WAL archiving v1

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WAL archiving is the process that feeds a WAL archive in EDB Postgres for Kubernetes.

Important

EDB Postgres for Kubernetes currently only supports WAL archives on object stores. Such WAL archives serve for both object store backups and volume snapshot backups.

The WAL archive is defined in the .spec.backup.barmanObjectStore stanza of a Cluster resource. Please proceed with the same instructions you find in the "Backup on object stores" section to set up the WAL archive.

Info

Please refer to BarmanObjectStoreConfiguration for a full list of options.

If required, you can choose to compress WAL files as soon as they are uploaded and/or encrypt them:

apiVersion: postgresql.k8s.enterprisedb.io/v1
kind: Cluster
[...]
spec:
  backup:
    barmanObjectStore:
      [...]
      wal:
        compression: gzip
        encryption: AES256

You can configure the encryption directly in your bucket, and the operator will use it unless you override it in the cluster configuration.

PostgreSQL implements a sequential archiving scheme, where the archive_command will be executed sequentially for every WAL segment to be archived.

Important

By default, EDB Postgres for Kubernetes sets archive_timeout to 5min, ensuring that WAL files, even in case of low workloads, are closed and archived at least every 5 minutes, providing a deterministic time-based value for your Recovery Point Objective (RPO). Even though you change the value of the archive_timeout setting in the PostgreSQL configuration, our experience suggests that the default value set by the operator is suitable for most use cases.

When the bandwidth between the PostgreSQL instance and the object store allows archiving more than one WAL file in parallel, you can use the parallel WAL archiving feature of the instance manager like in the following example:

apiVersion: postgresql.k8s.enterprisedb.io/v1
kind: Cluster
[...]
spec:
  backup:
    barmanObjectStore:
      [...]
      wal:
        compression: gzip
        maxParallel: 8
        encryption: AES256

In the previous example, the instance manager optimizes the WAL archiving process by archiving in parallel at most eight ready WALs, including the one requested by PostgreSQL.

When PostgreSQL will request the archiving of a WAL that has already been archived by the instance manager as an optimization, that archival request will be just dismissed with a positive status.

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