pre_auth_delay

pre_auth_delay — Sets the amount of time to wait before authentication on connection startup. Observed in PG9.0–19 Beta 3; its last measured boot default is 0 s in PG19 Beta 3, with sighup context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.

Note

Fact — official short description: “Sets the amount of time to wait before authentication on connection startup.”

Identity

Type , Valueinteger: Upstream pg_settings type
Context , Valuesighup: Takes effect after configuration reload
Unit , Values: Raw unit
Range , Value0 – 60: Raw limits in the last observed version
Enum values , Value—: — for non-enum types
Category , ValueDeveloper Options: Upstream classification
Latest boot value , Value0: 0 s

Lifecycle

Fact	Value
First observed	PG9.0 (research boundary)
Present in	PG9.0–19 Beta 3
Removed in	No
Introduction commit	Not asserted: predates the PG9.0 research boundary
Commit date	—
Discussion	—

Default history

Measured PG9.0–19 Beta 3 boot defaults
Versions	Raw `boot_val`	Unit	Human value
PG9.0–19 Beta 3	`0`	`s`	0 s

How it works

pre_auth_delay pauses a newly forked server process before authentication so a developer can attach a debugger to handshake and authentication code. Zero disables it.

The SIGHUP setting applies to future connection startups. While a process sleeps, the client is unauthenticated and a server process and connection slot can remain occupied.

It intentionally delays every affected connection and can amplify denial-of-service exposure. It is not a replacement for authentication_timeout or network rate limiting. Its SIGHUP context allows configuration reload without a server restart.

Tuning advice

Tip

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

Workload	Guidance
OLTP	Do not tune production OLTP with pre_auth_delay. Enable it only for a bounded reproduction with an owner, log/disk budget, rollback condition, and evidence-capture plan; restore the default immediately afterward.
OLAP	Long analytical runs can amplify pre_auth_delay’s debug overhead and artifacts. Prefer standard EXPLAIN and statistics first, and isolate any developer experiment from normal users.
Small nodes	Keep pre_auth_delay at its upstream default. A small host has less spare CPU, disk, connection, and log capacity for developer instrumentation.

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: PG9.0–19 Beta 3 unmodified; OLAP: PG9.0–19 Beta 3 unmodified; CRIT: PG9.0–19 Beta 3 unmodified; TINY: PG9.0–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

Common pitfalls

Leaving pre_auth_delay enabled after the bounded diagnostic or recovery task.
Running the experiment on the only copy of production data.
Underestimating log, core-file, temporary-file, WAL, CPU, or connection-slot amplification.
Treating a server that merely starts or completes a query as proof that data and behavior are correct.

post_auth_delay · authentication_timeout · max_connections · trace_connection_negotiation