Background worker to send notifications

hc/api/admin.py

@@ -2,6 +2,7 @@ from django.contrib import admin
 
 from hc.api.models import Check
 
+
 @admin.register(Check)
 class ChecksAdmin(admin.ModelAdmin):
     list_display = ("id", "code", "user", "last_ping")

hc/api/management/commands/ensuretriggers.py

@@ -0,0 +1,27 @@
+from django.core.management.base import BaseCommand
+from django.db import connection
+
+
+class Command(BaseCommand):
+    help = 'Ensures triggers exist in database'
+
+    def handle(self, *args, **options):
+        cursor = connection.cursor()
+
+        cursor.execute("""
+CREATE OR REPLACE FUNCTION update_alert_after()
+RETURNS trigger AS $update_alert_after$
+    BEGIN
+        IF NEW.last_ping IS NOT NULL THEN
+            NEW.alert_after := NEW.last_ping + NEW.timeout;
+        END IF;
+        RETURN NEW;
+    END;
+$update_alert_after$ LANGUAGE plpgsql;
+
+DROP TRIGGER IF EXISTS update_alert_after ON api_check;
+
+CREATE TRIGGER update_alert_after
+BEFORE INSERT OR UPDATE OF last_ping, timeout  ON api_check
+FOR EACH ROW EXECUTE PROCEDURE update_alert_after();
+        """)

hc/api/management/commands/sendalerts.py

@@ -0,0 +1,45 @@
+import sys
+import time
+
+from django.core.management.base import BaseCommand
+from django.utils import timezone
+
+from hc.api.models import Check
+from hc.lib.emails import send_status_notification
+
+
+def _log(message):
+    sys.stdout.write(message)
+    sys.stdout.flush()
+
+
+class Command(BaseCommand):
+    help = 'Ensures triggers exist in database'
+
+    def handle(self, *args, **options):
+
+        while True:
+            # Gone down?
+            query = Check.objects
+            query = query.filter(alert_after__lt=timezone.now())
+            query = query.filter(enabled=True, status="up")
+            for check in query:
+                check.status = "down"
+                check.save()
+
+                _log("\nSending email about going down for %s\n" % check.code)
+                send_status_notification(check)
+
+            # Gone up?
+            query = Check.objects
+            query = query.filter(alert_after__gt=timezone.now())
+            query = query.filter(enabled=True, status="down")
+            for check in query:
+                check.status = "up"
+                check.save()
+
+                _log("\nSending email about going up for %s\n" % check.code)
+                send_status_notification(check)
+
+            time.sleep(1)
+            _log(".")

hc/api/migrations/0002_auto_20150616_0732.py

@@ -0,0 +1,35 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+import datetime
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('api', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='check',
+            name='alert_after',
+            field=models.DateTimeField(null=True, blank=True),
+        ),
+        migrations.AddField(
+            model_name='check',
+            name='enabled',
+            field=models.BooleanField(default=True),
+        ),
+        migrations.AddField(
+            model_name='check',
+            name='status',
+            field=models.CharField(max_length=6, choices=[('up', 'Up'), ('down', 'Down'), ('new', 'New')], default='new'),
+        ),
+        migrations.AddField(
+            model_name='check',
+            name='timeout',
+            field=models.DurationField(choices=[(datetime.timedelta(0, 300), '5 minutes'), (datetime.timedelta(0, 600), '10 minutes'), (datetime.timedelta(0, 1800), '30 minutes'), (datetime.timedelta(0, 3600), '1 hour'), (datetime.timedelta(0, 7200), '2 hours'), (datetime.timedelta(0, 21600), '6 hours'), (datetime.timedelta(0, 43200), '12 hours'), (datetime.timedelta(1), '1 day'), (datetime.timedelta(2), '2 days'), (datetime.timedelta(7), '1 week'), (datetime.timedelta(14), '2 weeks')], default=datetime.timedelta(1)),
+        ),
+    ]

hc/api/models.py

@@ -1,10 +1,31 @@
+from datetime import timedelta as td
 import uuid
 
 from django.contrib.auth.models import User
 from django.db import models
 
+STATUSES = (("up", "Up"), ("down", "Down"), ("new", "New"))
+ONEDAY = td(days=1)
+DURATIONS = (
+    (td(minutes=5),  "5 minutes"),
+    (td(minutes=10), "10 minutes"),
+    (td(minutes=30), "30 minutes"),
+    (td(hours=1),    "1 hour"),
+    (td(hours=2),    "2 hours"),
+    (td(hours=6),    "6 hours"),
+    (td(hours=12),   "12 hours"),
+    (ONEDAY,         "1 day"),
+    (td(days=2),     "2 days"),
+    (td(weeks=1),    "1 week"),
+    (td(weeks=2),    "2 weeks")
+)
+
 
 class Check(models.Model):
     code = models.UUIDField(default=uuid.uuid4, editable=False)
     user = models.ForeignKey(User)
+    enabled = models.BooleanField(default=True)
+    timeout = models.DurationField(default=ONEDAY)
     last_ping = models.DateTimeField(null=True, blank=True)
+    alert_after = models.DateTimeField(null=True, blank=True, editable=False)
+    status = models.CharField(max_length=6, choices=STATUSES, default="new")

hc/api/views.py

@@ -11,6 +11,9 @@ def ping(request, code):
         return HttpResponseBadRequest()
 
     check.last_ping = timezone.now()
+    if check.status == "new":
+        check.status = "up"
+
     check.save()
 
     return HttpResponse()

hc/lib/emails.py

@@ -0,0 +1,15 @@
+from django.core.mail import send_mail
+
+
+def send_status_notification(check):
+    if check.status == "down":
+        subject = "Alert DOWN"
+        body = "Hi, the check %s has gone down" % check.code
+    elif check.status == "up":
+        subject = "Alert UP"
+        body = "Hi, the check %s has gone up" % check.code
+    else:
+        raise NotImplemented("Unexpected status: %s" % check.status)
+
+    send_mail(subject, body, '[email protected]', [check.user.email],
+              fail_silently=False)

hc/settings.py

@@ -85,7 +85,7 @@ DATABASES = {
         'NAME':     'hc',
         'USER':     'hc',
         'PASSWORD': '',
-        'HOST':     '192.168.1.111',
+        'HOST':     '192.168.1.112',
         'PORT':     5432,
         'TEST': {'CHARSET': 'UTF8'}
     }