Adding SD unit: mariadbontmpfs.service

systemd-units/mariadbontmpfs.service

@@ -0,0 +1,72 @@
+# This systemd unit puts the MariaDB/MySQL storage on tmpfs and (tries to) sync
+# it back at shutdown.
+
+# Of course, in case of power failure or any problem preventing this
+# unit to stop properly and sync back the data to disk : DATA LOSS.
+
+# To install :
+# - apt install rsync
+# - systemctl stop mariadb
+# - copy this file to /etc/systemd/system/mariadbontmpfs.service
+# - systemctl enable mariadbontmpfs.service
+# - systemctl start mariadbontmpfs.service
+# - systemctl start mariadb
+
+# This file is free software licensed under the WTFPL (v2)
+#         DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
+#                    Version 2, December 2004
+#
+# Copyright (C) 2004 Sam Hocevar <sam@hocevar.net>
+#
+# Everyone is permitted to copy and distribute verbatim or modified
+# copies of this license document, and changing it is allowed as long
+# as the name is changed.
+#
+#            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
+#   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+#
+#  0. You just DO WHAT THE FUCK YOU WANT TO.
+
+[Unit]
+Description=Put /var/lib/mysql on tmpfs before MariaDB/MySQL starts
+Before=mariadb.service mysql.service
+ConditionPathIsDirectory=/var/lib/mysql
+ConditionPathExists=/usr/bin/rsync
+
+
+[Install]
+WantedBy=multi-user.target
+
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+Restart=no
+
+# We double-check that MariaDB is not running before doing anything
+# Per https://www.freedesktop.org/software/systemd/man/systemd.service.html
+# when an ExecCondition= command exits with exit code 1 through 254
+# (inclusive), the remaining commands are skipped and the unit is not marked as
+# failed. However, if an ExecCondition= command exits with 255 or abnormally
+# (e.g. timeout, killed by a signal, etc.), the unit will be considered failed
+# (and remaining commands will be skipped).
+ExecCondition=/bin/sh -c "systemctl --quiet is-active mariadb mysql && echo 'MariaDB or MySQL still active' && exit 255 || exit 0"
+
+# If the ON-DISK directory doesn't exist, simply rename /var/lib/mysql to
+# /var/lib/mysql.ON-DISK and recreate /var/lib/mysql
+ExecStart=/bin/sh -c "if [ ! -e /var/lib/mysql.ON-DISK ] ; then mv -v /var/lib/mysql /var/lib/mysql.ON-DISK && mkdir -v /var/lib/mysql && chown -v mysql:mysql /var/lib/mysql; fi"
+# Mount the tmpfs
+# (note: to forcefully limit memory consumption, we can add 'size=1024M' to the mount options)
+ExecStart=/bin/mount -v -t tmpfs -o uid=mysql,gid=mysql,mode=0755 none /var/lib/mysql
+# Copy the ON-DISK content to the tmpfs
+ExecStart=/usr/bin/rsync -avH --delete /var/lib/mysql.ON-DISK/ /var/lib/mysql/
+
+# At stop :
+# - Little notice for the logs
+ExecStop=/bin/sh -c "echo 'Syncing tmpfs:/var/lib/mysql to disk'"
+# - fetch back the in-memory data to disk
+ExecStop=/usr/bin/rsync -avH --delete /var/lib/mysql/ /var/lib/mysql.ON-DISK/
+# - destroy the tmpfs
+ExecStop=/bin/umount -v /var/lib/mysql
+# - put back the on-disk storage in its original path
+ExecStop=/bin/sh -c "rmdir -v /var/lib/mysql && mv -v /var/lib/mysql.ON-DISK /var/lib/mysql"