PostgreSQL continuous backup and PITR with Barman

How can I be ready for the next
backup recovery of a Postgres
database?

Postgres continuous
backup and PITR with
Barman
Gabriele Bartolini
9 December 2020 - Postgres Build 2020

© Copyright EnterpriseDB Corporation, 2020. All rights reserved.3
• PostgreSQL user since ~2000
• Community member since 2006
• 2ndQuadrant, from 2008 to 2020
• Head of Global Support
• Cloud Native Initiative Lead
• Founding member of Barman
• Now with EDB
About Gabriele Bartolini

Today’s menu
• About Barman
• Useful Patterns
• What lies ahead of us
• Final thoughts

Follow me:
@_GBartolini_
Tweet:
#pgbarman
#PostgresBuild2020
pgbarman.org

Eliel Saarinen
“Always design a thing by
considering it in its next larger
context – a chair in a room, a room in
a house, a house in an environment,
an environment in a city plan.”

• Disaster Recovery of PostgreSQL databases
• Based on continuous physical backup
• First backup and recovery tool for PostgreSQL
• Conceived in 2011, open sourced in 2012
• Goal: foster migrations from Oracle
• Written in Python
• Open Source, distributed under GNU GPL 3
About Barman
Backup And Recovery MANager for PostgreSQL

Innovative concepts
First Introduced by Barman in the Postgres ecosystem
• Remote backup
• Remote recovery
• Multiple PostgreSQL servers
• Backup catalogue
• Independent WAL archive and hub
• WAL compression
• Multiple backup methods
• Incremental backup and recovery
• WAL streaming
• Retention policies
• Monitoring integration
• Hook scripts

• Make decisions based on:
• Recovery Point Objectives (RPO)
• Recovery Time Objectives (RTO)
• Your context is unique, and you are the expert there
• Technological aspects are important
• But they are just the means to our business goals
#0 - Focus on business goals
Let goals drive your initiatives, not the technical means

• Resilience
• Commodity storage
• Physical servers with high capacity local disks
• Integration with standby servers
• Zero data loss clusters
#1 - Separate Barman from Postgres
Let Barman and Postgres run on different servers and storage

• File lock issues
• Place “barman_lock_directory” in the local Linux disk
• Performance issues
• Latency
• Throughput (bottleneck)
• Shared storage (variability)
• Accentuated by large databases
#2 - Avoid network disks (if you can)
Some customers run Barman on NFS/CIFS/Ceph/…

• Better resilience of the local cluster
• Next tips will provide the whys and the hows
• Preferably dedicated network
• Data centre as a single point of failure?
• Yes, but ...
• … don’t let that scare you, it can be solved
#3 - Favour locality over distance
Let Barman and Postgres be next to each other, in the same data centre

• Ensure all WALs are shipped
• Rely on replication slots
• Fully automated with “create_slot” option
• Asynchronous replication by default
• Synchronous replication if …
• You add a standby server
#4 - WAL streaming
Let Postgres stream WAL records to Barman and reduce RPO

• On-demand remote fetching:
• Standby servers
• Recovery operations
• “barman-wal-restore”
• Parallel pre-fetch (performance boost)
• On the fly decompression
• Forget about configuring “wal_keep_segments” or “max_wal_size”
#5 - WAL fetching (get-wal)
Use Barman as an “infinite” hub of WAL files through “get-wal”

• Set “compression” option, globally
• Performed by the WAL archiver process
• Invoked automatically by the “cron” command
• gzip is normally fine
• Supported algorithms:
• bzip2
• pigz
• There’s more: custom compression methods
#6 - Compress your WALs

#7 - Your PostgreSQL building block
The “Flux Capacitor” Food for thought:
1. Primary instance
2. Standby instance
3. Barman instance
• High Availability
• Disaster Recovery
• Local standby servers
• You can always add more
• Simple architecture
• Yet very effective
• Symmetric architecture (next rule)

#8 - Multi-data centre architecture
Symmetric architecture is key

#9 - Encryption
Very important for GDPR compliance
Encrypt at rest Food for thought:
• PostgreSQL servers
• Backup servers
• Delegated to the operating system
• LUKS
• Volmetric
• Secure connections
• Secure access to backup servers
• Encryption of exported backup files:
• Tar files on tape
• Tar files on Cloud object stores

#10 - Constrain your RPO
Clearly define your Recovery Point Objective in PostgreSQL
• By default it is approximately a WAL file
• Recommendation: set it to a maximum of 5 minutes
• Use “archive_timeout”
• For example “archive_timeout = 5min”
• Important for geographical redundancy
• Beyond the local region

#11 - Reduce your RPO to 0
Trust PostgreSQL native synchronous streaming replication
• Requirements:
• A local standby
• A local Barman
• Two options:
• Zero data loss standby
• Zero data loss backup

#12 - Backup from a standby
Available from PostgreSQL 9.6
• Symmetric architecture
• Off-load the primary
• Redundancy
• Feature request: cluster
awareness

#13 - Let “check” be your compass
“barman check” is the most critical command
• It guides you
• Setup process
• Problem solving
• Integration with alerting tools

#14 - Monitoring
Observability is fundamental in business continuity environments
• Barman resides on a Linux system
• That system must be under monitoring
• Standard metrics
• Disk usage
• “barman check --nagios all”

#15 - Weekly backups
Define the frequency of backups through cron
• Start with weekly backups
• Evaluate daily backups if you require shorter RTO
• “barman backup all”

