Media refactor: prep for sending SMSes in addition to email

README.md

@@ -53,6 +53,14 @@ A recap of the environment variables that can be set by default follows.
 * SECRET_KEY, used internally by django, should be about 50 chars of ascii
   noise (but avoid backspaces!)
 
+There are also settings (not env-variables) for which notification plugins to use:
+
+DEFAULT_SMS_MEDIA, which by default is unset, since there is no standardized
+way of sending SMSes. See **Notifications and notification plugins**.
+
+DEFAULT_EMAIL_MEDIA, which is included and uses Django's email backend. It is
+better to switch out the email backend than replcaing this plugin.
+
 *A Gmail account with "Allow less secure apps" turned on, was used in the development of this project.*
 
 ### Running tests
@@ -391,3 +399,9 @@ All endpoints require requests to contain a header with key `Authorization` and
 
 ### ER diagram
 ![ER diagram](img/ER_model.png)
+
+## Notifications and notification plugins
+
+A notification plugin is a class that inherits from `argus.notificationprofile.media.base.NotificationMedium`. It has a `send(incident, user, **kwargs)` static method that does the actual sending.
+
+The included `argus.notificationprofile.media.email.EmailNotification` needs only `incident` and `user`, while an SMS medium in addition needs a `phone_number`. A `phone_number` is a string that includes the international calling code, see for instance [Wikipedia: List of mobile telephone prefixes by country](https://en.wikipedia.org/wiki/List_of_mobile_telephone_prefixes_by_country).

src/argus/incident/views.py

@@ -10,7 +10,8 @@
 
 from argus.auth.models import User
 from argus.drf.permissions import IsOwnerOrReadOnly, IsSuperuserOrReadOnly
-from argus.notificationprofile.notification_media import background_send_notifications_to_users
+from argus.notificationprofile.media import background_send_notifications_to_users
+
 from . import mappings
 from .forms import AddSourceSystemForm
 from .models import (

src/argus/notificationprofile/media/__init__.py

@@ -0,0 +1,93 @@
+import importlib
+import logging
+from multiprocessing import Process
+from typing import List
+
+from django.conf import settings
+from django.db import connections
+
+from argus.auth.models import User
+from argus.incident.models import Incident
+
+from ..models import NotificationProfile
+from .email import EmailNotification
+
+
+LOG = logging.getLogger(__name__)
+
+
+__all__ = [
+    "send_notifications_to_users",
+    "background_send_notifications_to_users",
+    "send_notification",
+    "get_notification_media",
+]
+
+
+# Poor mans's plugins
+MEDIA_CLASSES = {
+    NotificationProfile.Media.EMAIL: getattr(settings, "DEFAULT_EMAIL_MEDIA", EmailNotification),
+    NotificationProfile.Media.SMS: getattr(settings, "DEFAULT_SMS_MEDIA", None),
+    NotificationProfile.Media.SLACK: getattr(settings, "DEFAULT_SLACK_MEDIA", None),
+}
+
+
+def _import_class_from_dotted_path(dotted_path: str):
+    module_name, class_name = dotted_path.rsplit('.', 1)
+    module = importlib.import_module(module_name)
+    class_ = getattr(module, class_name)
+    return class_
+
+
+for media_type, media_class in MEDIA_CLASSES.items():
+    if not media_class or not isinstance(media_class, str):
+        continue
+    # Dotted paths here!
+    # TODO: Raise Incident if media_class not importable
+    MEDIA_CLASSES[media_type] = _import_class_from_dotted_path(media_class)
+
+
+def send_notifications_to_users(incident: Incident):
+    if not getattr(settings, "SEND_NOTIFICATIONS", False):
+        LOG.info('Notification: turned off sitewide, not sending for "%s"', incident)
+        return
+    # TODO: only send one notification per medium per user
+    LOG.info('Notification: sending incident "%s"', incident)
+    for profile in NotificationProfile.objects.select_related("user"):
+        if profile.incident_fits(incident):
+            send_notification(profile.user, profile, incident)
+    else:
+        LOG.info('Notification: no listeners for "%s"', incident)
+        return
+    LOG.info('Notification: incident "%s" sent!', incident)
+
+
+def background_send_notifications_to_users(incident: Incident):
+    connections.close_all()
+    LOG.info('Notification: backgrounded: about to send incident "%s"', incident)
+    p = Process(target=send_notifications_to_users, args=(incident,))
+    p.start()
+    return p
+
+
+def send_notification(user: User, profile: NotificationProfile, incident: Incident):
+    media = get_notification_media(profile.media)
+    for medium in media:
+        if medium is not None:
+            medium.send(incident, user, phone_number=profile.phone_number)
+    else:
+        LOG.warn("Notification: Could not send notification, nowhere to send it to")
+
+
+def get_notification_media(model_representations: List[str]):
+    # This will never be a long list
+    media = [
+        MEDIA_CLASSES[representation]
+        for representation in model_representations
+        if MEDIA_CLASSES[representation]
+    ]
+    if media:
+        return media
+    LOG.error("Notification: nowhere to send notifications!")
+    # TODO: Store error as incident
+    return ()

