From edbfd4b437a13da0d15a0b1910a34e413fdf674d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C4=93teris=20Caune?= <cuu508@gmail.com>
Date: Sun, 26 Apr 2020 17:45:50 +0300
Subject: [PATCH] Added /api/v1/metrics/ endpoint, useful for monitoring the
 service itself

---
 CHANGELOG.md                 |  1 +
 hc/api/tests/test_metrics.py | 43 ++++++++++++++++++++++++++++++++++++
 hc/api/tests/test_status.py  | 12 ++++++++++
 hc/api/urls.py               |  1 +
 hc/api/views.py              | 17 +++++++++++++-
 hc/settings.py               |  1 +
 6 files changed, 74 insertions(+), 1 deletion(-)
 create mode 100644 hc/api/tests/test_metrics.py
 create mode 100644 hc/api/tests/test_status.py

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2936923a..ca881c46 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ All notable changes to this project will be documented in this file.
 - Users can edit their existing webhook integrations (#176)
 - Add a "Transfer Ownership" feature in Project Settings
 - In checks list, the pause button asks for confirmation (#356)
+- Added /api/v1/metrics/ endpoint, useful for monitoring the service itself
 
 ### Bug Fixes
 - "Get a single check" API call now supports read-only API keys (#346)
diff --git a/hc/api/tests/test_metrics.py b/hc/api/tests/test_metrics.py
new file mode 100644
index 00000000..72a34544
--- /dev/null
+++ b/hc/api/tests/test_metrics.py
@@ -0,0 +1,43 @@
+from django.test.utils import override_settings
+from django.utils.timezone import now
+from hc.api.models import Check, Flip, Ping
+from hc.test import BaseTestCase
+
+
+@override_settings(METRICS_KEY="foo")
+class MetricsTestCase(BaseTestCase):
+    url = "/api/v1/metrics/"
+
+    def test_it_returns_num_unprocessed_flips(self):
+        check = Check.objects.create(project=self.project, status="down")
+        flip = Flip(owner=check)
+        flip.created = now()
+        flip.old_status = "up"
+        flip.new_status = "down"
+        flip.save()
+
+        r = self.client.get(self.url, HTTP_X_METRICS_KEY="foo")
+        self.assertEqual(r.status_code, 200)
+
+        doc = r.json()
+        self.assertEqual(doc["num_unprocessed_flips"], 1)
+
+    def test_it_returns_max_ping_id(self):
+        check = Check.objects.create(project=self.project, status="down")
+        Ping.objects.create(owner=check, n=1)
+        last_ping = Ping.objects.last()
+
+        r = self.client.get(self.url, HTTP_X_METRICS_KEY="foo")
+        self.assertEqual(r.status_code, 200)
+
+        doc = r.json()
+        self.assertEqual(doc["max_ping_id"], last_ping.id)
+
+    @override_settings(METRICS_KEY=None)
+    def test_it_handles_unset_metrics_key(self):
+        r = self.client.get(self.url, HTTP_X_METRICS_KEY="foo")
+        self.assertEqual(r.status_code, 403)
+
+    def test_it_handles_incorrect_metrics_key(self):
+        r = self.client.get(self.url, HTTP_X_METRICS_KEY="bar")
+        self.assertEqual(r.status_code, 403)
diff --git a/hc/api/tests/test_status.py b/hc/api/tests/test_status.py
new file mode 100644
index 00000000..e47f7d98
--- /dev/null
+++ b/hc/api/tests/test_status.py
@@ -0,0 +1,12 @@
+from hc.test import BaseTestCase
+
+
+class StatusTestCase(BaseTestCase):
+    url = "/api/v1/status/"
+
+    def test_it_works(self):
+        r = self.client.get(self.url)
+        self.assertEqual(r.status_code, 200)
+
+        self.assertNumQueries(1)
+        self.assertEqual(r.content, b"OK")
diff --git a/hc/api/urls.py b/hc/api/urls.py
index 28050a25..bdd72182 100644
--- a/hc/api/urls.py
+++ b/hc/api/urls.py
@@ -37,5 +37,6 @@ urlpatterns = [
         {"tag": "*"},
         name="hc-badge-all",
     ),
+    path("api/v1/metrics/", views.metrics),
     path("api/v1/status/", views.status),
 ]
diff --git a/hc/api/views.py b/hc/api/views.py
index d3728e1a..662feddf 100644
--- a/hc/api/views.py
+++ b/hc/api/views.py
@@ -17,7 +17,7 @@ from django.views.decorators.http import require_POST
 
 from hc.api import schemas
 from hc.api.decorators import authorize, authorize_read, cors, validate_json
-from hc.api.models import Check, Notification, Channel
+from hc.api.models import Flip, Channel, Check, Notification, Ping
 from hc.lib.badges import check_signature, get_badge_svg
 
 
@@ -320,6 +320,21 @@ def bounce(request, code):
     return HttpResponse()
 
 
+def metrics(request):
+    if not settings.METRICS_KEY:
+        return HttpResponseForbidden()
+
+    key = request.META.get("HTTP_X_METRICS_KEY")
+    if key != settings.METRICS_KEY:
+        return HttpResponseForbidden()
+
+    doc = {}
+    doc["max_ping_id"] = Ping.objects.values_list("id", flat=True).last()
+    doc["num_unprocessed_flips"] = Flip.objects.filter(processed__isnull=True).count()
+
+    return JsonResponse(doc)
+
+
 def status(request):
     with connection.cursor() as c:
         c.execute("SELECT 1")
diff --git a/hc/settings.py b/hc/settings.py
index b725da35..7662ea3a 100644
--- a/hc/settings.py
+++ b/hc/settings.py
@@ -28,6 +28,7 @@ def envint(s, default):
 
 
 SECRET_KEY = os.getenv("SECRET_KEY", "---")
+METRICS_KEY = os.getenv("METRICS_KEY")
 DEBUG = envbool("DEBUG", "True")
 ALLOWED_HOSTS = os.getenv("ALLOWED_HOSTS", "*").split(",")
 DEFAULT_FROM_EMAIL = os.getenv("DEFAULT_FROM_EMAIL", "healthchecks@example.org")