Experimental Prometheus metrics endpoint. cc: #300

CHANGELOG.md

@@ -1,10 +1,11 @@
 # Changelog
 All notable changes to this project will be documented in this file.
 
-## v1.14.0 - Unreleased
+## v1.14.0-dev - Unreleased
 
 ### Improvements
 - Improved UI to invite users from account's other projects (#258)
+- Experimental Prometheus metrics endpoint (#300)
 
 ### Bug Fixes
 - The "render_docs" command checks if markdown and pygments is installed (#329)

hc/api/models.py

@@ -199,6 +199,11 @@ class Check(models.Model):
         codes = self.channel_set.order_by("code").values_list("code", flat=True)
         return ",".join(map(str, codes))
 
+    @property
+    def unique_key(self):
+        code_half = self.code.hex[:16]
+        return hashlib.sha1(code_half.encode()).hexdigest()
+
     def to_dict(self, readonly=False):
 
         result = {
@@ -216,8 +221,7 @@ class Check(models.Model):
             result["last_duration"] = int(self.last_duration.total_seconds())
 
         if readonly:
-            code_half = self.code.hex[:16]
-            result["unique_key"] = hashlib.sha1(code_half.encode()).hexdigest()
+            result["unique_key"] = self.unique_key
         else:
             update_rel_url = reverse("hc-api-update", args=[self.code])
             pause_rel_url = reverse("hc-api-pause", args=[self.code])

hc/front/tests/test_metrics.py

@@ -0,0 +1,43 @@
+from hc.api.models import Check
+from hc.test import BaseTestCase
+
+
+class MetricsTestCase(BaseTestCase):
+    def setUp(self):
+        super(MetricsTestCase, self).setUp()
+        self.project.api_key_readonly = "R" * 32
+        self.project.save()
+
+        self.check = Check(project=self.project, name="Alice Was Here")
+        self.check.tags = "foo"
+        self.check.save()
+
+        key = "R" * 32
+        self.url = "/projects/%s/checks/metrics/?api_key=%s" % (self.project.code, key)
+
+    def test_it_works(self):
+        r = self.client.get(self.url)
+        self.assertEqual(r.status_code, 200)
+        self.assertContains(r, 'name="Alice Was Here"')
+        self.assertContains(r, 'tags="foo"')
+        self.assertContains(r, 'tag="foo"')
+        self.assertContains(r, "hc_checks_total 1")
+
+    def test_it_escapes_newline(self):
+        self.check.name = "Line 1\nLine2"
+        self.check.tags = "A\\C"
+        self.check.save()
+
+        r = self.client.get(self.url)
+        self.assertEqual(r.status_code, 200)
+        self.assertContains(r, "Line 1\\nLine2")
+        self.assertContains(r, "A\\\\C")
+
+    def test_it_checks_api_key_length(self):
+        r = self.client.get(self.url + "R")
+        self.assertEqual(r.status_code, 400)
+
+    def test_it_checks_api_key(self):
+        url = "/projects/%s/checks/metrics/?api_key=%s" % (self.project.code, "X" * 32)
+        r = self.client.get(url)
+        self.assertEqual(r.status_code, 403)

hc/front/urls.py

@@ -70,6 +70,7 @@ urlpatterns = [
     path("projects/<uuid:code>/checks/add/", views.add_check, name="hc-add-check"),
     path("checks/cron_preview/", views.cron_preview),
     path("projects/<uuid:code>/checks/status/", views.status, name="hc-status"),
+    path("projects/<uuid:code>/checks/metrics/", views.metrics, name="hc-metrics"),
     path("checks/<uuid:code>/", include(check_urls)),
     path("integrations/", include(channel_urls)),
     path("docs/", views.serve_doc, name="hc-docs"),

hc/front/views.py

@@ -1540,3 +1540,50 @@ def add_msteams(request):
 
     ctx = {"page": "channels", "project": request.project, "form": form}
     return render(request, "integrations/add_msteams.html", ctx)
+
+
+def metrics(request, code):
+    api_key = request.GET.get("api_key", "")
+    if len(api_key) != 32:
+        return HttpResponseBadRequest()
+
+    q = Project.objects.filter(code=code, api_key_readonly=api_key)
+    try:
+        project = q.get()
+    except Project.DoesNotExist:
+        return HttpResponseForbidden()
+
+    checks = Check.objects.filter(project_id=project.id).order_by("id")
+
+    def esc(s):
+        return s.replace("\\", "\\\\").replace('"', '\\"').replace("\n", "\\n")
+
+    def output(checks):
+        yield "# HELP hc_check_up Whether the check is currently up (1 for yes, 0 for no).\n"
+        yield "# TYPE hc_check_up gauge\n"
+
+        TMPL = """hc_check_up{name="%s", tags="%s", unique_key="%s"} %d\n"""
+        for check in checks:
+            value = 0 if check.get_status(with_started=False) == "down" else 1
+            yield TMPL % (esc(check.name), esc(check.tags), check.unique_key, value)
+
+        tags_statuses, num_down = _tags_statuses(checks)
+        yield "\n"
+        yield "# HELP hc_tag_up Whether all checks with this tag are up (1 for yes, 0 for no).\n"
+        yield "# TYPE hc_tag_up gauge\n"
+        TMPL = """hc_tag_up{tag="%s"} %d\n"""
+        for tag in sorted(tags_statuses):
+            value = 0 if tags_statuses[tag] == "down" else 1
+            yield TMPL % (esc(tag), value)
+
+        yield "\n"
+        yield "# HELP hc_checks_total The total number of checks.\n"
+        yield "# TYPE hc_checks_total gauge\n"
+        yield "hc_checks_total %d\n" % len(checks)
+        yield "\n"
+
+        yield "# HELP hc_checks_down_total The number of checks currently down.\n"
+        yield "# TYPE hc_checks_down_total gauge\n"
+        yield "hc_checks_down_total %d\n" % num_down
+
+    return HttpResponse(output(checks), content_type="text/plain")

templates/accounts/project.html

@@ -43,6 +43,10 @@
                             API key (read-only): <br />
                             <code>{{ project.api_key_readonly }}</code>
                         </p>
+                        <p>
+                            Prometheus metrics endpoint:
+                            <a href="{% url 'hc-metrics' project.code %}?api_key={{ project.api_key_readonly }}">here</a>
+                        </p>
                         {% endif %}
                         <button
                             data-toggle="modal"