src/argus/notificationprofile/media/base.py

@@ -0,0 +1,14 @@
+from abc import ABC, abstractmethod
+
+from argus.auth.models import User
+from argus.incident.models import Incident
+
+
+__all__ = ['NotificationMedium']
+
+
+class NotificationMedium(ABC):
+    @staticmethod
+    @abstractmethod
+    def send(incident: Incident, user: User, **kwargs):
+        pass

src/argus/notificationprofile/media/email.py

@@ -0,0 +1,57 @@
+import json
+import logging
+
+from django.conf import settings
+from django.template.loader import render_to_string
+from rest_framework.renderers import JSONRenderer
+
+from argus.incident.serializers import IncidentSerializer
+
+from .base import NotificationMedium
+
+
+LOG = logging.getLogger(__name__)
+
+__all__ = ['EmailNotification']
+
+
+def send_email_safely(function, additional_error=None, *args, **kwargs):
+    try:
+        result = function(*args, **kwargs)
+        return result
+    except ConnectionRefusedError as e:
+        EMAIL_HOST = getattr(settings, "EMAIL_HOST", None)
+        if not EMAIL_HOST:
+            LOG.error("Notification: Email: EMAIL_HOST not set, cannot send")
+        EMAIL_PORT = getattr(settings, "EMAIL_PORT", None)
+        if not EMAIL_PORT:
+            LOG.error("Notification: Email: EMAIL_PORT not set, cannot send")
+        if EMAIL_HOST and EMAIL_PORT:
+            LOG.error('Notification: Email: Connection refused to "%s", port "%s"', EMAIL_HOST, EMAIL_PORT)
+        if additional_error:
+            LOG.error(*additional_error)
+        # TODO: Store error as incident
+
+
+class EmailNotification(NotificationMedium):
+    @staticmethod
+    def send(incident, user, **_):
+        if not user.email:
+            logging.getLogger("django.request").warning(
+                f"Cannot send email notification to user '{user}', as they have not set an email address."
+            )
+
+        title = f"Incident at {incident}"
+        incident_dict = IncidentSerializer(incident, context={IncidentSerializer.NO_PKS_KEY: True}).data
+        # Convert OrderedDicts to dicts
+        incident_dict = json.loads(JSONRenderer().render(incident_dict))
+
+        template_context = {
+            "title": title,
+            "incident_dict": incident_dict,
+            "longest_field_name_length": len(max(incident_dict, key=len)),
+        }
+        subject = f"{settings.NOTIFICATION_SUBJECT_PREFIX}{title}"
+        message = render_to_string("notificationprofile/email.txt", template_context)
+        html_message = render_to_string("notificationprofile/email.html", template_context)
+        send_email_safely(user.email_user, subject=subject, message=message, html_message=html_message)