change to prefork, with ADR note in docs

[pooleycodes]

What type of PR is this? (check all applicable)

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update

Description

Async tasks were never being killed, an investigation revealed this was due to eventlet being used, this has been changed to prefork with ADR note in docs here for this.

Related Tickets & Documents

• Ticket Link Is Celery timeout limit actually being used? #128
• Related Issue #
• Closes #

QA Instructions, Screenshots, Recordings

Tested in local with SIGKILL working and tested in Dev.

Added/updated tests?

We encourage you to keep the code coverage percentage at 80% and above. Please refer to the Digital Land Testing Guidance for more information.

• Yes
• No, and this is why: Infrastructure change not logic change, tested in Dev.
• I need help with writing tests

[optional] Are there any post deployment tasks we need to perform?

No

[optional] Are there any dependencies on other PRs or Work?

No

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Review details

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: c2372801-8fef-4828-ac92-773233eb1f01

📥 Commits

Reviewing files that changed from the base of the PR and between 6ac1b56 and 29ec5cd.

📒 Files selected for processing (2)

• docs/celery-worker-pool.md
• request-processor/docker-entrypoint.sh

Walkthrough

The Celery request-processor worker now runs with the prefork pool instead of eventlet. An ADR documents the decision, explicit concurrency configuration, operational consequences, and future ECS scaling options.

Changes

Celery prefork worker pool

Layer / File(s)	Summary
Prefork decision and worker wiring docs/celery-worker-pool.md, request-processor/docker-entrypoint.sh	The worker command switches to -P prefork while retaining CELERY_WORKER_CONCURRENCY with a default of 1; the ADR documents the execution model, resource implications, and scaling roadmap.

Estimated code review effort: 1 (Trivial) | ~5 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarises the main change: switching Celery to prefork and adding an ADR note in the docs.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch 128-is-celery-timeout-limit-actually-being-used

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Actionable comments posted: 3

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@docs/celery-worker-pool.md`:
- Around line 53-54: Update the concurrency statement in the Celery worker pool
documentation to avoid claiming there is no behavioral change; state only that
configured task concurrency remains 1, while preserving the existing note about
deliberately increasing it via the roadmap.
- Around line 22-27: Revise the Eventlet caveat in the workload discussion to
state that psycopg2 may cooperate when Eventlet greening is enabled, while this
workload’s transforms and database writes may still limit parallelism; avoid
presenting GIL or blocking C-call serialization as inherent. Also qualify any
claim that the 30-minute task_time_limit never fired, tying it to the deployed
Celery/Eventlet version or verified blocking-task evidence.

In `@request-processor/docker-entrypoint.sh`:
- Line 4: Quote the CELERY_WORKER_CONCURRENCY expansion in the Celery worker
command, using the default value of 1 while preserving it as a single argument
to --concurrency.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 4fa9e842-98d3-48df-b5a8-1fe8298bb68a

📥 Commits

Reviewing files that changed from the base of the PR and between 1da8fa6 and 6ac1b56.

📒 Files selected for processing (2)

• docs/celery-worker-pool.md
• request-processor/docker-entrypoint.sh

[gibahjoe]

LGTM