Resolving async Issues in Aiohttp ClientSession for FastAPI Testing

Learn how to effectively utilize Aiohttp in your FastAPI tests by addressing common `async` issues and optimizing request times for multiple API tests.
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Troubleshooting Async Issues in Aiohttp ClientSession for FastAPI Testing

When you're working with FastAPI and Aiohttp, testing your asynchronous code can sometimes become challenging. Many developers encounter issues like the async keyword not functioning as expected or experiencing lengthy response times when making multiple requests. In this guide, we'll explore a specific case and provide a solution to help streamline your testing process.

Understanding the Challenge

In various scenarios involving FastAPI and Aiohttp, developers might face two common problems:

Async Doesn't Work: The code fails to run concurrently as expected, causing each request to execute sequentially instead of simultaneously.

Response Time is Too Long: When making numerous requests (for example, 50 or more), the time taken for responses is significantly longer than anticipated.

The Context

To illustrate this, consider a FastAPI application where an API is set up to create city objects in a PostgreSQL database using SQLAlchemy. Developers might want to send requests using a JSON file containing multiple city entries and validate the API's performance under load.

Analyzing the Code

Here is a simplified version of the code structure where the above problems occur:

FastAPI Endpoint

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This portion creates a city object based on the incoming data.

Aiohttp Request Function

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Main Driver Function

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Here, developers attempt to send multiple requests to the API. However, the structure leads to sequential execution rather than concurrent processing.

Proposed Solutions

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2. Adjust the Timing of Your Print Statement

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This will ensure you track the entire duration of the request, providing better analytics for performance assessment.

Conclusion

By implementing these changes, you should be able to enhance the performance of your FastAPI testing using Aiohttp. The adjustments will help you leverage the full power of asynchronous programming, allowing your tests to run multiple requests concurrently while keeping response times manageable.

For your next testing phase, remember to ensure your code is structured for concurrency. This simple optimization can save you significant time and trouble when testing APIs under load.

Happy coding!