# Copyright The OpenTelemetry Authors
#
# 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 library allows export of metrics data to `Prometheus <https://prometheus.io/>`_.
Usage
-----
The **OpenTelemetry Prometheus Exporter** allows export of `OpenTelemetry`_ metrics to `Prometheus`_.
.. _Prometheus: https://prometheus.io/
.. _OpenTelemetry: https://github.com/open-telemetry/opentelemetry-python/
.. code:: python
from opentelemetry import metrics
from opentelemetry.ext.prometheus import PrometheusMetricsExporter
from opentelemetry.sdk.metrics import Counter, Meter
from opentelemetry.sdk.metrics.export.controller import PushController
from prometheus_client import start_http_server
# Start Prometheus client
start_http_server(port=8000, addr="localhost")
# Meter is responsible for creating and recording metrics
metrics.set_meter_provider(MeterProvider())
meter = metrics.meter()
# exporter to export metrics to Prometheus
prefix = "MyAppPrefix"
exporter = PrometheusMetricsExporter(prefix)
# controller collects metrics created from meter and exports it via the
# exporter every interval
controller = PushController(meter, exporter, 5)
counter = meter.create_metric(
"requests",
"number of requests",
"requests",
int,
Counter,
("environment",),
)
# Labels are used to identify key-values that are associated with a specific
# metric that you want to record. These are useful for pre-aggregation and can
# be used to store custom dimensions pertaining to a metric
labels = {"environment": "staging"}
counter.add(25, labels)
input("Press any key to exit...")
API
---
"""
import collections
import logging
import re
from typing import Sequence
from prometheus_client import start_http_server
from prometheus_client.core import (
REGISTRY,
CollectorRegistry,
CounterMetricFamily,
UnknownMetricFamily,
)
from opentelemetry.metrics import Counter, Measure, Metric
from opentelemetry.sdk.metrics.export import (
MetricRecord,
MetricsExporter,
MetricsExportResult,
)
logger = logging.getLogger(__name__)
[docs]class PrometheusMetricsExporter(MetricsExporter):
"""Prometheus metric exporter for OpenTelemetry.
Args:
prefix: single-word application prefix relevant to the domain
the metric belongs to.
"""
def __init__(self, prefix: str = ""):
self._collector = CustomCollector(prefix)
REGISTRY.register(self._collector)
[docs] def export(
self, metric_records: Sequence[MetricRecord]
) -> MetricsExportResult:
self._collector.add_metrics_data(metric_records)
return MetricsExportResult.SUCCESS
[docs] def shutdown(self) -> None:
REGISTRY.unregister(self._collector)
[docs]class CustomCollector:
""" CustomCollector represents the Prometheus Collector object
https://github.com/prometheus/client_python#custom-collectors
"""
def __init__(self, prefix: str = ""):
self._prefix = prefix
self._metrics_to_export = collections.deque()
self._non_letters_nor_digits_re = re.compile(
r"[^\w]", re.UNICODE | re.IGNORECASE
)
[docs] def add_metrics_data(self, metric_records: Sequence[MetricRecord]):
self._metrics_to_export.append(metric_records)
[docs] def collect(self):
"""Collect fetches the metrics from OpenTelemetry
and delivers them as Prometheus Metrics.
Collect is invoked every time a prometheus.Gatherer is run
for example when the HTTP endpoint is invoked by Prometheus.
"""
while self._metrics_to_export:
for metric_record in self._metrics_to_export.popleft():
prometheus_metric = self._translate_to_prometheus(
metric_record
)
if prometheus_metric is not None:
yield prometheus_metric
def _translate_to_prometheus(self, metric_record: MetricRecord):
prometheus_metric = None
label_values = []
label_keys = []
for label_tuple in metric_record.labels:
label_keys.append(self._sanitize(label_tuple[0]))
label_values.append(label_tuple[1])
metric_name = ""
if self._prefix != "":
metric_name = self._prefix + "_"
metric_name += self._sanitize(metric_record.metric.name)
if isinstance(metric_record.metric, Counter):
prometheus_metric = CounterMetricFamily(
name=metric_name,
documentation=metric_record.metric.description,
labels=label_keys,
)
prometheus_metric.add_metric(
labels=label_values, value=metric_record.aggregator.checkpoint
)
# TODO: Add support for histograms when supported in OT
elif isinstance(metric_record.metric, Measure):
prometheus_metric = UnknownMetricFamily(
name=metric_name,
documentation=metric_record.metric.description,
labels=label_keys,
)
prometheus_metric.add_metric(
labels=label_values, value=metric_record.aggregator.checkpoint
)
else:
logger.warning(
"Unsupported metric type. %s", type(metric_record.metric)
)
return prometheus_metric
def _sanitize(self, key):
""" sanitize the given metric name or label according to Prometheus rule.
Replace all characters other than [A-Za-z0-9_] with '_'.
"""
return self._non_letters_nor_digits_re.sub("_", key)