diff --git a/synapse/metrics/__init__.py b/synapse/metrics/__init__.py
index d5c30bbe41..d7584fc0bc 100644
--- a/synapse/metrics/__init__.py
+++ b/synapse/metrics/__init__.py
@@ -13,7 +13,7 @@
# See the License for the specific language governing permissions and
# limitations under the License.
-from .metric import CounterMetric, CacheCounterMetric
+from .metric import CounterMetric, CallbackMetric, CacheCounterMetric
# We'll keep all the available metrics in a single toplevel dict, one shared
@@ -43,6 +43,15 @@ class Metrics(object):
return metric
+ def register_callback(self, name, callback, *args, **kwargs):
+ full_name = "%s.%s" % (self.name_prefix, name)
+
+ metric = CallbackMetric(full_name, *args, callback=callback, **kwargs)
+
+ self._register(metric)
+
+ return metric
+
def register_cachecounter(self, name, *args, **kwargs):
full_name = "%s.%s" % (self.name_prefix, name)
diff --git a/synapse/metrics/metric.py b/synapse/metrics/metric.py
index 00b149f6f6..8a497fc154 100644
--- a/synapse/metrics/metric.py
+++ b/synapse/metrics/metric.py
@@ -62,6 +62,20 @@ class CounterMetric(BaseMetric):
for k in sorted(self.counts.keys())]
+class CallbackMetric(BaseMetric):
+ """A metric that returns the numeric value returned by a callback whenever
+ it is rendered. Typically this is used to implement gauges that yield the
+ size or other state of some in-memory object by actively querying it."""
+
+ def __init__(self, name, callback, keys=[]):
+ super(CallbackMetric, self).__init__(name, keys=keys)
+
+ self.callback = callback
+
+ def render(self):
+ # TODO(paul): work out something we can do with keys and vectors
+ return ["%s %d" % (self.name, self.callback())]
+
class CacheCounterMetric(object):
"""A combination of two CounterMetrics, one to count cache hits and one to
count misses.
diff --git a/tests/metrics/test_metric.py b/tests/metrics/test_metric.py
index 93e8e27e4f..b7bb375ce0 100644
--- a/tests/metrics/test_metric.py
+++ b/tests/metrics/test_metric.py
@@ -15,7 +15,9 @@
from tests import unittest
-from synapse.metrics.metric import CounterMetric, CacheCounterMetric
+from synapse.metrics.metric import (
+ CounterMetric, CallbackMetric, CacheCounterMetric
+)
class CounterMetricTestCase(unittest.TestCase):
@@ -61,6 +63,24 @@ class CounterMetricTestCase(unittest.TestCase):
])
+class CallbackMetricTestCase(unittest.TestCase):
+
+ def test_callback(self):
+ d = dict()
+
+ metric = CallbackMetric("size", lambda: len(d))
+
+ self.assertEquals(metric.render(), [
+ "size 0",
+ ])
+
+ d["key"] = "value"
+
+ self.assertEquals(metric.render(), [
+ "size 1",
+ ])
+
+
class CacheCounterMetricTestCase(unittest.TestCase):
def test_cachecounter(self):
|
