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Merge pull request #8425 from matrix-org/rav/extremity_metrics
Add an improved "forward extremities" metric
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a0a1ba6973
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changelog.d/8425.feature
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changelog.d/8425.feature
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Add experimental prometheus metric to track numbers of "large" rooms for state resolutiom.
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@ -15,6 +15,7 @@
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import functools
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import gc
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import itertools
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import logging
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import os
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import platform
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@ -27,8 +28,8 @@ from prometheus_client import Counter, Gauge, Histogram
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from prometheus_client.core import (
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REGISTRY,
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CounterMetricFamily,
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GaugeHistogramMetricFamily,
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GaugeMetricFamily,
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HistogramMetricFamily,
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)
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from twisted.internet import reactor
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@ -46,7 +47,7 @@ logger = logging.getLogger(__name__)
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METRICS_PREFIX = "/_synapse/metrics"
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running_on_pypy = platform.python_implementation() == "PyPy"
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all_gauges = {} # type: Dict[str, Union[LaterGauge, InFlightGauge, BucketCollector]]
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all_gauges = {} # type: Dict[str, Union[LaterGauge, InFlightGauge]]
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HAVE_PROC_SELF_STAT = os.path.exists("/proc/self/stat")
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@ -205,63 +206,83 @@ class InFlightGauge:
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all_gauges[self.name] = self
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@attr.s(slots=True, hash=True)
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class BucketCollector:
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"""
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Like a Histogram, but allows buckets to be point-in-time instead of
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incrementally added to.
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class GaugeBucketCollector:
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"""Like a Histogram, but the buckets are Gauges which are updated atomically.
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Args:
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name (str): Base name of metric to be exported to Prometheus.
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data_collector (callable -> dict): A synchronous callable that
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returns a dict mapping bucket to number of items in the
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bucket. If these buckets are not the same as the buckets
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given to this class, they will be remapped into them.
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buckets (list[float]): List of floats/ints of the buckets to
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give to Prometheus. +Inf is ignored, if given.
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The data is updated by calling `update_data` with an iterable of measurements.
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We assume that the data is updated less frequently than it is reported to
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Prometheus, and optimise for that case.
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"""
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name = attr.ib()
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data_collector = attr.ib()
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buckets = attr.ib()
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__slots__ = ("_name", "_documentation", "_bucket_bounds", "_metric")
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def __init__(
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self,
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name: str,
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documentation: str,
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buckets: Iterable[float],
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registry=REGISTRY,
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):
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"""
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Args:
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name: base name of metric to be exported to Prometheus. (a _bucket suffix
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will be added.)
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documentation: help text for the metric
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buckets: The top bounds of the buckets to report
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registry: metric registry to register with
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"""
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self._name = name
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self._documentation = documentation
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# the tops of the buckets
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self._bucket_bounds = [float(b) for b in buckets]
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if self._bucket_bounds != sorted(self._bucket_bounds):
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raise ValueError("Buckets not in sorted order")
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if self._bucket_bounds[-1] != float("inf"):
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self._bucket_bounds.append(float("inf"))
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self._metric = self._values_to_metric([])
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registry.register(self)
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def collect(self):
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yield self._metric
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# Fetch the data -- this must be synchronous!
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data = self.data_collector()
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def update_data(self, values: Iterable[float]):
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"""Update the data to be reported by the metric
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buckets = {} # type: Dict[float, int]
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The existing data is cleared, and each measurement in the input is assigned
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to the relevant bucket.
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"""
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self._metric = self._values_to_metric(values)
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res = []
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for x in data.keys():
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for i, bound in enumerate(self.buckets):
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if x <= bound:
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buckets[bound] = buckets.get(bound, 0) + data[x]
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def _values_to_metric(self, values: Iterable[float]) -> GaugeHistogramMetricFamily:
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total = 0.0
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bucket_values = [0 for _ in self._bucket_bounds]
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for i in self.buckets:
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res.append([str(i), buckets.get(i, 0)])
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for v in values:
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# assign each value to a bucket
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for i, bound in enumerate(self._bucket_bounds):
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if v <= bound:
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bucket_values[i] += 1
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break
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res.append(["+Inf", sum(data.values())])
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# ... and increment the sum
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total += v
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metric = HistogramMetricFamily(
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self.name, "", buckets=res, sum_value=sum(x * y for x, y in data.items())
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# now, aggregate the bucket values so that they count the number of entries in
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# that bucket or below.
