Asyncio example is completely wrong, update

[agronick]

Issue Summary

I'm talking about this example https://github.com./sendgrid/sendgrid-python/blob/main/use_cases/asynchronous_mail_send.md

Steps to Reproduce

Using asyncio is more than just putting async in front of the function doing the http request. In fact this is the completely wrong way to use asyncio and will actually destroys performance as this blocks the event loop from doing any other work while the http request is being made.

To use asyncio correctly the tcp socket sending the data must be using asyncio and one of the low level asyncio socket functions. https://docs.python.org/3/library/asyncio-stream.html These are awaited, allowing the event loop to do other work.

What you have suggested is EXTREMELY bad practice and will stall the servers of anyone who uses it. This is why you can't use requests or urllib with asyncio. You have to use something like aiohttp.

The right way to use asyncio with your library is to run it in a thread pool executor so that the blocking IO stays off the main thread.

You would be better off deleting that example than keeping it in it's current form.

[thinkingserious]

Hello @agronick,

Thank you for raising this issue!

This issue has been added to our internal backlog to be prioritized. Pull requests and +1s on the issue summary will help it move up the backlog.

Here are some related issues and PRs to consider upon update:

• IMPROVEMENT: Support for asynchronous sending #296
• Add support for Proxies #409
• Asynchronous Mail Send example added to USE_CASES.md #363
• docs: fix asynchronous_mail_send #953

With best regards,

Elmer

[agronick]

#953 is exactly what I'm talking about but it was closed.

[parikls]

upvote. unfortunately current SDK is not compatible with asyncio which makes it unusable with such things like aiohttp or fastapi

[dacevedo12]

Hi, it's 2024 and the example is still wrong. Open to PRs? I can help

It's as simple as wrapping the call using asyncio.to_thread so it doesn't block the main thread.

Ideally though the SDK itself would provide support for asyncio, maybe through a transport layer that uses aiohttp or httpx

[urbanonymous]

I'll just use the api lol

[RobertoPrevato]

@agronick is right. The async example is wrong and misleading for less experienced developers. And I agree with @urbanonymous that it's best using the API directly.
I prepared an example of SendGrid client that sends async emails using httpx:

# example.py

from abc import ABC, abstractmethod
from dataclasses import dataclass


# TODO: use Pydantic for the Email object.
@dataclass
class Email:
    recipients: list[str]
    sender: str
    sender_name: str
    subject: str
    body: str
    cc: list[str] = None
    bcc: list[str] = None


class EmailHandler(ABC):  # interface
    @abstractmethod
    async def send(self, email: Email) -> None:
        pass


# ----------------------------------------------
# SendGrid implementation of EmailHandler
# ----------------------------------------------
import httpx


class SendGridClient(EmailHandler):
    def __init__(self, api_key: str, http_client: httpx.AsyncClient):
        if not api_key:
            raise ValueError("API key is required")
        self.http_client = http_client
        self.api_key = api_key

    async def send(self, email: Email) -> None:
        response = await self.http_client.post(
            "https://api.sendgrid.com/v3/mail/send",
            headers={
                "Authorization": f"Bearer {self.api_key}",
                "Content-Type": "application/json",
            },
            json=self.get_body(email),
        )
        # Note: in case of error, inspect response.text
        response.raise_for_status()  # Raise an error for bad responses

    def get_body(self, email: Email) -> dict:
        return {
            "personalizations": [
                {
                    "to": [{"email": recipient} for recipient in email.recipients],
                    "subject": email.subject,
                    "cc": [{"email": cc} for cc in email.cc] if email.cc else None,
                    "bcc": [{"email": bcc} for bcc in email.bcc] if email.bcc else None,
                }
            ],
            "from": {"email": email.sender, "name": email.sender_name},
            "content": [{"type": "text/html", "value": email.body}],
        }

# ----------------------------------------------
# Test
# ----------------------------------------------
import os

async def example():

    async with httpx.AsyncClient() as http_client:
        sendgrid = SendGridClient(
            api_key=os.environ.get("SENDGRID_API_KEY"), http_client=http_client
        )

        await sendgrid.send(
            Email(
                recipients=["[email protected]"],
                sender="[email protected]",
                sender_name="Example",
                subject="Test email",
                body="<h1>Hello</h1>",
            )
        )


if __name__ == "__main__":
    import asyncio

    asyncio.run(example())

PowerShell:

$env:SENDGRID_API_KEY="<YOUR_API_KEY>"

python example.py

Bash:

SENDGRID_API_KEY="<YOUR_API_KEY>" python example.py

Tip

Do not instantiate a new AsyncClient every time you want to use it, reuse one in your application lifetime.
If in doubt, read about TCP connection pooling. https://www.python-httpx.org/advanced/clients/#why-use-a-client

Tip

To understand why the example in this repository is wrong, watch this: Ryan Dahl: Original Node.js presentation.