event_source

event_source is the PostgreSQL setting that defines the application name used to identify PostgreSQL messages in the event log.

Note

Fact — official short description: “Sets the application name used to identify PostgreSQL messages in the event log.”

Identity

Type , Valuestring: Upstream pg_settings type
Context , Valuepostmaster: Requires a server restart
Unit , Value—: Raw unit
Range , Value—: Raw limits in the last observed version
Enum values , Value—: — for non-enum types
Category , ValueReporting and Logging / Where to Log: Upstream classification
Latest boot value , ValuePostgreSQL: PostgreSQL

Lifecycle

Fact	Value
First observed	PG9.2
Present in	PG9.2–19 Beta 3
Removed in	No
Introduction commit	`d8ea33f2c027` — Support configurable eventlog application names on Windows
Commit date	2011-10-25
Discussion	—

Default history

Measured PG9.0–19 Beta 3 boot defaults
Versions	Raw `boot_val`	Unit	Human value
PG9.2–19 Beta 3	`PostgreSQL`	—	PostgreSQL

How it works

event_source sets the application name used to identify PostgreSQL messages in the event log. This is a Windows event-log identifier and has no effect unless eventlog is an active log destination.

event_source is a POSTMASTER-context setting: PostgreSQL reads it during server startup, and a configuration reload or session SET cannot activate a new value.

event_source is consulted only on Windows when eventlog is selected in log_destination; Windows Event Log registration, permissions, routing, and retention supply the rest of the pipeline.

Tuning advice

Tip

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

Workload	Guidance
OLTP	Set event_source only for a Windows eventlog deployment, using a stable non-secret identity registered and routed by the host logging policy.
OLAP	Keep the same event source across workload classes so Windows collection rules and dashboards do not fragment by profile.
Small nodes	Leave event_source at its default unless eventlog is selected; changing a dormant label provides no capacity or observability benefit.

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: PG9.2–19 Beta 3 unmodified; OLAP: PG9.2–19 Beta 3 unmodified; CRIT: PG9.2–19 Beta 3 unmodified; TINY: PG9.2–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

Common pitfalls

Expecting a reload or SET to activate event_source, although it requires a controlled server restart.
Changing the source name without registering or updating Windows Event Log routing and access policy.
Expecting event_source to have any effect when eventlog is not an active log destination or the platform is not Windows.
Changing event_source globally without a rollback plan and a client or operational compatibility test.

logging_collector · log_destination · log_directory · log_filename · log_rotation_age · log_rotation_size