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accumulated_values = itertools.accumulate(bucket_values)
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return GaugeHistogramMetricFamily(
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self._name,
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self._documentation,
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buckets=list(
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zip((str(b) for b in self._bucket_bounds), accumulated_values)
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),
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gsum_value=total,
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)
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yield metric
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def __attrs_post_init__(self):
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self.buckets = [float(x) for x in self.buckets if x != "+Inf"]
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if self.buckets != sorted(self.buckets):
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raise ValueError("Buckets not sorted")
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self.buckets = tuple(self.buckets)
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if self.name in all_gauges.keys():
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logger.warning("%s already registered, reregistering" % (self.name,))
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REGISTRY.unregister(all_gauges.pop(self.name))
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REGISTRY.register(self)
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all_gauges[self.name] = self
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#
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@ -26,6 +26,7 @@ import math
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import threading
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from http.server import BaseHTTPRequestHandler, HTTPServer
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from socketserver import ThreadingMixIn
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from typing import Dict, List
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from urllib.parse import parse_qs, urlparse
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from prometheus_client import REGISTRY
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@ -124,16 +125,33 @@ def generate_latest(registry, emit_help=False):
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)
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)
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output.append("# TYPE {0} {1}\n".format(mname, mtype))
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for sample in metric.samples:
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# Get rid of the OpenMetrics specific samples
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om_samples = {} # type: Dict[str, List[str]]
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for s in metric.samples:
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for suffix in ["_created", "_gsum", "_gcount"]:
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if sample.name.endswith(suffix):
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if s.name == metric.name + suffix:
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# OpenMetrics specific sample, put in a gauge at the end.
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# (these come from gaugehistograms which don't get renamed,
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# so no need to faff with mnewname)
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om_samples.setdefault(suffix, []).append(sample_line(s, s.name))
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break
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else:
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newname = sample.name.replace(mnewname, mname)
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newname = s.name.replace(mnewname, mname)
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if ":" in newname and newname.endswith("_total"):
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newname = newname[: -len("_total")]
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output.append(sample_line(sample, newname))
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output.append(sample_line(s, newname))
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for suffix, lines in sorted(om_samples.items()):
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if emit_help:
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output.append(
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"# HELP {0}{1} {2}\n".format(
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metric.name,
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suffix,
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metric.documentation.replace("\\", r"\\").replace("\n", r"\n"),
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)
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)
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output.append("# TYPE {0}{1} gauge\n".format(metric.name, suffix))
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output.extend(lines)
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# Get rid of the weird colon things while we're at it
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if mtype == "counter":
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@ -152,16 +170,16 @@ def generate_latest(registry, emit_help=False):
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)
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)
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output.append("# TYPE {0} {1}\n".format(mnewname, mtype))
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for sample in metric.samples:
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# Get rid of the OpenMetrics specific samples
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for s in metric.samples:
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# Get rid of the OpenMetrics specific samples (we should already have
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# dealt with them above anyway.)
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for suffix in ["_created", "_gsum", "_gcount"]:
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if sample.name.endswith(suffix):
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if s.name == metric.name + suffix:
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break
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else:
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output.append(
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sample_line(
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sample, sample.name.replace(":total", "").replace(":", "_")
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)
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sample_line(s, s.name.replace(":total", "").replace(":", "_"))
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)
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return "".join(output).encode("utf-8")
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@ -12,10 +12,8 @@
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import typing
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from collections import Counter
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from synapse.metrics import BucketCollector
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from synapse.metrics import GaugeBucketCollector
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from synapse.metrics.background_process_metrics import run_as_background_process
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from synapse.storage._base import SQLBaseStore
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from synapse.storage.database import DatabasePool
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@ -23,6 +21,26 @@ from synapse.storage.databases.main.event_push_actions import (
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EventPushActionsWorkerStore,
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)
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# Collect metrics on the number of forward extremities that exist.
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_extremities_collecter = GaugeBucketCollector(
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"synapse_forward_extremities",
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"Number of rooms on the server with the given number of forward extremities"
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" or fewer",
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buckets=[1, 2, 3, 5, 7, 10, 15, 20, 50, 100, 200, 500],
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)
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# we also expose metrics on the "number of excess extremity events", which is
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# (E-1)*N, where E is the number of extremities and N is the number of state
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# events in the room. This is an approximation to the number of state events
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# we could remove from state resolution by reducing the graph to a single
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# forward extremity.
