Refactored Alert model to support alerts without observer.

This change includes a slight api change in the way how Alert.set and
Alert.clear is called. In addtion, the way how waiting_period works is
improved and more clear. A waiting_period of zero means immediate
critical notification without warning.

howl/admin.py

@@ -1,5 +1,4 @@
 from django.contrib import admin
-from django.utils.translation import ugettext_lazy as _
 
 from .models import Alert, Observer
 
@@ -11,10 +10,5 @@ class ObserverAdmin(admin.ModelAdmin):
 
 @admin.register(Alert)
 class AlertAdmin(admin.ModelAdmin):
-    list_display = ('get_observer_name', 'timestamp', 'value', 'state')
+    list_display = ('identifier', 'timestamp', 'value', 'state')
     list_filter = ('state',)
-
-    def get_observer_name(self, obj):
-        return obj.observer.name
-
-    get_observer_name.short_description = _('Observer')

howl/locale/de/LC_MESSAGES/django.po

@@ -7,21 +7,17 @@ msgid ""
 msgstr ""
 "Project-Id-Version: \n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2016-02-10 08:14+0100\n"
-"PO-Revision-Date: 2016-02-10 08:14+0100\n"
+"POT-Creation-Date: 2016-02-10 21:40+0100\n"
+"PO-Revision-Date: 2016-02-10 21:40+0100\n"
+"Last-Translator: \n"
+"Language-Team: \n"
 "Language: de\n"
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=UTF-8\n"
 "Content-Transfer-Encoding: 8bit\n"
 "Plural-Forms: nplurals=2; plural=(n != 1);\n"
-"Last-Translator: \n"
-"Language-Team: \n"
 "X-Generator: Poedit 1.8.6\n"
 
-#: admin.py:20 models.py:20 models.py:47
-msgid "Observer"
-msgstr "Beobachter"
-
 #: apps.py:7
 msgid "Howl"
 msgstr "Howl"
@@ -34,50 +30,58 @@ msgstr "Name"
 msgid "Operator type"
 msgstr "Operator Typ"
 
-#: models.py:15 models.py:49
+#: models.py:15 models.py:52
 msgid "Value"
 msgstr "Wert"
 
-#: models.py:16
+#: models.py:17
 msgid "Waiting period"
 msgstr "Wartezeit"
 
-#: models.py:16
+#: models.py:17
 msgid "In seconds"
 msgstr "In Sekunden"
 
-#: models.py:17
+#: models.py:18
 msgid "Alert every time"
 msgstr "Jedes mal alarmieren"
 
 #: models.py:21
+msgid "Observer"
+msgstr "Beobachter"
+
+#: models.py:22
 msgid "Observers"
 msgstr "Beobachter"
 
-#: models.py:43
+#: models.py:47
 msgid "Waiting"
 msgstr "Wartend"
 
-#: models.py:44
+#: models.py:48
 msgid "Notified"
 msgstr "Benachrichtigt"
 
-#: models.py:51
+#: models.py:50
+msgid "Identifier"
+msgstr "Kennung"
+
+#: models.py:54
 msgid "State"
 msgstr "Status"
 
-#: models.py:54
+#: models.py:57
 msgid "Alert"
 msgstr "Alarm"
 
-#: models.py:55
+#: models.py:58
 msgid "Alerts"
 msgstr "Alarme"
 
-#: models.py:59
+#: models.py:62
 #, python-brace-format
-msgid "Alert (ID: {0}) for {1}"
-msgstr "Alarm (ID: {0}) für {1}"
+msgid "Alert for {0}"
+msgstr "Alarm für {0}"
 
 #: operators.py:50
 msgid "Equals"

howl/migrations/0005_auto_20160210_2042.py

@@ -0,0 +1,34 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('howl', '0004_auto_20160210_0811'),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name='alert',
+            name='observer',
+        ),
+        migrations.AddField(
+            model_name='alert',
+            name='identifier',
+            field=models.CharField(default='', verbose_name='Identifier', max_length=64, unique=True),
+            preserve_default=False,
+        ),
+        migrations.AlterField(
+            model_name='alert',
+            name='value',
+            field=models.CharField(verbose_name='Value', blank=True, null=True, max_length=255),
+        ),
+        migrations.AlterField(
+            model_name='observer',
+            name='value',
+            field=models.IntegerField(verbose_name='Value'),
+        ),
+    ]

howl/models.py

@@ -12,8 +12,9 @@ class Observer(models.Model):
     name = models.CharField(_('Name'), max_length=255)
     operator = models.CharField(
         _('Operator type'), max_length=32, choices=get_operator_types())
-    value = models.PositiveIntegerField(_('Value'))
-    waiting_period = models.PositiveIntegerField(_('Waiting period'), help_text=_('In seconds'))
+    value = models.IntegerField(_('Value'))
+    waiting_period = models.PositiveIntegerField(
+        _('Waiting period'), help_text=_('In seconds'))
     alert_every_time = models.BooleanField(_('Alert every time'), default=False)
 
     class Meta:
@@ -24,14 +25,17 @@ class Meta:
     def __str__(self):
         return self.name
 
+    def get_alert_identifier(self):
+        return 'howl-observer:{0}'.format(self.pk)
+
     def get_alert(self, compare_value, **kwargs):
         operator_class = get_operator_class(self.operator)
 
         if operator_class(self).compare(compare_value):
-            Alert.clear(self, compare_value, **kwargs)
+            Alert.clear(compare_value, observer=self, **kwargs)
             return None
 
