Backup on object stores v1
EDB Postgres for Kubernetes natively supports online/hot backup of PostgreSQL clusters through continuous physical backup and WAL archiving on an object store. This means that the database is always up (no downtime required) and that Point In Time Recovery is available.
The operator can orchestrate a continuous backup infrastructure
that is based on the Barman Cloud tool. Instead
of using the classical architecture with a Barman server, which
backs up many PostgreSQL instances, the operator relies on the
barman-cloud-wal-archive
, barman-cloud-check-wal-archive
,
barman-cloud-backup
, barman-cloud-backup-list
, and
barman-cloud-backup-delete
tools. As a result, base backups will
be tarballs. Both base backups and WAL files can be compressed
and encrypted.
For this, it is required to use an image with barman-cli-cloud
included.
You can use the image quay.io/enterprisedb/postgresql
for this scope,
as it is composed of a community PostgreSQL image and the latest
barman-cli-cloud
package.
Important
Always ensure that you are running the latest version of the operands in your system to take advantage of the improvements introduced in Barman cloud (as well as improve the security aspects of your cluster).
A backup is performed from a primary or a designated primary instance in a
Cluster
(please refer to
replica clusters
for more information about designated primary instances), or alternatively
on a standby.
Common object stores
If you are looking for a specific object store such as AWS S3, Microsoft Azure Blob Storage, Google Cloud Storage, or MinIO Gateway, or a compatible provider, please refer to Appendix A - Common object stores.
Retention policies
Important
Retention policies are not currently available on volume snapshots.
EDB Postgres for Kubernetes can manage the automated deletion of backup files from the backup object store, using retention policies based on the recovery window.
Internally, the retention policy feature uses barman-cloud-backup-delete
with --retention-policy “RECOVERY WINDOW OF {{ retention policy value }} {{ retention policy unit }}”
.
For example, you can define your backups with a retention policy of 30 days as follows:
There's more ...
The recovery window retention policy is focused on the concept of
Point of Recoverability (PoR
), a moving point in time determined by
current time - recovery window
. The first valid backup is the first
available backup before PoR
(in reverse chronological order).
EDB Postgres for Kubernetes must ensure that we can recover the cluster at
any point in time between PoR
and the latest successfully archived WAL
file, starting from the first valid backup. Base backups that are older
than the first valid backup will be marked as obsolete and permanently
removed after the next backup is completed.
Compression algorithms
EDB Postgres for Kubernetes by default archives backups and WAL files in an
uncompressed fashion. However, it also supports the following compression
algorithms via barman-cloud-backup
(for backups) and
barman-cloud-wal-archive
(for WAL files):
- bzip2
- gzip
- snappy
The compression settings for backups and WALs are independent. See the DataBackupConfiguration and WALBackupConfiguration sections in the API reference.
It is important to note that archival time, restore time, and size change between the algorithms, so the compression algorithm should be chosen according to your use case.
The Barman team has performed an evaluation of the performance of the supported algorithms for Barman Cloud. The following table summarizes a scenario where a backup is taken on a local MinIO deployment. The Barman GitHub project includes a deeper analysis.
Compression | Backup Time (ms) | Restore Time (ms) | Uncompressed size (MB) | Compressed size (MB) | Approx ratio |
---|---|---|---|---|---|
None | 10927 | 7553 | 395 | 395 | 1:1 |
bzip2 | 25404 | 13886 | 395 | 67 | 5.9:1 |
gzip | 116281 | 3077 | 395 | 91 | 4.3:1 |
snappy | 8134 | 8341 | 395 | 166 | 2.4:1 |
Tagging of backup objects
Barman 2.18 introduces support for tagging backup resources when saving them in
object stores via barman-cloud-backup
and barman-cloud-wal-archive
. As a
result, if your PostgreSQL container image includes Barman with version 2.18 or
higher, EDB Postgres for Kubernetes enables you to specify tags as key-value pairs
for backup objects, namely base backups, WAL files and history files.
You can use two properties in the .spec.backup.barmanObjectStore
definition:
tags
: key-value pair tags to be added to backup objects and archived WAL file in the backup object storehistoryTags
: key-value pair tags to be added to archived history files in the backup object store
The excerpt of a YAML manifest below provides an example of usage of this feature:
Extra options for the backup command
You can append additional options to the barman-cloud-backup
command by using
the additionalCommandArgs
property in the
.spec.backup.barmanObjectStore.data
section.
This property is a list of strings that will be appended to the
barman-cloud-backup
command.
For example, you can use the --read-timeout=60
to customize the connection
reading timeout.
For additional options supported by barman-cloud-backup
you can refer to the
official barman documentation here.
If an option provided in additionalCommandArgs
is already present in the
declared options in the barmanObjectStore
section, the extra option will be
ignored.
The following is an example of how to use this property: