47 [Note] /usr/libexec/mysqld (mysqld 5.5.44-MariaDB) starting as process 4014 ...
160124 15:05:47 InnoDB: The InnoDB memory heap is disabled
160124 15:05:47 InnoDB: Mutexes and rw_locks use GCC atomic builtins
160124 15:05:47 InnoDB: Compressed tables use zlib 1.2.7
160124 15:05:47 InnoDB: Using Linux native AIO
160124 15:05:48 InnoDB: Initializing buffer pool, size = 128.0M
InnoDB: mmap(137756672 bytes) failed; errno 12
160124 15:05:48 InnoDB: Completed initialization of buffer pool
160124 15:05:48 InnoDB: Fatal error: cannot allocate memory for the buffer pool
160124 15:05:48 [ERROR] Plugin 'InnoDB' init function returned error.
160124 15:05:48 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
160124 15:05:48 [ERROR] mysqld: Out of memory (Needed 128917504 bytes)
160124 15:05:48 [ERROR] mysqld: Out of memory (Needed 96681984 bytes)
160124 15:05:48 [ERROR] mysqld: Out of memory (Needed 72499200 bytes)
160124 15:05:51 [Note] Plugin 'FEEDBACK' is disabled.
160124 15:05:52 [ERROR] Unknown/unsupported storage engine: InnoDB
160124 15:05:52 [ERROR] Aborting

What can I do? I have other VM’s in Azure with the same specs and running many more, and more complex, sites, and they have zero crashes.

EDIT This is what the memory looks like within one minute of starting up MariaDB:

[root@linuxvm admin]# systemctl start mariadb
[root@linuxvm admin]# free -m
              total        used        free      shared  buff/cache   available
Mem:           3442         670        2573           2         198        2577
Swap:           511          68         443
[root@linuxvm admin]# free -m
              total        used        free      shared  buff/cache   available
Mem:           3442        1181        2052           2         207        2059
Swap:           511          64         447
[root@linuxvm admin]# free -m
              total        used        free      shared  buff/cache   available
Mem:           3442        1523        1709           2         209        1715
Swap:           511          64         447
[root@linuxvm admin]# free -m
              total        used        free      shared  buff/cache   available
Mem:           3442        1829        1397           2         214        1404
Swap:           511          64         447
[root@linuxvm admin]# free -m
              total        used        free      shared  buff/cache   available
Mem:           3442        2713         506           2         222         515
Swap:           511          63         448
[root@linuxvm admin]# free -m
              total        used        free      shared  buff/cache   available
Mem:           3442        3206          93           2         143          59
Swap:           511          63         448

Answer

I’ll just put this here in case someone else needs it cause I literally just stumbled upon the answer now through trial and error, after an entire day of troubleshooting this issue. I read so many posts and blogs and none of them recommended adding the max_connections directive to my.cnf.

After adding the following lines, all my issues cleared up and MariaDB/MySQL stopped hogging all the memory. Your values may need to be adjusted for your specific scenario.

[mysqld]
max_connections = 50
innodb_buffer_pool_size = 1024M

Attribution
Source : Link , Question Author : blizz , Answer Author : blizz

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