# logging_collector

> logging_collector is the PostgreSQL setting that controls whether PostgreSQL starts a subprocess to capture stderr, csvlog and/or jsonlog into log files.
---

> [!NOTE]
> **Fact — official short description:** “Start a subprocess to capture stderr, csvlog and/or jsonlog into log files.”

## Identity {#identity}

| Field | Value | Meaning |
| --- | --- | --- |
| Type | `bool` | Upstream pg_settings type |
| Context | `postmaster` | Requires a server restart |
| Unit | — | Raw unit |
| Range | — | Raw limits in the last observed version |
| Enum values | — | — for non-enum types |
| Category | Reporting and Logging / Where to Log | Upstream classification |
| Latest boot value | `off` | off |
{.fields meta="-"}

## Lifecycle {#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 {#default-history}

| Versions | Raw `boot_val` | Unit | Human value |
| --- | --- | --- | --- |
| PG9.0–19 Beta 3 | `off` | — | off |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

logging_collector starts a subprocess to capture stderr, csvlog and/or jsonlog into log files. The collector drains server stderr through a pipe and writes configured file formats; it is designed not to lose messages, so extreme backpressure can block emitters.

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

The active path is composed from log_destination, logging_collector or syslog/eventlog, file naming and permissions, rotation triggers, and external shipping or retention.

## Tuning advice {#tuning-advice}

> [!TIP]
> **Advice.** These are workload-specific starting points and must be validated with measurements.

| Workload | Guidance |
| --- | --- |
| OLTP | Enable logging_collector when csvlog/jsonlog or collector-managed stderr files are required, then load-test pipe throughput, rotation, disk-full behavior, shipping, and restart. It is a POSTMASTER setting and needs a controlled restart. |
| OLAP | Analytical workloads can emit large bursts at query completion; size collector and destination I/O for that burst and verify database processes do not stall behind collector backpressure. |
| Small nodes | Use one required format and bounded retention. A small node still needs disk alerts because the collector is designed not to lose messages and can propagate backpressure when its destination is slow or full. |
{.full-width}

## Pigsty {#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 | `on` | different | `'on'` |
| OLAP | `on` | different | `'on'` |
| CRIT | `on` | different | `'on'` |
| TINY | `on` | different | `'on'` |
{.full-width}

> [!CAUTION]
> **Advice — pending human review.** Fact from the current Pigsty template projection: OLTP: PG9.0–19 Beta 3 = on (dcs); OLAP: PG9.0–19 Beta 3 = on (dcs); CRIT: PG9.0–19 Beta 3 = on (dcs); TINY: PG9.0–19 Beta 3 = on (dcs). Advice, pending human review — Editorial inference: The collector is required for the configured csvlog file pipeline and gives all profiles managed local log files.

## Common pitfalls {#common-pitfalls}

- Expecting a reload or SET to activate logging_collector, although it requires a controlled server restart.
- Combining incompatible destination, collector, filename, and rotation assumptions and then losing or overwriting logs.
- Failing to monitor a full or unwritable log target, which can block logging or database activity depending on the path.
- Enabling file-oriented destinations without the collector, or starting the collector without a disk and retention plan.

## Related parameters {#related-parameters}

[`log_destination`](/parameters/log-destination/) · [`log_directory`](/parameters/log-directory/) · [`log_filename`](/parameters/log-filename/) · [`log_rotation_age`](/parameters/log-rotation-age/) · [`log_rotation_size`](/parameters/log-rotation-size/)

## References {#references}

- [PostgreSQL 19 Beta 3 — logging_collector](https://www.postgresql.org/docs/19/runtime-config-logging.html#GUC-LOGGING-COLLECTOR)
- [PostgreSQL 19 release notes](https://www.postgresql.org/docs/19/release-19.html)
- [Machine-readable GUC export](/data/guc.jsonl)