Merge ~andreserl/maas:prometheus_handler into maas:master

[Andres Rodriguez]

ade2444... by Andres Rodriguez on 2018-10-03

Fix format

b82be99... by Andres Rodriguez on 2018-10-03

Minor fixes

60a99f1... by Andres Rodriguez on 2018-10-15

Fixes

1aea499... by Andres Rodriguez on 2018-10-15

Fix lint

6873c6f... by Andres Rodriguez on 2018-10-15

Expose prometheus stats

02d1005... by Andres Rodriguez on 2018-10-15

Update tests

14deeef... by Andres Rodriguez on 2018-10-15

Fix format

Unmerged commits

14deeef... by Andres Rodriguez on 2018-10-15

Fix format

02d1005... by Andres Rodriguez on 2018-10-15

Update tests

6873c6f... by Andres Rodriguez on 2018-10-15

Expose prometheus stats

1aea499... by Andres Rodriguez on 2018-10-15

Fix lint

60a99f1... by Andres Rodriguez on 2018-10-15

Fixes

b82be99... by Andres Rodriguez on 2018-10-03

Minor fixes

ade2444... by Andres Rodriguez on 2018-10-03

Fix format

9bb61e6... by Andres Rodriguez on 2018-10-03

Add a basic handler to report prometheus stats over /MAAS/metrics

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 f736de9..25cbf45 100644
--- a/src/maasserver/prometheus.py
+++ b/src/maasserver/prometheus.py
@@ -24,6 +24,7 @@ try:
         CollectorRegistry,
         Gauge,
         push_to_gateway,
+        generate_latest,
     )
     PROMETHEUS = True
 except:
@@ -31,8 +32,25 @@ except:
 
 log = LegacyLogger()
 
+from django.http import HttpResponse
 
-def push_stats_to_prometheus(maas_name, push_gateway):
+
+def prometheus_handler(request):
+    if not Config.objects.get_config('prometheus_enabled'):
+        content = (
+            "No metrics available."
+            )
+        status = 404
+    else:
+        content = generate_latest(get_stats_for_prometheus())
+        status = 200
+    response = HttpResponse(content)
+    response['Content-Type'] = "text/plain"
+    response['status'] = status
+    return response
+
+
+def get_stats_for_prometheus():
     registry = CollectorRegistry()
     stats = json.loads(get_maas_stats())
 
@@ -43,6 +61,11 @@ def push_stats_to_prometheus(maas_name, push_gateway):
     for status, machines in stats['machine_status'].items():
         counter.labels(status).set(machines)
 
+    return registry
+
+
+def push_stats_to_prometheus(maas_name, push_gateway):
+    registry = get_stats_for_prometheus()
     push_to_gateway(
         push_gateway, job='stats_for_%s' % maas_name, registry=registry)
 
diff --git a/src/maasserver/tests/test_prometheus.py b/src/maasserver/tests/test_prometheus.py
index 27dc7f4..66c1af6 100644
--- a/src/maasserver/tests/test_prometheus.py
+++ b/src/maasserver/tests/test_prometheus.py
@@ -5,10 +5,15 @@
 
 __all__ = []
 
+import json
+
 from django.db import transaction
 from maasserver import prometheus
 from maasserver.models import Config
-from maasserver.prometheus import push_stats_to_prometheus
+from maasserver.prometheus import (
+    get_stats_for_prometheus,
+    push_stats_to_prometheus,
+)
 from maasserver.testing.factory import factory
 from maasserver.testing.testcase import (
     MAASServerTestCase,
@@ -28,6 +33,20 @@ from twisted.internet.defer import fail
 
 class TestPrometheus(MAASServerTestCase):
 
+    def test_get_stats_for_prometheus(self):
+        self.patch(prometheus, "CollectorRegistry")
+        self.patch(prometheus, "Gauge")
+        values = {
+            "machine_status": {
+                "random_status": 0,
+            },
+        }
+        mock = self.patch(prometheus, "get_maas_stats")
+        mock.return_value = json.dumps(values)
+        get_stats_for_prometheus()
+        self.assertThat(
+            mock, MockCalledOnce())
+
     def test_push_stats_to_prometheus(self):
         factory.make_RegionRackController()
         maas_name = 'random.maas'
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'),