Add a twisted resource for exposing metrics via twisted.web.

README.md

@@ -228,6 +228,24 @@ To add Prometheus exposition to an existing HTTP server, see the `MetricsServlet
 which provides a `BaseHTTPRequestHandler`. It also serves as a simple example of how
 to write a custom endpoint.
 
+#### Twisted
+
+To use prometheus with [twisted](https://twistedmatrix.com/), there is `MetricsResource` which exposes metrics as a twisted resource.
+
+```python
+from prometheus_client.twisted import MetricsResource
+from twisted.web.server import Site
+from twisted.web.resource import Resource
+from twisted.internet import reactor
+
+root = Resource()
+root.putChild(b'metrics', MetricsResource())
+
+factory = Site(root)
+reactor.listenTCP(8000, factory)
+reactor.run()
+```
+
 ### Node exporter textfile collector
 
 The [textfile collector](https://github.com/prometheus/node_exporter#textfile-collector)

prometheus_client/twisted/__init__.py

@@ -0,0 +1,3 @@
+from ._exposition import MetricsResource
+
+__all__ = ['MetricsResource']

prometheus_client/twisted/_exposition.py

@@ -0,0 +1,18 @@
+from __future__ import absolute_import, unicode_literals
+from .. import REGISTRY, generate_latest, CONTENT_TYPE_LATEST
+
+from twisted.web.resource import Resource
+
+
+class MetricsResource(Resource):
+    """
+    Twisted ``Resource`` that serves prometheus metrics.
+    """
+    isLeaf = True
+
+    def __init__(self, registry=REGISTRY):
+        self.registry = registry
+
+    def render_GET(self, request):
+        request.setHeader(b'Content-Type', CONTENT_TYPE_LATEST.encode('ascii'))
+        return generate_latest(self.registry)

setup.py

@@ -11,7 +11,10 @@
     license = "Apache Software License 2.0",
     keywords = "prometheus monitoring instrumentation client",
     url = "https://github.com/prometheus/client_python",
-    packages=['prometheus_client', 'prometheus_client.bridge'],
+    packages=['prometheus_client', 'prometheus_client.bridge', 'prometheus_client.twisted'],
+    extras_requires={
+        'twisted': ['twisted'],
+    },
     test_suite="tests",
     classifiers=[
         "Development Status :: 4 - Beta",

tests/test_twisted.py

@@ -0,0 +1,48 @@
+from __future__ import absolute_import, unicode_literals
+
+from unittest import skipUnless
+
+from prometheus_client import Counter
+from prometheus_client import CollectorRegistry, generate_latest
+
+try:
+    from prometheus_client.twisted import MetricsResource
+
+    from twisted.trial.unittest import TestCase
+    from twisted.web.server import Site
+    from twisted.web.resource import Resource
+    from twisted.internet import reactor
+    from twisted.web.client import Agent
+    from twisted.web.client import readBody
+    HAVE_TWISTED = True
+except ImportError:
+    from unittest import TestCase
+    HAVE_TWISTED = False
+
+
+class MetricsResourceTest(TestCase):
+    @skipUnless(HAVE_TWISTED, "Don't have twisted installed.")
+    def setUp(self):
+        self.registry = CollectorRegistry()
+
+    def test_reports_metrics(self):
+        """
+        ``MetricsResource`` serves the metrics from the provided registry.
+        """
+        c = Counter('cc', 'A counter', registry=self.registry)
+        c.inc()
+
+        root = Resource()
+        root.putChild(b'metrics', MetricsResource(registry=self.registry))
+        server = reactor.listenTCP(0, Site(root))
+        self.addCleanup(server.stopListening)
+
+        agent = Agent(reactor)
+        port = server.getHost().port
+        url = u"http://localhost:{port}/metrics".format(port=port)
+        d = agent.request(b"GET", url.encode("ascii"))
+
+        d.addCallback(readBody)
+        d.addCallback(self.assertEqual, generate_latest(self.registry))
+
+        return d