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_excess_state_events_collecter = GaugeBucketCollector(
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"synapse_excess_extremity_events",
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"Number of rooms on the server with the given number of excess extremity "
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"events, or fewer",
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buckets=[0] + [1 << n for n in range(12)],
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)
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class ServerMetricsStore(EventPushActionsWorkerStore, SQLBaseStore):
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"""Functions to pull various metrics from the DB, for e.g. phone home
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@ -32,18 +50,6 @@ class ServerMetricsStore(EventPushActionsWorkerStore, SQLBaseStore):
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def __init__(self, database: DatabasePool, db_conn, hs):
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super().__init__(database, db_conn, hs)
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# Collect metrics on the number of forward extremities that exist.
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# Counter of number of extremities to count
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self._current_forward_extremities_amount = (
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Counter()
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) # type: typing.Counter[int]
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BucketCollector(
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"synapse_forward_extremities",
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lambda: self._current_forward_extremities_amount,
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buckets=[1, 2, 3, 5, 7, 10, 15, 20, 50, 100, 200, 500, "+Inf"],
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)
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# Read the extrems every 60 minutes
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def read_forward_extremities():
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# run as a background process to make sure that the database transactions
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@ -58,14 +64,25 @@ class ServerMetricsStore(EventPushActionsWorkerStore, SQLBaseStore):
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def fetch(txn):
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txn.execute(
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"""
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select count(*) c from event_forward_extremities
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group by room_id
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SELECT t1.c, t2.c
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FROM (
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SELECT room_id, COUNT(*) c FROM event_forward_extremities
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GROUP BY room_id
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) t1 LEFT JOIN (
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SELECT room_id, COUNT(*) c FROM current_state_events
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GROUP BY room_id
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) t2 ON t1.room_id = t2.room_id
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"""
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)
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return txn.fetchall()
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res = await self.db_pool.runInteraction("read_forward_extremities", fetch)
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self._current_forward_extremities_amount = Counter([x[0] for x in res])
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_extremities_collecter.update_data(x[0] for x in res)
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_excess_state_events_collecter.update_data(
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(x[0] - 1) * x[1] for x in res if x[1]
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)
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async def count_daily_messages(self):
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"""
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@ -52,14 +52,14 @@ class ExtremStatisticsTestCase(HomeserverTestCase):
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self.reactor.advance(60 * 60 * 1000)
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self.pump(1)
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items = set(
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items = list(
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filter(
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lambda x: b"synapse_forward_extremities_" in x,
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generate_latest(REGISTRY).split(b"\n"),
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generate_latest(REGISTRY, emit_help=False).split(b"\n"),
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)
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)
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expected = {
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expected = [
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b'synapse_forward_extremities_bucket{le="1.0"} 0.0',
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b'synapse_forward_extremities_bucket{le="2.0"} 2.0',
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b'synapse_forward_extremities_bucket{le="3.0"} 2.0',
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@ -72,9 +72,12 @@ class ExtremStatisticsTestCase(HomeserverTestCase):
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b'synapse_forward_extremities_bucket{le="100.0"} 3.0',
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b'synapse_forward_extremities_bucket{le="200.0"} 3.0',
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b'synapse_forward_extremities_bucket{le="500.0"} 3.0',
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b'synapse_forward_extremities_bucket{le="+Inf"} 3.0',
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b"synapse_forward_extremities_count 3.0",
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b"synapse_forward_extremities_sum 10.0",
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}
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# per https://docs.google.com/document/d/1KwV0mAXwwbvvifBvDKH_LU1YjyXE_wxCkHNoCGq1GX0/edit#heading=h.wghdjzzh72j9,
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# "inf" is valid: "this includes variants such as inf"
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b'synapse_forward_extremities_bucket{le="inf"} 3.0',
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b"# TYPE synapse_forward_extremities_gcount gauge",
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b"synapse_forward_extremities_gcount 3.0",
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b"# TYPE synapse_forward_extremities_gsum gauge",
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b"synapse_forward_extremities_gsum 10.0",
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]
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self.assertEqual(items, expected)
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