From 8fedd9ec0729733c74ed95cdc3c92e7c4ddea784 Mon Sep 17 00:00:00 2001
From: Jens Langhammer <jens.langhammer@beryju.org>
Date: Fri, 16 Oct 2020 14:31:01 +0200
Subject: [PATCH] stages/email: Implement MonitoredTask, but only for failed
 emails

---
 passbook/lib/tasks.py          | 25 ++++++++++--------
 passbook/stages/email/tasks.py | 47 ++++++++++++++++++++++++----------
 2 files changed, 48 insertions(+), 24 deletions(-)

diff --git a/passbook/lib/tasks.py b/passbook/lib/tasks.py
index 0960d24e9..0e837c559 100644
--- a/passbook/lib/tasks.py
+++ b/passbook/lib/tasks.py
@@ -69,10 +69,14 @@ class TaskInfo:
 class MonitoredTask(Task):
     """Task which can save its state to the cache"""
 
+    # For tasks that should only be listed if they failed, set this to False
+    save_on_success: bool
+
     _result: TaskResult
 
     def __init__(self, *args, **kwargs) -> None:
         super().__init__(*args, **kwargs)
+        self.save_on_success = True
         self._result = TaskResult(status=TaskResultStatus.ERROR, messages=[])
 
     def set_status(self, result: TaskResult):
@@ -83,16 +87,17 @@ class MonitoredTask(Task):
     def after_return(
         self, status, retval, task_id, args: List[Any], kwargs: Dict[str, Any], einfo
     ):
-        TaskInfo(
-            task_name=self.__name__,
-            task_description=self.__doc__,
-            finish_timestamp=datetime.now(),
-            result=self._result,
-            task_call_module=self.__module__,
-            task_call_func=self.__name__,
-            task_call_args=args,
-            task_call_kwargs=kwargs,
-        ).save()
+        if self.save_on_success:
+            TaskInfo(
+                task_name=self.__name__,
+                task_description=self.__doc__,
+                finish_timestamp=datetime.now(),
+                result=self._result,
+                task_call_module=self.__module__,
+                task_call_func=self.__name__,
+                task_call_args=args,
+                task_call_kwargs=kwargs,
+            ).save()
         return super().after_return(status, retval, task_id, args, kwargs, einfo=einfo)
 
     # pylint: disable=too-many-arguments
diff --git a/passbook/stages/email/tasks.py b/passbook/stages/email/tasks.py
index d2a10b482..89a2ce813 100644
--- a/passbook/stages/email/tasks.py
+++ b/passbook/stages/email/tasks.py
@@ -1,11 +1,14 @@
 """email stage tasks"""
+from email.utils import make_msgid
 from smtplib import SMTPException
 from typing import Any, Dict, List
 
 from celery import group
 from django.core.mail import EmailMultiAlternatives
+from django.core.mail.utils import DNS_NAME
 from structlog import get_logger
 
+from passbook.lib.tasks import MonitoredTask, TaskResult, TaskResultStatus
 from passbook.root.celery import CELERY_APP
 from passbook.stages.email.models import EmailStage
 
@@ -16,7 +19,7 @@ def send_mails(stage: EmailStage, *messages: List[EmailMultiAlternatives]):
     """Wrapper to convert EmailMessage to dict and send it from worker"""
     tasks = []
     for message in messages:
-        tasks.append(_send_mail_task.s(stage.pk, message.__dict__))
+        tasks.append(send_mail.s(stage.pk, message.__dict__))
     lazy_group = group(*tasks)
     promise = lazy_group()
     return promise
@@ -29,19 +32,35 @@ def send_mails(stage: EmailStage, *messages: List[EmailMultiAlternatives]):
         ConnectionError,
     ),
     retry_backoff=True,
+    base=MonitoredTask,
 )
-# pylint: disable=unused-argument
-def _send_mail_task(self, email_stage_pk: int, message: Dict[Any, Any]):
+def send_mail(self: MonitoredTask, email_stage_pk: int, message: Dict[Any, Any]):
     """Send Email according to EmailStage parameters from background worker.
     Automatically retries if message couldn't be sent."""
-    stage: EmailStage = EmailStage.objects.get(pk=email_stage_pk)
-    backend = stage.backend
-    backend.open()
-    # Since django's EmailMessage objects are not JSON serialisable,
-    # we need to rebuild them from a dict
-    message_object = EmailMultiAlternatives()
-    for key, value in message.items():
-        setattr(message_object, key, value)
-    message_object.from_email = stage.from_address
-    LOGGER.debug("Sending mail", to=message_object.to)
-    stage.backend.send_messages([message_object])
+    self.save_on_success = False
+    try:
+        stage: EmailStage = EmailStage.objects.get(pk=email_stage_pk)
+        backend = stage.backend
+        backend.open()
+        # Since django's EmailMessage objects are not JSON serialisable,
+        # we need to rebuild them from a dict
+        message_object = EmailMultiAlternatives()
+        for key, value in message.items():
+            setattr(message_object, key, value)
+        message_object.from_email = stage.from_address
+        # Because we use the Message-ID as UID for the task, manually assign it
+        message_id = make_msgid(DNS_NAME)
+        message_object.extra_headers["Message-ID"] = message_id
+
+        LOGGER.debug("Sending mail", to=message_object.to)
+        stage.backend.send_messages([message_object])
+        self.set_status(
+            TaskResult(
+                TaskResultStatus.SUCCESSFUL,
+                messages=["Successfully sent Mail."],
+                uid=message_id,
+            )
+        )
+    except (SMTPException, ConnectionError) as exc:
+        self.set_status(TaskResult(TaskResultStatus.ERROR, [str(exc)], exc))
+        raise exc