Mail delivery may take too long under some circumstances

[CarolinaFernandez]

Django's send_mail method is used "at it is", but no check is being made in case of any of the following happens:

• Bad mail server configuration
• Server takes too long to send mail (timeout)
• ...

For example, with the new plugin system an e-mail will be sent if some errors are found in the topology; but this should not affect the load page, which is already mildly high.

Operations like these that do not affect normal flow may be rather dispatched to background...

[CarolinaFernandez]

In order to modify the minimum possible quantity of code, a new Expedient send_mail (wrapper) method was made; which invokes a thread to use the Django's normal send_mail with the given parameters. Every call to send_mail (within django.core.mail) was replaced by this new method.

File: expedient/src/python/expedient/common/utils/mail.py

def send_mail(subject, message, from_email, recipient_list):
    """
    Wrapper for the send_mail method within django.core.mail
    which uses a thread to decouple its execution from the
    main program. This is specially useful if mail server
    configuration is erroneus, server is very busy, etc; so
    normal flow will not be affected.
    """
    ServiceThread.start_method_new_thread(
                                          django__send_mail,
                                          None,
                                          None,
                                          subject,
                                          message,
                                          from_email,
                                          recipient_list,
                                         )

File: expedient/src/python/expedient/common/utils/ServiceThread.py

from threading import Thread

class ServiceThread(Thread):

    __method = None
    __params = None
    callback_url = None
    request_user = None

    @staticmethod
    def start_method_new_thread(method, request_user = None, url = None, *params):
        thread = ServiceThread()
        # Add this 2 params if != None
        if request_user:
            thread.request_user = request_user
        if url:
            thread.callback_url = url
        thread.start_method(method, *params)

    def start_method(self, method, *params):
        self.__method = method
        self.__params = params
        self.start()

    def run(self):
        # self.__params is a tuple of arguments. The asterisk ("*")
        # converts this tuple into a series of arguments
        try:
            self.__method(*self.__params)
        except Exception as e:
            print "[WARNING] ServiceThread could not execute %s(%s).
                Details: %s" % (str(self.__method), str(self.__params), str(e))