An initial implementation of a 'metrics' instance, similar to a 'logger' for keeping counter stats on method calls

synapse/metrics/__init__.py

@@ -0,0 +1,69 @@
+# -*- 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 .metric import CounterMetric
+
+
+# We'll keep all the available metrics in a single toplevel dict, one shared
+# for the entire process. We don't currently support per-HomeServer instances
+# of metrics, because in practice any one python VM will host only one
+# HomeServer anyway. This makes a lot of implementation neater
+all_metrics = {}
+
+
+class Metrics(object):
+    """ A single Metrics object gives a (mutable) slice view of the all_metrics
+    dict, allowing callers to easily register new metrics that are namespaced
+    nicely."""
+
+    def __init__(self, name):
+        self.name_prefix = name
+
+    def _register(self, metric):
+        all_metrics[metric.name] = metric
+
+    def register_counter(self, name, *args, **kwargs):
+        full_name = "%s.%s" % (self.name_prefix, name)
+
+        metric = CounterMetric(full_name, *args, **kwargs)
+
+        self._register(metric)
+
+        return metric
+
+    def counted(self, func):
+        """ A method decorator that registers a counter, to count invocations
+        of this method. """
+        counter = self.register_counter(func.__name__)
+
+        def wrapped(*args, **kwargs):
+            counter.inc()
+            return func(*args, **kwargs)
+        return wrapped
+
+
+def get_metrics_for(name):
+    """ Returns a Metrics instance for conveniently creating metrics
+    namespaced with the given name prefix. """
+    return Metrics(name)
+
+
+def render_all():
+    strs = []
+
+    for name in sorted(all_metrics.keys()):
+        strs += all_metrics[name].render()
+
+    return "\n".join(strs)