Speedup unit tests by moving MySql data to memory (in Ubuntu) | Wiki

Speedup unit tests by moving MySql data to memory [Ubuntu]

There are several ways to speedup slow unit tests which interact with database:

Refactor code and tests and do not touch db in tests
Use sqlite db in memory instead of MySql
Use MySql MEMORY engine
Move MySql data to memory

Each Method Has Drawbacks:

Not using DB in unit tests means that parts of the code won't be tested.

Using SQLite only for tests may induce different behavior. This is against the very meaning of unit tests.

Like SQLite, the MySQL Memory engine is different from InnoDB and MyISAM. For example, FK are ignored.

The following process moves every MySQL database into a memory filesystem. If you have databases other than the test DB, the copy/restore process may be slow, and you can loose data if something goes wrong. You've been warned, do not use this when you have important data in any database of your MySQL server.

It is better to try other listed approaches and I think of last method as of quick temporary hack, but here it is:

stop mysql
move /var/lib/mysql to /dev/shm/mysql
link /var/lib/mysql to /dev/shm/mysql
start mysql

In Ubuntu there is also a problem with apparmor which will not allow mysql to read from /dev/shm. To fix this it is recommended to add following to the /etc/apparmor.d/usr.sbin.mysqld:

/dev/shm/mysql/ r,
/dev/shm/mysql/** rwk,

But it doesn't work for me and I disabled apparmor for mysql (not recommended):

sudo mv /etc/apparmor.d/usr.sbin.mysqld /etc/apparmor.d/disable

Below are shell scripts to move MySql data to /dev/shm and back, restore backed up data and check db state.

Move db to memory script ¶

#!/bin/sh
#Check if run as root
if [ `whoami` != root ]
then
    echo "You must be root to do that!"
    exit 1
fi
 
service mysql stop
if [ ! -s /var/lib/mysql.backup ]
then
    cp -pRL /var/lib/mysql /var/lib/mysql.backup
fi
mv /var/lib/mysql /dev/shm/mysql
chown -R mysql:mysql /dev/shm/mysql
ln -s /dev/shm/mysql /var/lib/mysql
chown -h mysql:mysql /var/lib/mysql
service mysql start

Move db to disk script ¶

#!/bin/sh
#Check if run as root
if [ `whoami` != root ]
then
    echo "You must be root to do that!"
    exit 1
fi
service mysql stop
rm /var/lib/mysql
if [ ! -s /dev/shm/mysql ]
then
    cp -pRL /var/lib/mysql.backup /var/lib/mysql
else
    mv /dev/shm/mysql /var/lib/mysql
fi
service mysql start

Restore db backup script ¶

#!/bin/sh
#Check if run as root
if [ `whoami` != root ]
then
    echo "You must be root to do that!"
    exit 1
fi
 
service mysql stop
if [ ! -s /var/lib/mysql.backup ]
then
    exit -1
fi
rm /var/lib/mysql
cp -pRL /var/lib/mysql.backup /var/lib/mysql
rm -rf /dev/shm/mysql
service mysql start

Check db state script ¶

#!/bin/sh
#Check if run as root
if [ `whoami` != root ]
then
    echo "You must be root to do that!"
    exit 1
fi
 
if [ -L /var/lib/mysql ]
then
    echo "Mem db"
    exit 0
else
    echo "File db"
    exit 1
fi