Document common function patterns and examples

[welteki]

Description

Document common function patterns and add examples for each pattern.

Motivation and Context

Provide a concise reference for common function patterns and demonstrate them with examples.

• I have raised an issue to propose this change (required)

How Has This Been Tested?

Verified the pages render correctly and the examples have been tested end-to-end.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have signed-off my commits with git commit -s

[alexellis]

Looks breaking.. same for Python?

[reviewfn]

AI Pull Request Overview

Disclaimer: This review was generated by automated AI and may contain errors. Do not trust its outputs without human verification.

Summary

• Adds a new Function patterns section covering director, async invocation, fan-out, fan-in, and singleton patterns.
• Adds language-specific example pages with Go, Python, and Node.js snippets.
• Updates language overview, Go page location, language example links, and MkDocs navigation.
• The new content is useful and mostly coherent, but a few examples have reproducibility issues.
• The Go director example contains an unused import that prevents a reader from building the copied code.
• The fan-in scaffolding commands appear to create the function in the wrong location relative to the existing fan-out stack.

Approval rating (1-10)

7/10. Useful documentation, but the build-breaking Go snippet and misleading fan-in setup steps should be fixed before merge.

Summary per file

Summary per file

File path	Summary
docs/languages/go/index.md	Renames Go page and links new pattern examples.
docs/languages/node.md	Adds links to director and fan-out examples.
docs/languages/overview.md	Updates Go link and introduces function patterns.
docs/languages/patterns/director.md	Adds director pattern tutorial and examples.
docs/languages/patterns/fan-in.md	Adds fan-in tutorial backed by PostgreSQL.
docs/languages/patterns/fan-out.md	Adds fan-out tutorial with worker callbacks.
docs/languages/patterns/index.md	Adds overview for common function patterns.
docs/languages/patterns/singleton.md	Adds singleton scaling tutorial and examples.
docs/languages/python/index.md	Adds links to pattern examples.
mkdocs.yml	Adds pattern navigation and Go page path.

Overall Assessment

The PR adds a substantial and relevant documentation section with a clear reader journey from overview to runnable examples. The main merge risks are not architectural; they are reproducibility defects in copied commands and code snippets. Fixing those should make the new section publishable.

Detailed Review

Detailed Review

Content review

Findings

Medium: Go director example will not compile because context is unused

In docs/languages/patterns/director.md:91-104, the function-a/handler.go snippet imports context but never references it:

import (
    "context"
    "encoding/json"
    "net/http"
)

Go rejects unused imports, so a reader copying this example into the generated golang-middleware function will hit a build failure before they can run the director workflow. Remove the context import from the function-a snippet.

Medium: Fan-in scaffolding commands create the function outside the expected stack layout

In docs/languages/patterns/fan-in.md:51-79, the page says the reader is extending the Fan-out example, then instructs them to run mkdir fan-in && cd fan-in followed by faas-cli new ... fan-in. That creates a nested fan-in/fan-in function project and a separate stack.yaml instead of appending fan-in to the existing stack that already contains fan-out and batch-worker. Later, docs/languages/patterns/fan-in.md:631-635 tells the reader to deploy fan-in after completing the Fan-out example with faas-cli up --tag=sha, but the original fan-out stack will not include this new function.

Make the setup match the rest of the workflow by scaffolding from the existing fan-out project root and appending to the current stack.yaml, for example:

faas-cli template store pull golang-middleware
faas-cli new --lang golang-middleware fan-in \
  --append stack.yaml --prefix ttl.sh/openfaas-examples

Apply the same structure to the Python and Node.js tabs so the paths like fan-in/handler.go, the fan-in/schema.sql path, and the final faas-cli up --tag=sha command all refer to the same project layout.

Low: Director page uses an undefined Markdown reference link for ttl.sh

In docs/languages/patterns/director.md:74-75, the text uses [ttl.sh] without an inline URL or reference definition. The other pattern pages use [ttl.sh](https://ttl.sh), so this page will render inconsistently and readers lose the registry link. Change it to:

The example uses the public [ttl.sh](https://ttl.sh) registry.

Additional content observations

The overview page gives a clear entry point into the new pattern section, and the new navigation in mkdocs.yml makes the pages discoverable.

The pattern pages have consistent structure: problem framing, scaffolding, implementation, configuration, deployment, and considerations. That makes the section easy to scan across languages.

The content does not use front matter titles or excerpts, so title/excerpt fit is not applicable in the changed pages. The page headings and navigation labels are aligned with the article scope.

AI agent details.

Agent processing time: 1m36.038s
Environment preparation time: 3.453s
Total time from webhook: 1m44.433s