74 lines
3.2 KiB
SYSTEMD
74 lines
3.2 KiB
SYSTEMD
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# This systemd unit puts the PostgreSQL storage on tmpfs and (tries to) sync
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# it back at shutdown.
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# Of course, in case of power failure or any problem preventing this
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# unit to stop properly and sync back the data to disk : DATA LOSS.
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# To install :
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# - apt install rsync
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# - copy this file to /etc/systemd/system/postgresqlontmpfs@.service
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# - in the following lines, replace NN-xxxx by the version and cluster name targeted, for example: postgresqlontmpfs@15-main
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# - systemctl enable postgresqlontmpfs@NN-xxxx
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# - systemctl stop postgresql
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# - systemctl start postgresqlontmpfs@NN-xxxxx
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# - systemctl start postgresql
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# This file is free software licensed under the WTFPL (v2)
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# DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
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# Version 2, December 2004
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#
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# Copyright (C) 2004 Sam Hocevar <sam@hocevar.net>
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#
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# Everyone is permitted to copy and distribute verbatim or modified
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# copies of this license document, and changing it is allowed as long
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# as the name is changed.
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#
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# DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
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# TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
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#
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# 0. You just DO WHAT THE FUCK YOU WANT TO.
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[Unit]
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Description=Put /var/lib/postgresql/%I on tmpfs before PostgreSQL starts
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Before=postgresql@%i.service
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ConditionPathIsDirectory=/var/lib/postgresql/%I
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ConditionPathExists=/usr/bin/rsync
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[Install]
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WantedBy=multi-user.target
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[Service]
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Type=oneshot
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RemainAfterExit=yes
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Restart=no
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# We double-check that PostgreSQL is not running before doing anything
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# Per https://www.freedesktop.org/software/systemd/man/systemd.service.html
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# when an ExecCondition= command exits with exit code 1 through 254
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# (inclusive), the remaining commands are skipped and the unit is not marked as
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# failed. However, if an ExecCondition= command exits with 255 or abnormally
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# (e.g. timeout, killed by a signal, etc.), the unit will be considered failed
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# (and remaining commands will be skipped).
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ExecCondition=/bin/sh -c "systemctl --quiet is-active postgresql@%i && echo 'PostgreSQL still active' && exit 255 || exit 0"
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# If the ON-DISK directory doesn't exist, simply rename /var/lib/postgresql/NN/main to
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# /var/lib/postgresql/NN/main.ON-DISK and recreate /var/lib/postgresql/NN/main
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ExecStart=/bin/sh -c "if [ ! -e /var/lib/postgresql/%I.ON-DISK ] ; then mv -v /var/lib/postgresql/%I /var/lib/postgresql/%I.ON-DISK && mkdir -v /var/lib/postgresql/%I && chown -v postgres:postgres /var/lib/postgresql/%I; fi"
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# Mount the tmpfs
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# (note: to forcefully limit memory consumption, we can add 'size=1024M' to the mount options)
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ExecStart=/bin/mount -v -t tmpfs -o uid=postgres,gid=postgres,mode=0755 none /var/lib/postgresql/%I
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# Copy the ON-DISK content to the tmpfs
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ExecStart=/usr/bin/rsync -avH --delete /var/lib/postgresql/%I.ON-DISK/ /var/lib/postgresql/%I/
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# At stop :
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# - Little notice for the logs
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ExecStop=/bin/sh -c "echo 'Syncing tmpfs:/var/lib/postgresql/%i to disk'"
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# - fetch back the in-memory data to disk
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ExecStop=/usr/bin/rsync -avH --delete /var/lib/postgresql/%I/ /var/lib/postgresql/%I.ON-DISK/
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# - destroy the tmpfs
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ExecStop=/bin/umount -v /var/lib/postgresql/%I
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# - put back the on-disk storage in its original path
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ExecStop=/bin/sh -c "rmdir -v /var/lib/postgresql/%I && mv -v /var/lib/postgresql/%I.ON-DISK /var/lib/postgresql/%I"
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