First of all, if you have this kind of problem, check MariaDB logs

tail -n 100 /var/log/mariadb/mariadb.log

you may find something like this:

160608 12:08:05 InnoDB: Completed initialization of buffer pool
160608 12:08:05 InnoDB: Fatal error: cannot allocate memory for the buffer pool
160608 12:08:05 [ERROR] Plugin 'InnoDB' init function returned error.
160608 12:08:05 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
160608 12:08:05 [ERROR] mysqld: Out of memory (Needed 128917504 bytes)

After some research I figured out that mysql require a lot resources for performance schema, and disabling it will help on small memory machines. source

sudo vim /etc/my.cnf

add

performance_schema = off

to section

[mysqld]

To ensure that database server will restart on crash, on OS with Systemd like CentOS 7 you need to do following

Open following file for edit

sudo vim /etc/systemd/system/mariadb.service

and add following lines

.include /lib/systemd/system/mariadb.service

[Service]
Restart=always
RestartSec=3

Then you need to restart reload Systemd configuration

sudo systemctl daemon-reload

and restart MariaDB service

systemctl restart mariadb

To ensure that Systemd restarts service you can do following:

ps -ef|grep maria

You will see something like this

mysql    26647 26368  0 Jun12 ?        00:06:22 /usr/libexec/mysqld ....

Try to kill the process using

kill 26647

Wait 3 seconds and check if MariaDB started again

ps -ef|grep maria

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