feat(nginx): add NGINX_WORKER_PROCESSES env var

[fzipi]

Summary

• Adds an NGINX_WORKER_PROCESSES environment variable to control nginx's worker_processes directive (previously hardcoded to auto)
• Default stays auto, so behavior is unchanged unless the variable is set explicitly

Why

worker_processes was hardcoded to auto, which spreads nginx's buffered log writes across multiple worker processes. When several workers race to flush, log lines can land out of order, which breaks consumers that rely on log markers to bound a single request's output (e.g. go-ftw's marker-based test runner, coreruleset/go-ftw#473).

Reapplies the change reverted in #455, this time through normal PR review.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Added support for configuring the number of NGINX worker processes through the NGINX_WORKER_PROCESSES environment variable.
  • The setting defaults to auto, while allowing a fixed value when needed.
  • Configuration is applied consistently across standard and Alpine-based images.

• Documentation

  • Documented the new environment variable, including its default and configuration example.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: Organization UI

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Run ID: 42d00b88-10a1-48ee-94a0-8bb6d976a3db

📥 Commits

Reviewing files that changed from the base of the PR and between d057864 and 605ad5b.

📒 Files selected for processing (1)

• README.md

🚧 Files skipped from review as they are similar to previous changes (1)

• README.md

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📝 Walkthrough

Walkthrough

The Docker images now define NGINX_WORKER_PROCESSES=auto. The NGINX template uses this variable for the worker_processes directive. The README documents the variable and its effect on log writes.

Changes

NGINX worker process configuration

Layer / File(s)	Summary
Worker process configuration nginx/Dockerfile, nginx/Dockerfile-alpine, nginx/templates/nginx.conf.template, README.md	Both Dockerfiles set NGINX_WORKER_PROCESSES=auto. The NGINX template references the variable in the worker_processes directive. The README documents the variable and its fixed-value behavior.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Possibly related PRs

• coreruleset/modsecurity-crs-docker#455: Modifies the same NGINX_WORKER_PROCESSES configuration and related documentation.

Suggested reviewers: theseion

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the addition of the NGINX_WORKER_PROCESSES environment variable.
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.

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[coderabbitai]

Actionable comments posted: 1

🤖 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 `@README.md`:
- Line 261: Update the NGINX_WORKER_PROCESSES documentation to state that
setting it to exactly 1 serializes log writes; remove the implication that any
fixed number provides this behavior, while retaining the default value and
directive reference.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

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

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 4149b45d-fd45-4676-a175-934ce16dfa1f

📥 Commits

Reviewing files that changed from the base of the PR and between c0ee516 and d057864.

📒 Files selected for processing (4)

• README.md
• nginx/Dockerfile
• nginx/Dockerfile-alpine
• nginx/templates/nginx.conf.template

[Copilot]

Pull request overview

This PR reintroduces configurability for nginx’s worker_processes by exposing it as an environment variable, enabling users (and test harnesses) to force single-worker operation to avoid out-of-order log lines.

Changes:

• Add NGINX_WORKER_PROCESSES to control the worker_processes directive (default remains auto).
• Update nginx config template to use the new environment-driven value.
• Document the new environment variable in the README and set defaults in both nginx Dockerfiles.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
README.md	Documents NGINX_WORKER_PROCESSES and its intended use for serializing log output.
nginx/templates/nginx.conf.template	Replaces hardcoded worker_processes auto; with ${NGINX_WORKER_PROCESSES}.
nginx/Dockerfile-alpine	Sets default NGINX_WORKER_PROCESSES=auto for the alpine nginx image variant.
nginx/Dockerfile	Sets default NGINX_WORKER_PROCESSES=auto for the debian-based nginx image variant.

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