ssl_prefer_server_ciphers

ssl_prefer_server_ciphers is the PostgreSQL setting that gives priority to server ciphersuite order.

Note

Fact — official short description: “Give priority to server ciphersuite order.”

Identity

Type , Valuebool: 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 , ValueConnections and Authentication / SSL: Upstream classification
Latest boot value , Valueon: on

Lifecycle

Fact	Value
First observed	PG9.4
Present in	PG9.4–19 Beta 3
Removed in	No
Introduction commit	`ef3267523d1e` — SSL: Add configuration option to prefer server cipher order
Commit date	2013-12-07
Discussion	—

Default history

Measured PG9.0–19 Beta 3 boot defaults
Versions	Raw `boot_val`	Unit	Human value
PG9.4–19 Beta 3	`on`	—	on

How it works

ssl_prefer_server_ciphers gives priority to server ciphersuite order. It affects server-versus-client ordering only for TLS 1.2 and older; TLS 1.3 negotiation does not use this switch.

ssl_prefer_server_ciphers is a SIGHUP-context setting: a configuration reload activates the new server value without a restart; subsequent operations that consult it use the refreshed value. Existing TLS sessions are not renegotiated.

It participates in the TLS context used for new handshakes. ssl enables transport, pg_hba.conf decides which connection classes require it, and the certificate, key, CA, revocation, protocol, and cipher settings must form one valid policy.

Tuning advice

Tip

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

Workload	Guidance
OLTP	Treat ssl_prefer_server_ciphers as transport-security policy rather than a performance knob. Follow the organization’s TLS baseline and test certificate rotation, reload, and every client class.
OLAP	Use the same TLS floor for analytical traffic; benchmark only after correctness because bulk transfer may expose CPU cost but is not a reason to accept obsolete protocols.
Small nodes	Keep ssl_prefer_server_ciphers simple and secure, using managed certificates and library defaults reviewed for the installed OpenSSL version. Rehearse renewal before expiry.

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: PG9.4–19 Beta 3 unmodified; OLAP: PG9.4–19 Beta 3 unmodified; CRIT: PG9.4–19 Beta 3 unmodified; TINY: PG9.4–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

Common pitfalls

Editing ssl_prefer_server_ciphers without reloading configuration and verifying the effective value and subsequent behavior.
Updating only one TLS file or policy knob and leaving an invalid chain, unreadable key, or incompatible protocol set.
Assuming a reload renegotiates existing sessions; TLS policy changes affect new handshakes.
Assuming it controls TLS 1.3 cipher ordering.

ssl_ciphers · ssl_tls13_ciphers · ssl_min_protocol_version · ssl_max_protocol_version · ssl_groups