#16 - Retention policies
Key capability in disaster recovery solutions
• Automatically purge old backups
• Retention policies based on:
• Redundancy (quantity)
• Recovery window (time, Point of Recoverability)
• Food for thought:
• Delete hook scripts

#17 - Use rsync/SSH for backups
Barman has an optimised copy algorithm based on rsync
• Enables incremental copy
• Set “reuse_backup = link” if your file system supports hard links
• Enables parallel copy
• Set “parallel_jobs” option
• Used for incremental and parallel recovery too
• Real example from a production customer:
• Weekly backup of a 25TB database takes 13 hours to complete
• Reuses over 70% of the previous backup

#18 - Rely on object stores
By … relaying to AWS S3 compatible object stores
Food for thought:• Public/Private/Hybrid cloud
• You can use a gateway too
• Requires Boto3 library
• “barman-cloud-wal-archive” (WALs)
• “barman-cloud-backup” (Backups)
• Removing SPoF for data availability
• Data centre, Provider, Continent,
Planet, … that’s it for now
• Multi-tiered backup and recovery
• Enhanced DR capabilities
• Remember encryption!

#19 - Public cloud, via Barman

#20 - Public cloud, direct

#21 - Local object store with gateway
To be implemented

#22 - Geo-redundancy

#23 - Aggressive start
Enable “immediate_checkpoint”
• Speed up the start of the backup
• Request a checkpoint without waiting for the scheduled one
• Not available when backing up from a standby server

#24 - Precautions
Best practices that increase the resilience through “barman check”
• “minimum_redundancy”
• Safety measure: set it to 1
• “last_backup_maximum_age”
• Based on the backup frequency
• E.g. “1 week” in case of weekly backups
• “max_incoming_wals_queue”
• Let “barman check” fail if your incoming queue of WALs gets too high

#25 - Server configuration files
Ideal for configuration management tools and automation
• Use a separate configuration file per server
• .conf suffix is required
• Place the file in the /etc/barman.conf.d folder
• Hint: add the major PostgreSQL version as a suffix to the file (and server ID)
• SERVER_ID-PGVERSION.conf
• Example: chat-13.conf

#26 - Last version always wins
Always install the latest version of Barman
• Barman is backwards compatible
• Trunk based development
• Comprehensive set of automated tests

#27 - Enjoy convention over configuration
• Most options in Barman:
• Can be set globally in the configuration file
• Can be overridden at server level
• Have default values
• If you use our packages, system configuration is already taken care of
• User
• Cron
• Log rotation

#28 - Get hooked
Integrate Barman with external systems through hook scripts
• Available Before/After certain events
• Two types:
• Standard: in case of failure, no retry
• Retry: in case of failure, retry
• Typical: before WAL archive to relay WAL files in the Cloud
• See “barman-cloud-wal-archive” man page

#29 - Work in small batches
Configure the WAL archiver batch size
• WAL archiver is automatically run by the “cron” command
• Every minute
• Processes incoming WAL files and archives them compressed (if required)
• By default, the batch is unlimited
• Batch size can be set for both standard archiving and streaming channels
• Tune it based on the number of expected WALs between two cron runs
• Good value to start with is between 10 and 100

#30 - JSON output
• Every command supports “-f json”
• Integration with other applications

#31 - Principle Of Least Authority (POLA)
• Avoid using a superuser for Barman
• The “barman” user can be a standard user
• With specific grants for backup and read operations
• barman_streaming can be used for replication connections
• Requirements:
• PostgreSQL 10+
• Barman 2.11+

#32 - Periodically recover your backups
• Use post backup hook scripts to issue a remote recovery
• Use pre recovery scripts to control and prepare remote environments
• Use post recovery scripts to perform data reconciliation and transformation
• You can regenerate a standby server, a reporting/BI database or a QA environment
• The known unknowns:
• Will my backup work?
• How long will it take to recover from a backup (worst case scenario RTO)?
Use hook scripts to systematically recover and test your backups

#33 - Enhance gradually
• Can I achieve Disaster Recovery?
• Can I achieve High Availability?
• Can I achieve Business Continuity?
• What are my RPO and RTO?
• Start with your goals, add components gradually to improve them
• KISS
• Remove your next Single Point of Failure
Consider a cluster with just a PostgreSQL instance and a Barman instance

EDB powers Barman
EDB acquired 2ndQuadrant on 29 Sept 2020
• EDB is committed to Barman
• New leadership, management and dev team
• Original team stepping down after ~ 10 years
• We will serve as advisors
• Focus on Kubernetes integration
• Want a scoop?
• Abhijit Menon-Sen will lead Barman Development
• Sebastiaan Mannem will be the Product Manager

Some ideas
An anticipation of possible future developments
• Barman Operator for Kubernetes
• Stay tuned, lots of cool stuff around the corner!
• Tier-2: compressed/encrypted backups
• tar_retention_policy
• Tier-3: object store backups
• S3_retention_policy
• Seamless integration with pg_verifybackup
• Snapshot backups

Conclusion
• Use these patterns as enablers for dialog in your team.
• Enhance gradually! Focus on the goals, not the means!
• Constrain your RPO and don’t underestimate RPO=0 scenarios
• Test your backups. Always. Measure your RTO. Be ready for the next incident.
• Remember the “Flux capacitor”
• Barman is stable, robust & backwards compatible
• Barman is Open Source

PostgreSQL continuous backup and PITR with Barman

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