# io_worker_launch_interval

> io_worker_launch_interval — Minimum time before launching a new I/O worker process, for io_method=worker. Observed in PG19 Beta 3; its last measured boot default is 100 ms 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:** “Minimum time before launching a new I/O worker process, for io_method=worker.”

## Identity {#identity}

| Field | Value | Meaning |
| --- | --- | --- |
| Type | `integer` | Upstream pg_settings type |
| Context | `sighup` | Takes effect after configuration reload |
| Unit | `ms` | Raw unit |
| Range | `0` – `2147483647` | Raw limits in the last observed version |
| Enum values | — | — for non-enum types |
| Category | Resource Usage / I/O | Upstream classification |
| Latest boot value | `100` | 100 ms |
{.fields meta="-"}

## Lifecycle {#lifecycle}

| Fact | Value |
| --- | --- |
| First observed | PG19 Beta 3 |
| Present in | PG19 Beta 3 |
| Removed in | No |
| Introduction commit | [`d1c01b79d4ae`](https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=d1c01b79d4ae90e52bf9db9c05c9de17b7313e85) — aio: Adjust I/O worker pool automatically. |
| Commit date | 2026-04-08 |
| Discussion | [thread 1](https://postgr.es/m/CA%2BhUKG%2Bm4xV0LMoH2c%3DoRAdEXuCnh%2BtGBTWa7uFeFMGgTLAw%2BQ%40mail.gmail.com) |

## Default history {#default-history}

| Versions | Raw `boot_val` | Unit | Human value |
| --- | --- | --- | --- |
| PG19 Beta 3 | `100` | `ms` | 100 ms |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

PostgreSQL describes io_worker_launch_interval as follows: “Minimum time before launching a new I/O worker process, for io_method=worker.” A configuration reload applies the value to the server without a full restart. The atlas measures it in PG19 Beta 3; boot_val is the compiled or initialized baseline, not proof of a running cluster's effective setting.

These controls govern the elastic background-worker pool used only when io_method is worker. io_min_workers keeps warm capacity, io_max_workers caps the pool, io_worker_launch_interval damps short bursts, and io_worker_idle_timeout lets unused workers retire; they do not raise a backend's separate io_max_concurrency ceiling.

Read it together with io_min_workers, io_max_workers, io_worker_idle_timeout, io_method. Check SHOW and pg_settings on the target server, verify the source and pending_restart fields, and compare workload, logs, and resource metrics before and after any change.

## Tuning advice {#tuning-advice}

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

| Workload | Guidance |
| --- | --- |
| OLTP | Benchmark with the production storage stack and concurrency. Optimize tail latency and queue depth, not only average throughput, and retain capacity for WAL, checkpoints, and foreground reads. |
| OLAP | Use representative scans, prefetch, and spill phases. Increase concurrency or worker capacity only while throughput rises without unacceptable CPU overhead, memory pressure, or storage saturation. |
| Small nodes | Prefer auto or the upstream worker limits. Validate with pg_test_timing or I/O statistics as applicable; a larger pool on a small node can add context switching without useful parallelism. |
{.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 | Unmodified | — | — |
| OLAP | Unmodified | — | — |
| CRIT | Unmodified | — | — |
| TINY | Unmodified | — | — |
{.full-width}

> [!CAUTION]
> **Advice — pending human review.** Fact from the current Pigsty template projection: OLTP: PG19 Beta 3 unmodified; OLAP: PG19 Beta 3 unmodified; CRIT: PG19 Beta 3 unmodified; TINY: PG19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

## Common pitfalls {#common-pitfalls}

- Treating the measured boot_val for io_worker_launch_interval as proof of the effective value on an initialized or managed cluster.
- Applying a change as though it were immediate while pg_settings reports sighup context.
- Changing this setting in isolation without checking the linked limits, observability, and rollback path.
- Depending on beta behavior in production without retesting the PostgreSQL 19 final release.

## Related parameters {#related-parameters}

[`io_min_workers`](/parameters/io-min-workers/) · [`io_max_workers`](/parameters/io-max-workers/) · [`io_worker_idle_timeout`](/parameters/io-worker-idle-timeout/) · [`io_method`](/parameters/io-method/) · [`io_max_concurrency`](/parameters/io-max-concurrency/) · [`io_combine_limit`](/parameters/io-combine-limit/)

## References {#references}

- [PostgreSQL 19 Beta 3 — io_worker_launch_interval](https://www.postgresql.org/docs/19/runtime-config-resource.html#GUC-IO-WORKER-LAUNCH-INTERVAL)
- [PostgreSQL 19 release notes](https://www.postgresql.org/docs/19/release-19.html)
- [Machine-readable GUC export](/data/guc.jsonl)