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# Copyright 2015-2019 Prometheus Python Client Developers
# Copyright 2019 Matrix.org Foundation C.I.C.
#
# 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.
"""
This code is based off `prometheus_client/exposition.py` from version 0.7.1.
Due to the renaming of metrics in prometheus_client 0.4.0, this customised
vendoring of the code will emit both the old versions that Synapse dashboards
expect, and the newer "best practice" version of the up-to-date official client.
"""
import math
import threading
from http.server import BaseHTTPRequestHandler, HTTPServer
from socketserver import ThreadingMixIn
from typing import Any, Dict, List, Type, Union
from urllib.parse import parse_qs, urlparse
from prometheus_client import REGISTRY, CollectorRegistry
from prometheus_client.core import Sample
from twisted.web.resource import Resource
from twisted.web.server import Request
from synapse.util import caches
CONTENT_TYPE_LATEST = "text/plain; version=0.0.4; charset=utf-8"
def floatToGoString(d: Union[int, float]) -> str:
d = float(d)
if d == math.inf:
return "+Inf"
elif d == -math.inf:
return "-Inf"
elif math.isnan(d):
return "NaN"
else:
s = repr(d)
dot = s.find(".")
# Go switches to exponents sooner than Python.
# We only need to care about positive values for le/quantile.
if d > 0 and dot > 6:
mantissa = f"{s[0]}.{s[1:dot]}{s[dot + 1 :]}".rstrip("0.")
return f"{mantissa}e+0{dot - 1}"
return s
def sample_line(line: Sample, name: str) -> str:
if line.labels:
labelstr = "{{{0}}}".format(
",".join(
[
'{}="{}"'.format(
k,
v.replace("\\", r"\\").replace("\n", r"\n").replace('"', r"\""),
)
for k, v in sorted(line.labels.items())
]
)
)
else:
labelstr = ""
timestamp = ""
if line.timestamp is not None:
# Convert to milliseconds.
timestamp = f" {int(float(line.timestamp) * 1000):d}"
return "{}{} {}{}\n".format(name, labelstr, floatToGoString(line.value), timestamp)
def generate_latest(registry: CollectorRegistry, emit_help: bool = False) -> bytes:
# Trigger the cache metrics to be rescraped, which updates the common
# metrics but do not produce metrics themselves
for collector in caches.collectors_by_name.values():
collector.collect()
output = []
for metric in registry.collect():
if not metric.samples:
# No samples, don't bother.
continue
mname = metric.name
mnewname = metric.name
mtype = metric.type
# OpenMetrics -> Prometheus
if mtype == "counter":
mnewname = mnewname + "_total"
elif mtype == "info":
mtype = "gauge"
mnewname = mnewname + "_info"
elif mtype == "stateset":
mtype = "gauge"
elif mtype == "gaugehistogram":
mtype = "histogram"
elif mtype == "unknown":
mtype = "untyped"
# Output in the old format for compatibility.
if emit_help:
output.append(
"# HELP {} {}\n".format(
mname,
metric.documentation.replace("\\", r"\\").replace("\n", r"\n"),
)
)
output.append(f"# TYPE {mname} {mtype}\n")
om_samples: Dict[str, List[str]] = {}
for s in metric.samples:
for suffix in ["_created", "_gsum", "_gcount"]:
if s.name == metric.name + suffix:
# OpenMetrics specific sample, put in a gauge at the end.
# (these come from gaugehistograms which don't get renamed,
# so no need to faff with mnewname)
om_samples.setdefault(suffix, []).append(sample_line(s, s.name))
break
else:
newname = s.name.replace(mnewname, mname)
if ":" in newname and newname.endswith("_total"):
newname = newname[: -len("_total")]
output.append(sample_line(s, newname))
for suffix, lines in sorted(om_samples.items()):
if emit_help:
output.append(
"# HELP {}{} {}\n".format(
metric.name,
suffix,
metric.documentation.replace("\\", r"\\").replace("\n", r"\n"),
)
)
output.append(f"# TYPE {metric.name}{suffix} gauge\n")
output.extend(lines)
# Get rid of the weird colon things while we're at it
if mtype == "counter":
mnewname = mnewname.replace(":total", "")
mnewname = mnewname.replace(":", "_")
if mname == mnewname:
continue
# Also output in the new format, if it's different.
if emit_help:
output.append(
"# HELP {} {}\n".format(
mnewname,
metric.documentation.replace("\\", r"\\").replace("\n", r"\n"),
)
)
output.append(f"# TYPE {mnewname} {mtype}\n")
for s in metric.samples:
# Get rid of the OpenMetrics specific samples (we should already have
# dealt with them above anyway.)
for suffix in ["_created", "_gsum", "_gcount"]:
if s.name == metric.name + suffix:
break
else:
output.append(
sample_line(s, s.name.replace(":total", "").replace(":", "_"))
)
return "".join(output).encode("utf-8")
class MetricsHandler(BaseHTTPRequestHandler):
"""HTTP handler that gives metrics from ``REGISTRY``."""
registry = REGISTRY
def do_GET(self) -> None:
registry = self.registry
params = parse_qs(urlparse(self.path).query)
if "help" in params:
emit_help = True
else:
emit_help = False
try:
output = generate_latest(registry, emit_help=emit_help)
except Exception:
self.send_error(500, "error generating metric output")
raise
self.send_response(200)
self.send_header("Content-Type", CONTENT_TYPE_LATEST)
self.send_header("Content-Length", str(len(output)))
self.end_headers()
self.wfile.write(output)
def log_message(self, format: str, *args: Any) -> None:
"""Log nothing."""
@classmethod
def factory(cls, registry: CollectorRegistry) -> Type:
"""Returns a dynamic MetricsHandler class tied
to the passed registry.
"""
# This implementation relies on MetricsHandler.registry
# (defined above and defaulted to REGISTRY).
# As we have unicode_literals, we need to create a str()
# object for type().
cls_name = str(cls.__name__)
MyMetricsHandler = type(cls_name, (cls, object), {"registry": registry})
return MyMetricsHandler
class _ThreadingSimpleServer(ThreadingMixIn, HTTPServer):
"""Thread per request HTTP server."""
# Make worker threads "fire and forget". Beginning with Python 3.7 this
# prevents a memory leak because ``ThreadingMixIn`` starts to gather all
# non-daemon threads in a list in order to join on them at server close.
# Enabling daemon threads virtually makes ``_ThreadingSimpleServer`` the
# same as Python 3.7's ``ThreadingHTTPServer``.
daemon_threads = True
def start_http_server(
port: int, addr: str = "", registry: CollectorRegistry = REGISTRY
) -> None:
"""Starts an HTTP server for prometheus metrics as a daemon thread"""
CustomMetricsHandler = MetricsHandler.factory(registry)
httpd = _ThreadingSimpleServer((addr, port), CustomMetricsHandler)
t = threading.Thread(target=httpd.serve_forever)
t.daemon = True
t.start()
class MetricsResource(Resource):
"""
Twisted ``Resource`` that serves prometheus metrics.
"""
isLeaf = True
def __init__(self, registry: CollectorRegistry = REGISTRY):
self.registry = registry
def render_GET(self, request: Request) -> bytes:
request.setHeader(b"Content-Type", CONTENT_TYPE_LATEST.encode("ascii"))
response = generate_latest(self.registry)
request.setHeader(b"Content-Length", str(len(response)))
return response
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