In modern web applications, high performance and fast responsiveness are crucial. Python's FastAPI framework has become the preferred choice for many developers due to its outstanding performance and user-friendly features.
In Python, a thread is a separate flow of execution that can run concurrently with other threads. Each thread operates independently, and multiple threads can be created and executed within a single program. This is in contrast to the traditional sequential execution, where tasks are executed one after the other.
In certain scenarios, single-threaded execution may not meet the requirements, prompting the consideration of using multi-threading to enhance application concurrency. This article will explore the usage of multi-threading in the FastAPI framework, covering common use cases, problem-solving approaches, and practical examples.
One of the main benefits of multi-threading is improved performance. By dividing a task into multiple threads, each responsible for a specific subtask, the overall execution time can be reduced. This is particularly useful in FastAPI applications, where tasks such as handling requests, processing data, and performing computations can be parallelized.
To understand multi-threading in Python, it's essential to grasp some key concepts. First, Python's Global Interpreter Lock (GIL) restricts the execution of multiple threads simultaneously in the same process. This means that even though multiple threads are created, only one thread can execute Python bytecode at a time. As a result, multi-threading in Python does not provide true parallelism but rather concurrent execution.
However, multi-threading can still offer performance improvements in FastAPI applications. While the GIL prevents multiple threads from executing Python code simultaneously, it does not restrict other operations, such as I/O operations, network requests, or database queries. By offloading these operations to separate threads, the main thread can focus on other tasks, effectively utilizing the available resources and improving overall performance.
In FastAPI, implementing multi-threading involves creating and managing threads to perform specific tasks concurrently. This can be achieved using the threading module in Python, which provides a high-level interface for creating and managing threads. By creating and starting multiple threads, developers can distribute the workload across different threads and improve the application's responsiveness.
You can directly create threads using the threading module within path operation functions.
import threading
from fastapi import FastAPI
app = FastAPI()
@app.get("/resource")
def get_resource():
t = threading.Thread(target=do_work)
t.start()
return {"message": "Thread started"}
def do_work():
# perform computationally intensive work here
FastAPI provides the @app.on_event("startup") decorator to create background tasks during startup.
from fastapi import FastAPI, BackgroundTasks
app = FastAPI()
@app.on_event("startup")
def startup_event():
threading.Thread(target=do_work, daemon=True).start()
def do_work():
while True:
# perform background work
You can employ third-party libraries like apscheduler to execute periodic background tasks.
from apscheduler.schedulers.background import BackgroundScheduler
from fastapi import FastAPI
app = FastAPI()
scheduler = BackgroundScheduler()
@app.on_event("startup")
def start_background_processes():
scheduler.add_job(do_work, "interval", seconds=5)
scheduler.start()
def do_work():
# perform periodic work
Installing Required Tools
First, ensure that you have Python and pip installed. Then, use the following command to install FastAPI and uvicorn:
pip install fastapi
pip install uvicorn
Writing a Multi-threaded Application
Let's create a simple FastAPI application:
from fastapi import FastAPI
import threading
import time
app = FastAPI()
# Time-consuming task function
def long_running_task(task_id: int):
print(f"Starting Task {task_id}")
time.sleep(5) # Simulate task execution time
print(f"Finished Task {task_id}")
# Background task function
def run_background_task(task_id: int):
thread = threading.Thread(target=long_running_task, args=(task_id,))
thread.start()
@app.get("/")
async def read_root():
return {"Hello": "World"}
@app.get("/task/{task_id}")
async def run_task_in_background(task_id: int):
# Create and start a background thread to run the task
run_background_task(task_id)
return {"message": f"Task {task_id} is running in the background."}
if __name__ == "__main__":
import uvicorn
uvicorn.run(app, host="127.0.0.1", port=8000)
In this example, we use the threading.Thread class to create a background thread for running the time-consuming task. Inside the run_background_task function, we create a thread object thread with long_running_task as its target function, passing task_id as an argument. Then, we call thread.start() to launch a new thread and run long_running_task in the background.
Running the Application
Use the following command to run the FastAPI application:
uvicorn main:app --reload
Now, you can test the application using a browser or a tool like curl. For instance, open a browser, type http://localhost:8000/task/1, and hit Enter. You will immediately receive the response {"message": "Task 1 is running in the background."}, and the task running in the background will print "Finished Task 1" after 5 seconds. Meanwhile, you can continue sending other task requests.
Apidog is an all-in-one API collaboration platform that integrates API documentation, API debugging, API mocking, and API automation testing. With Apidog, we can easily debug FastAPI interfaces.
To quickly debug an API endpoint, create a new project and select the "Debug Mode." Fill in the request address, and you can swiftly send the request to obtain the response results, as illustrated in the example above.
Multi-threading can be a powerful tool for optimizing code execution, but it also comes with its own set of challenges and considerations.
concurrent.futures.ThreadPoolExecutor to gracefully shut down threads when they are no longer needed.
