Using async for concurrent work

Introduction to FastAPI

Matt Eckerle

Software and Data Engineering Leader

Why use async? Concurrent Burgers!

Customers in line for burgers prepared and served in serial

Customers in line for burgers prepared and served concurrently

¹ https://fastapi.tiangolo.com/async/

Defining a function to get burgers

# This is not asynchronous
def get_sequential_burgers(number: int):
    # Do some sequential stuff
    return burgers

Calling the function sequentially

burgers = get_burgers(2)

Defining a function to get burgers

async def get_burgers(number: int):
    # Do some asynchronous stuff
    return burgers

Calling the function asynchronously

burgers = await get_burgers(2)

If we can:

results = await some_library()

Then use async def:

@app.get('/')
async def read_results():
    results = await some_library()
    return results

Note Only use await inside of functions created with async def

If our application needs to wait for other systems to respond

Examples

CPU-heavy tasks

Examples

If we aren't sure

Introduction to FastAPI