diff --git a/synapse/metrics/__init__.py b/synapse/metrics/__init__.py
index 2ed82b04a5..2666f982a6 100644
--- a/synapse/metrics/__init__.py
+++ b/synapse/metrics/__init__.py
@@ -23,7 +23,7 @@ from twisted.internet import reactor
from .metric import (
CounterMetric, CallbackMetric, DistributionMetric, CacheMetric,
- MemoryUsageMetric,
+ MemoryUsageMetric, GaugeMetric,
)
from .process_collector import register_process_collector
@@ -65,6 +65,13 @@ class Metrics(object):
"""
return self._register(CounterMetric, *args, **kwargs)
+ def register_gauge(self, *args, **kwargs):
+ """
+ Returns:
+ GaugeMetric
+ """
+ return self._register(GaugeMetric, *args, **kwargs)
+
def register_callback(self, *args, **kwargs):
"""
Returns:
diff --git a/synapse/metrics/metric.py b/synapse/metrics/metric.py
index ff5aa8c0e1..9ebf2d6fdb 100644
--- a/synapse/metrics/metric.py
+++ b/synapse/metrics/metric.py
@@ -145,6 +145,36 @@ class CounterMetric(BaseMetric):
)
+class GaugeMetric(BaseMetric):
+ """A metric that can go up or down
+ """
+
+ def __init__(self, *args, **kwargs):
+ super(GaugeMetric, self).__init__(*args, **kwargs)
+
+ # dict[list[str]]: value for each set of label values. the keys are the
+ # label values, in the same order as the labels in self.labels.
+ #
+ # (if the metric is a scalar, the (single) key is the empty list).
+ self.guages = {}
+
+ def set(self, v, *values):
+ if len(values) != self.dimension():
+ raise ValueError(
+ "Expected as many values to inc() as labels (%d)" % (self.dimension())
+ )
+
+ # TODO: should assert that the tag values are all strings
+
+ self.guages[values] = v
+
+ def render(self):
+ return flatten(
+ self._render_for_labels(k, self.guages[k])
+ for k in sorted(self.guages.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
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