[beeme1mr]

This PR

• adds observability hook guidelines to the appendix

Notes

This is based on the updated telemetry hook @lukas-reining wrote. I tried to capture as much context as possible so that other maintainers can understand how the hook should be written.

Since this is in the appendix section, I decided to make the guide human-readable instead of just a list of requirements.

Follow-up Tasks

Create implementation issues for all SDKs based on these guidelines.

[gemini-code-assist]

Summary of Changes

Hello @beeme1mr, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces comprehensive guidelines for implementing observability hooks that emit OpenTelemetry signals during feature flag evaluations. The new guide, added to the specification's appendix, aims to standardize how maintainers write telemetry hooks across various SDKs by detailing signal emission patterns, hook lifecycle responsibilities, attribute transformations, and privacy considerations for flag values. This will facilitate consistent and robust telemetry integration.

Highlights

• New Telemetry Hook Implementation Guide: A comprehensive guide has been added to the observability appendix, detailing how to implement telemetry hooks for feature flag evaluations.
• Signal Emission Patterns: The guide outlines three distinct patterns for emitting OpenTelemetry signals: Span Events (recommended), Event Logging, and Standalone Spans, along with their advantages and disadvantages.
• Hook Lifecycle and Error Handling: Detailed instructions are provided for implementing the before, finally, and error stages of a hook, emphasizing graceful error handling that does not interrupt flag evaluation.
• Attribute Transformation and Privacy: Guidelines are included for transforming flag metadata into OpenTelemetry attributes and for handling sensitive flag values, with recommendations for redaction and configurable privacy options.
• Standardized Configuration and Patterns: Common configuration options and implementation patterns, such as a base class for shared functionality, are suggested to ensure consistency across SDK implementations.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request adds a comprehensive and well-structured guide for implementing telemetry hooks. The documentation covers important aspects like signal emission patterns, hook lifecycle, attribute transformations, privacy, configuration, and error handling. I've added a couple of suggestions to improve the clarity and precision of the guidelines, which is important for a specification document. Overall, this is a valuable addition.

[erka]

@beeme1mr Please clarify what the span event name should be - feature_flag.evaluation?

[beeme1mr]

@beeme1mr Please clarify what the span event name should be - feature_flag.evaluation?

@erka done!

[askpt]

LGTM! Just two minor questions in case they're typos.

[beeme1mr]

I'll merge tomorrow (Nov 5th) unless someone objects.