Merge ~andreserl/maas:prometheus_handler into maas:master

[Andres Rodriguez]

Add handler to provide a metrics endpoint on /MAAS/metrics.

[MAAS Lander (maas-lander)]

UNIT TESTS
-b prometheus_handler lp:~andreserl/maas/+git/maas into -b master lp:~maas-committers/maas

STATUS: SUCCESS
COMMIT: 98432fd6bdc4f23b0e5357fa3c1d4398cc51d724

review: Approve

[MAAS Lander (maas-lander)]

UNIT TESTS
-b prometheus_handler lp:~andreserl/maas/+git/maas into -b master lp:~maas-committers/maas

STATUS: SUCCESS
COMMIT: bb37acc8271eb45cbe1749f6fc272d55d3a8f4a7

review: Approve

[Mike Pontillo (mpontillo)]

Looks good; I have a couple minor suggestions below.

review: Approve

[Newell Jensen (newell-jensen)]

LGTM, one inline question, not going to block.

review: Approve

[Andres Rodriguez (andreserl)]

addressed comments, which can be handled in a follow up branch.

[MAAS Lander (maas-lander)]

LANDING
-b prometheus_handler lp:~andreserl/maas/+git/maas into -b master lp:~maas-committers/maas

STATUS: FAILED BUILD
LOG: http://maas-ci-jenkins.internal:8080/job/maas/job/branch-tester/4242/consoleText

e5eacbf... by Andres Rodriguez on 2018-10-18

Fix tests

diff --git a/src/maasserver/middleware.py b/src/maasserver/middleware.py
index bcad2e8..1de6072 100644
--- a/src/maasserver/middleware.py
+++ b/src/maasserver/middleware.py
@@ -75,6 +75,8 @@ PUBLIC_URL_PREFIXES = [
     reverse('metadata'),
     # RPC information is for use by rack controllers; no login.
     reverse('rpc-info'),
+    # Prometheus stats
+    reverse('metrics'),
     # API meta-information is publicly visible.
     reverse('api_version'),
     reverse('api_v1_error'),
diff --git a/src/maasserver/prometheus.py b/src/maasserver/prometheus.py
index d30aad3..55c58df 100644
--- a/src/maasserver/prometheus.py
+++ b/src/maasserver/prometheus.py
@@ -11,6 +11,10 @@ __all__ = [
 from datetime import timedelta
 import json
 
+from django.http import (
+    HttpResponse,
+    HttpResponseNotFound,
+)
 from maasserver.models import Config
 from maasserver.stats import get_maas_stats
 from maasserver.utils.orm import transactional
@@ -24,6 +28,7 @@ try:
         CollectorRegistry,
         Gauge,
         push_to_gateway,
+        generate_latest,
     )
     PROMETHEUS = True
 except:
@@ -32,13 +37,22 @@ except:
 log = LegacyLogger()
 
 
+def prometheus_handler(request):
+    if not Config.objects.get_config('prometheus_enabled'):
+        return HttpResponseNotFound()
+
+    return HttpResponse(
+        content=generate_latest(get_stats_for_prometheus()),
+        content_type="text/plain")
+
+
 def get_stats_for_prometheus():
     registry = CollectorRegistry()
     stats = json.loads(get_maas_stats())
 
     # Gather counter for machines per status
     counter = Gauge(
-        "machine_status", "Number per machines per stats",
+        "machine_status", "Number of machines per status",
         ["status"], registry=registry)
     for status, machines in stats['machine_status'].items():
         counter.labels(status).set(machines)
diff --git a/src/maasserver/tests/test_prometheus.py b/src/maasserver/tests/test_prometheus.py
index 66c1af6..fc93872 100644
--- a/src/maasserver/tests/test_prometheus.py
+++ b/src/maasserver/tests/test_prometheus.py
@@ -5,6 +5,7 @@
 
 __all__ = []
 
+import http.client
 import json
 
 from django.db import transaction
@@ -19,6 +20,7 @@ from maasserver.testing.testcase import (
     MAASServerTestCase,
     MAASTransactionServerTestCase,
 )
+from maasserver.utils.django_urls import reverse
 from maastesting.matchers import (
     MockCalledOnce,
     MockCalledOnceWith,
@@ -31,6 +33,36 @@ from twisted.application.internet import TimerService
 from twisted.internet.defer import fail
 
 
+class TestPrometheusHandler(MAASServerTestCase):
+
+    def test_prometheus_handler_returns_http_not_found(self):
+        Config.objects.set_config('prometheus_enabled', False)
+        response = self.client.get(reverse('metrics'))
+        self.assertEqual("text/html; charset=utf-8", response["Content-Type"])
+        self.assertEquals(response.status_code, http.client.NOT_FOUND)
+
+    def test_prometheus_handler_returns_success(self):
+        Config.objects.set_config('prometheus_enabled', True)
+        self.patch(prometheus, "CollectorRegistry")
+        self.patch(prometheus, "Gauge")
+        self.patch(prometheus, "generate_latest").return_value = {}
+        response = self.client.get(reverse('metrics'))
+        self.assertEqual("text/plain", response["Content-Type"])
+        self.assertEquals(response.status_code, http.client.OK)
+
+    def test_prometheus_handler_returns_metrics(self):
+        Config.objects.set_config('prometheus_enabled', True)
+        metrics = (
+            '# HELP machine_status Number per machines per stats'
+            '# TYPE machine_status counter'
+            'machine_status={status="deployed"} 100')
+        self.patch(prometheus, "CollectorRegistry")
+        self.patch(prometheus, "Gauge")
+        self.patch(prometheus, "generate_latest").return_value = metrics
+        response = self.client.get(reverse('metrics'))
+        self.assertEqual(metrics, response.content.decode("unicode_escape"))
+
+
 class TestPrometheus(MAASServerTestCase):
 
     def test_get_stats_for_prometheus(self):
diff --git a/src/maasserver/urls.py b/src/maasserver/urls.py
index 6c9c849..14dda55 100755
--- a/src/maasserver/urls.py
+++ b/src/maasserver/urls.py
@@ -21,6 +21,7 @@ from maasserver.bootresources import (
     simplestreams_stream_handler,
 )
 from maasserver.macaroon_auth import MacaroonDischargeRequest
+from maasserver.prometheus import prometheus_handler
 from maasserver.views import (
     settings,
     TextTemplateView,
@@ -83,6 +84,7 @@ urlpatterns += [
         r'^images-stream/(?P<os>.*)/(?P<arch>.*)/(?P<subarch>.*)/'
         '(?P<series>.*)/(?P<version>.*)/(?P<filename>.*)$',
         simplestreams_file_handler, name='simplestreams_file_handler'),
+    url(r'^metrics$', prometheus_handler, name='metrics'),
     url(
         r'^robots\.txt$', TextTemplateView.as_view(
             template_name='maasserver/robots.txt'),