archive_library

archive_library sets the library that will be called to archive a WAL file. It is a sighup setting present in PG15–18; the latest recorded boot default is empty.

Note

Fact — official short description: “Sets the library that will be called to archive a WAL file.”

Identity

Type , Valuestring: Upstream pg_settings type
Context , Valuesighup: Takes effect after configuration reload
Unit , Value—: Raw unit
Range , Value—: Raw limits in the last observed version
Enum values , Value—: — for non-enum types
Category , ValueWrite-Ahead Log / Archiving: Upstream classification
Latest boot value , Value"": empty string

Lifecycle

Fact	Value
First observed	PG15
Present in	PG15–19 Beta 3
Removed in	No
Introduction commit	`5ef1eefd76f4` — Allow archiving via loadable modules.
Commit date	2022-02-03
Discussion	thread 1

Default history

Measured PG9.0–19 Beta 3 boot defaults
Versions	Raw `boot_val`	Unit	Human value
PG15–19 Beta 3	`""`	—	empty string

How it works

Sets the library that will be called to archive a WAL file. A configuration reload applies a new value; existing work already in flight is not retroactively changed.

A nonempty library selects an archive module through its _PG_archive_module_init callback instead of a shell command. archive_command and archive_library are alternative implementations; changing either is reloadable, while archive_mode must already be active.

Monitor and change archive_library together with archive_mode, archive_command, archive_timeout. Validate on the relevant server role and real workload, then use its sighup context to choose session change, reload, or restart; a historical boot default is not the current effective value.

Tuning advice

Tip

Advice. These are workload-specific starting points and must be validated with measurements.

Workload	Guidance
OLTP	Manage archive_library as part of the backup/restore protocol: the command or module must be idempotent, fail visibly, and be verified by restoring from the real archive—not merely by exit status.
OLAP	Provision archive throughput and capacity for bulk-load WAL peaks. If archiving falls behind, throttle the job and alert; never hide backlog with false success or aggressive cleanup.
Small nodes	Enable it only for a defined PITR requirement and use a mature backup tool. Keep rebuildable instances simple, but never install a no-op command that creates the illusion of a backup.

Pigsty

Values use the fixed 8-vCPU, 32-GiB, 100-GiB SSD fixture and render the current Pigsty templates for PG19 Beta 3; this does not assert current Pigsty support for that historical or beta release.

Template	Effective value	Versus upstream boot	Source expression
OLTP	Unmodified	—	—
OLAP	Unmodified	—	—
CRIT	Unmodified	—	—
TINY	Unmodified	—	—

Caution

Advice — pending human review. Fact from the current Pigsty template projection: OLTP: PG15–19 Beta 3 unmodified; OLAP: PG15–19 Beta 3 unmodified; CRIT: PG15–19 Beta 3 unmodified; TINY: PG15–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

Common pitfalls

Configuring both a library and expecting archive_command to run as a fallback.
Loading untrusted in-process archive code.
Treating module success as proof that restores work.
Reloading to a new module without verifying backlog processing, failure reporting, and rollback behavior.
Letting repeated module failures retain WAL until pg_wal fills, without an archive-lag alert.

archive_mode · archive_command · archive_timeout · archive_cleanup_command · restore_command · recovery_end_command