diff --git a/synapse/metrics/__init__.py b/synapse/metrics/__init__.py
index a1f7ca3449..b8d2a8e8a9 100644
--- a/synapse/metrics/__init__.py
+++ b/synapse/metrics/__init__.py
@@ -15,6 +15,7 @@
import functools
import gc
+import itertools
import logging
import os
import platform
@@ -27,8 +28,8 @@ from prometheus_client import Counter, Gauge, Histogram
from prometheus_client.core import (
REGISTRY,
CounterMetricFamily,
+ GaugeHistogramMetricFamily,
GaugeMetricFamily,
- HistogramMetricFamily,
)
from twisted.internet import reactor
@@ -46,7 +47,7 @@ logger = logging.getLogger(__name__)
METRICS_PREFIX = "/_synapse/metrics"
running_on_pypy = platform.python_implementation() == "PyPy"
-all_gauges = {} # type: Dict[str, Union[LaterGauge, InFlightGauge, BucketCollector]]
+all_gauges = {} # type: Dict[str, Union[LaterGauge, InFlightGauge]]
HAVE_PROC_SELF_STAT = os.path.exists("/proc/self/stat")
@@ -205,63 +206,83 @@ class InFlightGauge:
all_gauges[self.name] = self
-@attr.s(slots=True, hash=True)
-class BucketCollector:
- """
- Like a Histogram, but allows buckets to be point-in-time instead of
- incrementally added to.
+class GaugeBucketCollector:
+ """Like a Histogram, but the buckets are Gauges which are updated atomically.
- Args:
- name (str): Base name of metric to be exported to Prometheus.
- data_collector (callable -> dict): A synchronous callable that
- returns a dict mapping bucket to number of items in the
- bucket. If these buckets are not the same as the buckets
- given to this class, they will be remapped into them.
- buckets (list[float]): List of floats/ints of the buckets to
- give to Prometheus. +Inf is ignored, if given.
+ The data is updated by calling `update_data` with an iterable of measurements.
+ We assume that the data is updated less frequently than it is reported to
+ Prometheus, and optimise for that case.
"""
- name = attr.ib()
- data_collector = attr.ib()
- buckets = attr.ib()
+ __slots__ = ("_name", "_documentation", "_bucket_bounds", "_metric")
- def collect(self):
+ def __init__(
+ self,
+ name: str,
+ documentation: str,
+ buckets: Iterable[float],
+ registry=REGISTRY,
+ ):
+ """
+ Args:
+ name: base name of metric to be exported to Prometheus. (a _bucket suffix
+ will be added.)
+ documentation: help text for the metric
+ buckets: The top bounds of the buckets to report
+ registry: metric registry to register with
+ """
+ self._name = name
+ self._documentation = documentation
- # Fetch the data -- this must be synchronous!
- data = self.data_collector()
+ # the tops of the buckets
+ self._bucket_bounds = [float(b) for b in buckets]
+ if self._bucket_bounds != sorted(self._bucket_bounds):
+ raise ValueError("Buckets not in sorted order")
- buckets = {} # type: Dict[float, int]
+ if self._bucket_bounds[-1] != float("inf"):
+ self._bucket_bounds.append(float("inf"))
- res = []
- for x in data.keys():
- for i, bound in enumerate(self.buckets):
- if x <= bound:
- buckets[bound] = buckets.get(bound, 0) + data[x]
+ self._metric = self._values_to_metric([])
+ registry.register(self)
- for i in self.buckets:
- res.append([str(i), buckets.get(i, 0)])
+ def collect(self):
+ yield self._metric
- res.append(["+Inf", sum(data.values())])
+ def update_data(self, values: Iterable[float]):
+ """Update the data to be reported by the metric
- metric = HistogramMetricFamily(
- self.name, "", buckets=res, sum_value=sum(x * y for x, y in data.items())
+ The existing data is cleared, and each measurement in the input is assigned
+ to the relevant bucket.
+ """
+ self._metric = self._values_to_metric(values)
+
+ def _values_to_metric(self, values: Iterable[float]) -> GaugeHistogramMetricFamily:
+ total = 0.0
+ bucket_values = [0 for _ in self._bucket_bounds]
+
+ for v in values:
+ # assign each value to a bucket
+ for i, bound in enumerate(self._bucket_bounds):
+ if v <= bound:
+ bucket_values[i] += 1
+ break
+
+ # ... and increment the sum
+ total += v
+
+ # now, aggregate the bucket values so that they count the number of entries in
+ # that bucket or below.
+ accumulated_values = itertools.accumulate(bucket_values)
+
+ return GaugeHistogramMetricFamily(
+ self._name,
+ self._documentation,
+ buckets=list(
+ zip((str(b) for b in self._bucket_bounds), accumulated_values)
+ ),
+ gsum_value=total,
)
- yield metric
-
- def __attrs_post_init__(self):
- self.buckets = [float(x) for x in self.buckets if x != "+Inf"]
- if self.buckets != sorted(self.buckets):
- raise ValueError("Buckets not sorted")
-
- self.buckets = tuple(self.buckets)
-
- if self.name in all_gauges.keys():
- logger.warning("%s already registered, reregistering" % (self.name,))
- REGISTRY.unregister(all_gauges.pop(self.name))
-
- REGISTRY.register(self)
- all_gauges[self.name] = self
#
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