feat(storage): add async credential wrapper

[googlyrahman]

Adds async credential wrapper for async client.

Context:

• The standard google auth credentials are currently synchronous, and it's asynchronous credentials classes are either not available or marked private.
• Credential retrieval and refreshing will remain synchronous under the hood. Rationale: As authentication tokens typically possess an expiration lifetime of one hour, the blocking time required for token fetching occurs infrequently. The performance impact of blocking (or utilizing a separate thread for offloading) once per hour is deemed negligible when weighed against the considerable engineering cost of developing and maintaining a asynchronous authentication.

[gemini-code-assist]

Summary of Changes

Hello @googlyrahman, 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 a practical solution for integrating existing synchronous Google Auth credentials into asynchronous Python applications. By wrapping the synchronous credentials with an AsyncCredsWrapper, it enables asynchronous clients to utilize these credentials without blocking the event loop during infrequent operations like token refreshes. The approach balances the need for asynchronous compatibility with the engineering cost, focusing on efficiency for operations that are not performance-critical.

Highlights

• New Async Credential Wrapper: Introduces a new AsyncCredsWrapper class designed to adapt synchronous Google Auth credentials for use in asynchronous contexts.
• Asynchronous Interface for Synchronous Credentials: The wrapper provides async def refresh and async def before_request methods, allowing synchronous credential operations to be awaited without blocking the main event loop.
• Thread Pool for Blocking Operations: Blocking operations, such as token refreshes and initial credential application, are offloaded to a separate thread using asyncio.loop.run_in_executor.
• Performance Rationale: The design acknowledges that credential refreshing is infrequent (typically hourly), making the performance impact of offloading these blocking calls to a thread pool negligible compared to the complexity of a fully asynchronous authentication implementation.

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 introduces an AsyncCredsWrapper to adapt synchronous Google Auth credentials for asynchronous use. The approach of using run_in_executor for blocking calls is sound. My review includes a few suggestions to improve the implementation:

• The __init__ method should be updated to call super().__init__() and use the modern asyncio.get_running_loop() instead of the deprecated get_event_loop().
• The wrapper should delegate property access (e.g., valid, token) to the wrapped credentials object to ensure it behaves as a transparent proxy and provides correct state information.
• A minor simplification in the before_request method is also suggested.

These changes will make the wrapper more robust, correct, and easier to use.

[chandra-siri]

nit: sentence's meaning is not coming out clearly.