-        return Alert.set(self, compare_value, **kwargs)
+        return Alert.set(compare_value, observer=self, **kwargs)
 
     def compare(self, compare_value, **kwargs):
         return self.get_alert(compare_value, **kwargs) is None
@@ -43,10 +47,9 @@ class Alert(models.Model):
         (STATE_WAITING, _('Waiting')),
         (STATE_NOTIFIED, _('Notified')),
     )
-
-    observer = models.ForeignKey(Observer, verbose_name=_('Observer'))
+    identifier = models.CharField(_('Identifier'), max_length=64, unique=True)
     timestamp = models.DateTimeField(auto_now_add=True)
-    value = models.CharField(_('Value'), max_length=255)
+    value = models.CharField(_('Value'), max_length=255, blank=True, null=True)
     state = models.PositiveSmallIntegerField(
         _('State'), choices=STATE_CHOICES, default=STATE_WAITING)
 
@@ -56,40 +59,56 @@ class Meta:
         ordering = ('-timestamp',)
 
     def __str__(self):
-        return _('Alert (ID: {0}) for {1}').format(self.pk, self.observer.name)
+        return _('Alert for {0}').format(self.identifier)
 
     @classmethod
-    def set(cls, observer, compare_value, **kwargs):
+    def set(cls, value=None, **kwargs):
+        if 'observer' in kwargs:
+            identifier = kwargs['observer'].get_alert_identifier()
+            waiting_period = kwargs['observer'].waiting_period
+            alert_every_time = kwargs['observer'].alert_every_time
+        else:
+            if 'identifier' not in kwargs:
+                raise ValueError('`observer` or `identifier` required.')
+            identifier = kwargs['identifier']
+            waiting_period = kwargs.get('waiting_period', 0)
+            alert_every_time = kwargs.get('alert_every_time', False)
+
         obj, created = Alert.objects.get_or_create(
-            observer=observer, defaults={'value': compare_value})
+            identifier=identifier, defaults={'value': value})
 
-        if created:
-            alert_wait.send(sender=cls, instance=obj, compare_value=compare_value, **kwargs)
+        if created and waiting_period > 0:
+            alert_wait.send(sender=cls, instance=obj, value=value, **kwargs)
             return obj
 
-        alert_time = obj.timestamp + timedelta(seconds=observer.waiting_period)
+        alert_time = obj.timestamp + timedelta(seconds=waiting_period)
 
         if alert_time < timezone.now():
-            if obj.state == obj.STATE_NOTIFIED and observer.alert_every_time:
-                obj.value = compare_value
+            if obj.state == obj.STATE_NOTIFIED and alert_every_time:
+                obj.value = value
                 obj.save(update_fields=['value'])
-                alert_notify.send(
-                    sender=cls, instance=obj, compare_value=compare_value, **kwargs)
+                alert_notify.send(sender=cls, instance=obj, value=value, **kwargs)
 
             if obj.state == obj.STATE_WAITING:
-                obj.value = compare_value
+                obj.value = value
                 obj.state = obj.STATE_NOTIFIED
                 obj.save(update_fields=['value', 'state'])
-                alert_notify.send(
-                    sender=cls, instance=obj, compare_value=compare_value, **kwargs)
+                alert_notify.send(sender=cls, instance=obj, value=value, **kwargs)
 
         return obj
 
     @classmethod
-    def clear(cls, observer, compare_value, **kwargs):
+    def clear(cls, value=None, **kwargs):
+        if 'observer' in kwargs:
+            identifier = kwargs['observer'].get_alert_identifier()
+        else:
+            if 'identifier' not in kwargs:
+                raise ValueError('`observer` or `identifier` required.')
+            identifier = kwargs['identifier']
+
         try:
-            obj = Alert.objects.get(observer=observer)
-            alert_clear.send(sender=cls, instance=obj, compare_value=compare_value, **kwargs)
+            obj = Alert.objects.get(identifier=identifier)
+            alert_clear.send(sender=cls, instance=obj, value=value, **kwargs)
             obj.delete()
         except Alert.DoesNotExist:
             pass

howl/tests/factories/observers.py

@@ -16,7 +16,7 @@ class Meta:
 
 
 class AlertFactory(factory.DjangoModelFactory):
-    observer = factory.SubFactory(ObserverFactory)
+    identifier = factory.Sequence(lambda i: 'alert-{0}')
     value = FuzzyChoice(range(1, 10))
 
     class Meta:

howl/tests/test_admin.py

@@ -3,7 +3,6 @@
 
 from howl.admin import AlertAdmin, ObserverAdmin
 from howl.models import Alert, Observer
-from howl.tests.factories.observers import AlertFactory, ObserverFactory
 
 
 @pytest.mark.django_db
@@ -19,11 +18,4 @@ class TestAlertAdmin:
 
     def test_list_display(self, rf):
         modeladmin = AlertAdmin(Alert, admin.site)
-        assert modeladmin.list_display == ('get_observer_name', 'timestamp', 'value', 'state')
-
-    def test_get_observer_name(self, rf):
-        observer = ObserverFactory.create()
-        alert = AlertFactory.create(observer=observer)
-
-        modeladmin = AlertAdmin(Alert, admin.site)
-        assert modeladmin.get_observer_name(alert) == observer.name
+        assert modeladmin.list_display == ('identifier', 'timestamp', 'value', 'state')