A trivial 'hello world'-style resource on /_synapse/metrics, with optional commandline flag

synapse/app/homeserver.py

@@ -147,6 +147,13 @@ class SynapseHomeServer(HomeServer):
         else:
             self.root_resource = Resource()
 
+        if self.get_config().enable_metrics:
+            from synapse.metrics.resource import (
+                MetricsResource, METRICS_PREFIX
+            )
+
+            desired_tree.append((METRICS_PREFIX, MetricsResource(self)))
+
         # ideally we'd just use getChild and putChild but getChild doesn't work
         # unless you give it a Request object IN ADDITION to the name :/ So
         # instead, we'll store a copy of this mapping so we can actually add

synapse/metrics/resource.py

@@ -0,0 +1,37 @@
+# -*- coding: utf-8 -*-
+# Copyright 2015 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from twisted.web.resource import Resource
+from twisted.web.server import NOT_DONE_YET
+
+
+METRICS_PREFIX = "/_synapse/metrics"
+
+
+class MetricsResource(Resource):
+    isLeaf = True
+
+    def __init__(self, hs):
+        Resource.__init__(self) # Resource is old-style, so no super()
+
+        self.hs = hs
+
+    def render_GET(self, request):
+        response = "Hello, world!"
+
+        request.setHeader("Content-Type", "text/plain")
+        request.setHeader("Content-Length", str(len(response)))
+
+        return response