client.connect() call hangs after server timeout about aiosmtplib HOT 8 OPEN

client.is_connected should always be a boolean, and client.connect() shouldn't hang. Any idea what it's hanging on?

You can avoid the whole problem by using the send coroutine and creating a new connection each time, which is probably better practice anyway. But if you do have any more information, please provide it 🙂

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I'm not sure why client was hanging, that may have something to do with the SMTP server we use, which I have no info about. For now I fixed it by creating a new client each time, which seems to work 🤔

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Could you explain why creating a new connection would be considered best practice by the way?

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It's just a simple way to avoid a lot of error states from server timeouts, etc.

I wonder if there is an internal lock in the library that's getting stuck, I'll see if I can add some test cases around that.

from aiosmtplib.

I tried writing a context manager like this:

@contextlib.asynccontextmanager
async def reconnect_smtp_client(
    client: aiosmtplib.SMTP,
    timeout: float = 15,
) -> AsyncIterator[None]:
    try:
        if not client.is_connected:
            logging.warning("SMTP client is not connected, reconnecting.")
            async with asyncio.timeout(timeout):
                await client.connect()
        yield
    except SMTPServerDisconnected:
        logging.warning("Caught SMTPServerDisconnected exception, reconnecting.")
        async with asyncio.timeout(timeout):
            await client.connect()
        raise

But as I said it hanged on client.connect() indefinitely (initially asyncio.timeout wasn't there)

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im also facing this issue
my idea is to keep SMTP client instance in memory because i dont want to spend time connecting & doing login to a server each time i want to send a message

my steps to reproduce are:

1. create SMTP client instance

smtp_client = SMTP(...)

2. connect to an SMTP server (i use mailslurper for development) and send a message

if not smtp_client.is_connected:
   await smtp_client.connect(timeout=10)

smtp_client.send_message(message)

3. intentionally stop SMTP server
4. try to repeat step 2. when calling await smtp_client.connect the program hangs infinitely

from aiosmtplib.

I think that's the exact problem I had

from aiosmtplib.

i did some digging and found out that this is the place where program hangs
so we need to explicitly release _connect_lock in order to be able to reconnect again
this code seems to work

if not smtp_client.is_connected:
    if smtp_client._connect_lock and smtp_client._connect_lock.locked():
        smtp_client.close()

    await smtp_client.connect()

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