Background Task in FastAPI Blocks Execution Despite Using BackgroundTasks

[Jay-fly]

Description:

When adding a background task to FastAPI’s BackgroundTasks, the execution of the task still blocks the main thread or API request. This issue persists even though the task is correctly added to BackgroundTasks.

Environment:

• FastAPI Version: 0.112.1
• FastAPI-Mail Version: 1.4.1
• Python Version: 3.10
• SMTP Server: Mailpit (running in Docker)
• Operating System: macOS Sequoia 15.0.1 (Apple M1)

Api Code

from fastapi import BackgroundTasks, FastAPI
from fastapi_mail import ConnectionConfig, FastMail, MessageSchema, MessageType

app = FastAPI()


@app.get("/send-mail")
async def send_mail(background_tasks: BackgroundTasks):
    message = MessageSchema(
        subject="Hello World",
        recipients=["test@test.com"],
        body="This is a test email",
        subtype=MessageType.plain,
    )

    conf = ConnectionConfig(
        MAIL_USERNAME="",
        MAIL_PASSWORD="",
        MAIL_PORT=1025,
        MAIL_SERVER="localhost",
        MAIL_STARTTLS=False,
        MAIL_SSL_TLS=False,
        MAIL_DEBUG=False,
        MAIL_FROM="noreply@test.com",
        USE_CREDENTIALS=False,
    )

    fm = FastMail(conf)

    # Adding to background task
    background_tasks.add_task(fm.send_message, message)
    return {"message": "Mail sent"}

this is a test api

@app.get("/test")
def test():

    return {"message": "Hello World"}

2024-12-17.6.07.31.mov