Possible Memory Leak after upgrading from Python 3.12 to 3.14.2

[franciscopaglia]

Version: '6.12.5'

After upgrading to the latest Python version, we observed increasing memory usage when sending emails in a tight loop using the SendGrid Python client. With ~3,000 sends in a simple function, process memory grows steadily and does not appear to stabilize.

...
from django.conf import settings
from monitoring.instrumentation import Instrumentation
from sendgrid import Attachment as SendGridAttachment
from sendgrid import Category, Mail, SendGridAPIClient
...

class SendgridMailClient(MailClient):
    def __init__(self) -> None:
        self._templates: dict = settings.EMAIL_TEMPLATES
        self._instrumentation = SendgridMailClientInstrumentation(Instrumentation())
        self._client = SendGridAPIClient(settings.SENDGRID_API_KEY)

    def send_new(self, email_info: MailInfo) -> None:
        email_settings = settings.EMAIL_TEMPLATES[email_info.template_name]

        email_message = Mail(
            from_email=email_settings["from_email"],
            to_emails=email_info.to_email,
        )

        email_message.template_id = email_settings["template_id"][email_info.language_code]

        email_message.category = [Category("transactional"), Category(email_info.template_name)]

        self._add_context(email_info=email_info, email_message=email_message)

        self._add_attachments(email_message=email_message, attachments=email_info.attachments)

        try:
            self._client.send(email_message)
            Instrumentation().logger.info(
                "[SendgridMailClient] Email sent",
                language_code=email_info.language_code,
                template_name=email_info.template_name,
                context=json.dumps(email_info.context),
            )
        except Exception as exception:
            self._instrumentation.email_send_error_new(exception, email_info)
            raise exception

    def _add_attachments(self, email_message: Mail, attachments: list[Attachment]) -> None:
        for attachment in attachments:
            sendgrid_attachment: SendGridAttachment = self._map_sendgrid_attachment(attachment)

            email_message.add_attachment(sendgrid_attachment)

    def _add_context(self, email_info: MailInfo, email_message: Mail) -> None:
        context: dict[str, Any] = email_info.context

        email_message.dynamic_template_data = context

    def _map_sendgrid_attachment(self, attachment: Attachment) -> SendGridAttachment:
        encoded_file_content = base64.b64encode(attachment.content).decode()

        return SendGridAttachment(
            file_content=encoded_file_content,
            file_type=attachment.mimetype,
            file_name=attachment.name,
        )

After removing the _client.send method call for sanity, also confirmed leak disappears.