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3/25/2019 PostgreSQL Backups the Modern Way
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PostgreSQL BackupsPostgreSQL Backupsthe Modern Waythe Modern Way
Nordic PGDay 2019 Copenhagen, Denmark
Magnus Hagander [email protected]
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Magnus HaganderMagnus HaganderRedpill Linpro
Infrastructure servicesPrincipal database consultant
PostgreSQLCore Team memberCommitterPostgreSQL Europe
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So, backups...So, backups...Do you make them?
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BackupsBackupsAre not superseded by replicationOr cloudOr containers..
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BackupsBackupsAre boringBut I'm glad you have them
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BackupsBackupsWhen did you last restore?
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PostgreSQL backupsPostgreSQL backupsOk, enough genericWhat about backups in PostgreSQL?
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Seen this before?Seen this before?pg_dump options:pg_dump options:
-Fc = custom format -Z = compression -j = parallel -a = data only, -s = schema only -n = schema, -t = table ...
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pg_dumppg_dumpDon't use for backups
Has other good usecasesToo slow to restoreToo much overheadNo PITRExceptions, of course
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Physical backupsPhysical backupsBase backupsWith or without log archiveFast restoreFull cluster onlyPlatform specific
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Base backupsBase backups #!/bin/bash set -e psql -U postgres -q "SELECT pg_start_backup('foo')" tar cfz /backup/$(date +%Y%m%d).tar.gz /var/lib/pgsql/data psql -U postgres -q "SELECT pg_stop_backup()"
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Base backupsBase backupsSo many ways to get that wrong
Spot one?
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Base backupsBase backupsThis used to be the only wayMany scripts around that does itMost of those are broken...
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pg_basebackuppg_basebackupBase backup over replication protocolSafeError handling and recoveryFor most cases
(we'll cover other options later)
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pg_basebackuppg_basebackup #!/bin/bash set -e pg_basebackup -D /backup/$(date +%Y%m%d) -Ft
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Needs replicationNeeds replicationEnabled by default in 10!Older versions:
wal_level = hot_standby max_wal_senders = 10
local replication postgres peer
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Backup formatsBackup formatsplain
Safe copy of data directoryNot good with multiple tablespaces
tarDestination still a directoryEach tablespace gets one file
base.tar
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Transaction logTransaction logWAL required to restore backupFrom beginning of backup to endIn the log archive, right?
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Including WALIncluding WALAlways use -x or -X to include WAL
Default in 10Makes backup independently consistent
With or without log archiveMay back up WAL twice
Use even with log archive!
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Including WALIncluding WAL-X fetch
Fetches WAL at end of backupCan fail if WAL rotated
-X streamReplicates WAL over secondary connectionFewer failure scenariosDoes not work with tar prior to version 10
-X noneTurn off (10+ only)
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Replication slotsReplication slotspg_basebackup can fall behind on < 10Use replication slot
Don't forget to drop!PostgreSQL 10 uses ephemeral slot
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Backup compressionBackup compressionpg_basebackup -Z
Compression happens in pg_basebackupTar format onlyCPU usageRemote server?
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Transfer compressionTransfer compressionSSL compression
Much harder these daysssh tunneling
Does not work with WAL ssh mydbserver -c "pg_basebackup -Ft -D- -Z9 -Xnone" > backup.tgz
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That's it!That's it!With that, you have backupsThat workAnd are (reasonably) safe
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PITRPITRPoint in time recoveryYou all want itA bit more setting up
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archive_commandarchive_commandTo use PITR, we use log archivinglike this?
archive_command = 'test ! -f /mnt/archivedir/%f && cp %p /mnt/archivedir/%f'
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Don't do that!Don't do that!
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pg_receivewalpg_receivewalRuns on archive serverUses streaming replicationGenerates log archive
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pg_receivewalpg_receivewalMore granular recoverySafe against server restartsCan follow timeline switches on master
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pg_receivewalpg_receivewalAlways use with replication slot
As of 9.4But we said modern..
Backups should block
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pg_receivewalpg_receivewal pg_receivewal -D /log/archive -h master -S backup
Ensure it's restarted!
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Backup retentionBackup retentionHow long to keep around?What granularity?...
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Backup retentionBackup retentionRecovery needs:
Base backupAll WAL from start to endAll WAL from end to pitr
(that's why we use -x!)
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Backup retentionBackup retentionfind is o�en enoughDelete logs older than X, base older than Y
Safe if -x was used! #!/bin/bash find /var/backups/basebackup -type f -mtime +30 -print0 | xargs -0 -r /bin/rm find /var/backups/wal -type f -mtime +7 -print0 | xargs -0 -r /bin/rm
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Not enough?Not enough?Handles the simple casesBut has limitationsParticularly in management
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Other toolsOther toolspgBackRestBarman
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pgBackRestpgBackRestBackup schedulingLog archivingRetention managementMulti-serverRestore shortcutsObsessive validation
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pgBackRestpgBackRestDeveloped by CrunchyDataPerl
Moving to CMIT licensessh but not rsync
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pgBackRestpgBackRestCustom protocolParallel backups (compression)Full/Differential/Incremental
Segment basedDelta restore
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pgBackRestpgBackRestValidates checksumsChecksums backups
Every time
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pgBackRestpgBackRestNo pg_receivewal support
YetNo Windows support
Yet
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BarmanBarmanBackup schedulingLog archivingRetention managementMulti-serverRestore shortcuts
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BarmanBarmanDeveloped by 2ndQuadrantPythonGPLv3Primarily ssh+rsync
1.6 learned about pg_receivewal2.0 learned about pg_basebackup
Before that, no (safe) concurrent backup support
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What aboutWhat about
Enterprise product XEnterprise product X??
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Enterprise product XEnterprise product Xpg_basebackup
Run as pre-backup commandOptionally clean up in post-backup
pgbackrest/barmanTo diskLet backup so�ware take it form there
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SummarySummary
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Don't roll your own!Don't roll your own!
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Don't roll your ownDon't roll your ownToo many pitfallsBoth base backups and archivingBackups are too important!
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Don't roll your ownDon't roll your ownPrimary choice
Built-in (pg_basebackup)If it's enough
Secondary choicepgBackRestBarman
Tertiary choiceRestart from top of slide
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Thank you!Thank you!Magnus Hagander
[email protected] @magnushagander
https://www.hagander.net/talks/
This material is licensed
