Fastapi on Rainux

Executing Asynchronous Scheduled Tasks with Database-Based Distributed Locking in FastAPI

Sun, 08 Feb 2026 23:56:57 +0800

This article provides a comprehensive guide on implementing an asynchronous task scheduler in FastAPI, using database-based distributed locks to prevent duplicate task execution in multi-process environments.

FastAPI - Calling Synchronous Methods in FastAPI Asynchronous Methods

Tue, 06 Jan 2026 16:19:44 +0800

Introduction

Directly calling synchronous methods within asynchronous methods blocks the entire event loop, preventing the application from handling any other concurrent requests while executing the synchronous method. This severely impacts the overall performance and responsiveness of the service.

To address this issue, the core approach is to delegate synchronous methods to external thread pools or process pools for execution, thereby avoiding blocking the main event loop.

Method 1: Using asyncio.to_thread

Python 3.9 and later versions provide the asyncio.to_thread method, which runs synchronous functions in a separate thread and returns a coroutine object that can be awaited.

FastAPI - Design of tracking_id

Thu, 11 Dec 2025 00:40:44 +0800

Introduction

In real business scenarios, tracing a request’s complete processing path in logs based on a tracking_id is a common requirement. However, FastAPI does not provide this functionality out of the box, so developers need to implement it themselves. This article introduces how to add a tracking_id to the entire request lifecycle based on contextvars and automatically record it in logs.

What is contextvars

Python 3.7 added a module contextvars to the standard library, which stands for “Context Variables”. It is typically used to implicitly pass some environmental information variables, similar to threading.local(). However, threading.local() is thread-specific, isolating data states between threads, while contextvars can be used in asynchronous coroutines within the asyncio ecosystem. PS: contextvars can not only be used in asynchronous coroutines but can also replace threading.local() in multi-threaded functions.