Prometheus exporter support for auto instrumentation (#3413)

CHANGELOG.md

@@ -21,6 +21,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#3251](https://github.com/open-telemetry/opentelemetry-python/pull/3251))
 - Add missing schema_url in global api for logging and metrics
   ([#3251](https://github.com/open-telemetry/opentelemetry-python/pull/3251))
+- Prometheus exporter support for auto instrumentation 
+  ([#3413](https://github.com/open-telemetry/opentelemetry-python/pull/3413))
+
 
 ## Version 1.20.0/0.41b0 (2023-09-04)
 

exporter/opentelemetry-exporter-prometheus/pyproject.toml

@@ -26,15 +26,16 @@ classifiers = [
 ]
 dependencies = [
   "opentelemetry-api ~= 1.12",
-  "opentelemetry-sdk ~= 1.12",
+  # DONOTMERGE: confirm that this will becomes ~= 1.21 in the next release
+  "opentelemetry-sdk ~= 1.21.0.dev",
   "prometheus_client >= 0.5.0, < 1.0.0",
 ]
 
 [project.optional-dependencies]
 test = []
 
-[project.entry-points.opentelemetry_metric_reader]
-prometheus = "opentelemetry.exporter.prometheus:PrometheusMetricReader"
+[project.entry-points.opentelemetry_metrics_exporter]
+prometheus = "opentelemetry.exporter.prometheus:_AutoPrometheusMetricReader"
 
 [project.urls]
 Homepage = "https://github.com/open-telemetry/opentelemetry-python/tree/main/exporter/opentelemetry-exporter-prometheus"

exporter/opentelemetry-exporter-prometheus/src/opentelemetry/exporter/prometheus/__init__.py

@@ -66,9 +66,11 @@
 from itertools import chain
 from json import dumps
 from logging import getLogger
+from os import environ
 from re import IGNORECASE, UNICODE, compile
 from typing import Dict, Sequence, Tuple, Union
 
+from prometheus_client import start_http_server
 from prometheus_client.core import (
     REGISTRY,
     CounterMetricFamily,
@@ -78,6 +80,10 @@
 )
 from prometheus_client.core import Metric as PrometheusMetric
 
+from opentelemetry.sdk.environment_variables import (
+    OTEL_EXPORTER_PROMETHEUS_HOST,
+    OTEL_EXPORTER_PROMETHEUS_PORT,
+)
 from opentelemetry.sdk.metrics import Counter
 from opentelemetry.sdk.metrics import Histogram as HistogramInstrument
 from opentelemetry.sdk.metrics import (
@@ -375,3 +381,21 @@ def _create_info_metric(
         info = InfoMetricFamily(name, description, labels=attributes)
         info.add_metric(labels=list(attributes.keys()), value=attributes)
         return info
+
+
+class _AutoPrometheusMetricReader(PrometheusMetricReader):
+    """Thin wrapper around PrometheusMetricReader used for the opentelemetry_metrics_exporter entry point.
+
+    This allows users to use the prometheus exporter with opentelemetry-instrument. It handles
+    starting the Prometheus http server on the the correct port and host.
+    """
+
+    def __init__(self) -> None:
+        super().__init__()
+
+        # Default values are specified in
+        # https://github.com/open-telemetry/opentelemetry-specification/blob/v1.24.0/specification/configuration/sdk-environment-variables.md#prometheus-exporter
+        start_http_server(
+            port=int(environ.get(OTEL_EXPORTER_PROMETHEUS_PORT, "9464")),
+            addr=environ.get(OTEL_EXPORTER_PROMETHEUS_HOST, "localhost"),
+        )

exporter/opentelemetry-exporter-prometheus/tests/test_entrypoints.py

@@ -0,0 +1,75 @@
+# 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.
+
+# pylint: disable=no-self-use
+
+import os
+from unittest import TestCase
+from unittest.mock import ANY, Mock, patch
+
+from opentelemetry.exporter.prometheus import _AutoPrometheusMetricReader
+from opentelemetry.sdk._configuration import _import_exporters
+from opentelemetry.sdk.environment_variables import (
+    OTEL_EXPORTER_PROMETHEUS_HOST,
+    OTEL_EXPORTER_PROMETHEUS_PORT,
+)
+
+
+class TestEntrypoints(TestCase):
+    def test_import_exporters(self) -> None:
+        """
+        Tests that the entrypoint can be loaded and doesn't have a typo in the name
+        """
+        (
+            _trace_exporters,
+            metric_exporters,
+            _logs_exporters,
+        ) = _import_exporters(
+            trace_exporter_names=[],
+            metric_exporter_names=["prometheus"],
+            log_exporter_names=[],
+        )
+
+        self.assertIs(
+            metric_exporters["prometheus"],
+            _AutoPrometheusMetricReader,
+        )
+
+    @patch("opentelemetry.exporter.prometheus.start_http_server")
+    @patch.dict(os.environ)
+    def test_starts_http_server_defaults(
+        self, mock_start_http_server: Mock
+    ) -> None:
+        _AutoPrometheusMetricReader()
+        mock_start_http_server.assert_called_once_with(
+            port=9464, addr="localhost"
+        )
+
+    @patch("opentelemetry.exporter.prometheus.start_http_server")
+    @patch.dict(os.environ, {OTEL_EXPORTER_PROMETHEUS_HOST: "1.2.3.4"})
+    def test_starts_http_server_host_envvar(
+        self, mock_start_http_server: Mock
+    ) -> None:
+        _AutoPrometheusMetricReader()
+        mock_start_http_server.assert_called_once_with(
+            port=ANY, addr="1.2.3.4"
+        )
+
+    @patch("opentelemetry.exporter.prometheus.start_http_server")
+    @patch.dict(os.environ, {OTEL_EXPORTER_PROMETHEUS_PORT: "9999"})
+    def test_starts_http_server_port_envvar(
+        self, mock_start_http_server: Mock
+    ) -> None:
+        _AutoPrometheusMetricReader()
+        mock_start_http_server.assert_called_once_with(port=9999, addr=ANY)

opentelemetry-sdk/src/opentelemetry/sdk/environment_variables.py

@@ -678,3 +678,27 @@
 experimental feature and the name of this variable and its behavior can change
 in a non-backwards compatible way.
 """
+
+OTEL_EXPORTER_PROMETHEUS_HOST = "OTEL_EXPORTER_PROMETHEUS_HOST"
+"""
+.. envvar:: OTEL_EXPORTER_PROMETHEUS_HOST
+
+The :envvar:`OTEL_EXPORTER_PROMETHEUS_HOST` environment variable configures the host used by
+the Prometheus exporter.
+Default: "localhost"
+
+This is an experimental environment variable and the name of this variable and its behavior can
+change in a non-backwards compatible way.
+"""
+
+OTEL_EXPORTER_PROMETHEUS_PORT = "OTEL_EXPORTER_PROMETHEUS_PORT"
+"""
+.. envvar:: OTEL_EXPORTER_PROMETHEUS_PORT
+
+The :envvar:`OTEL_EXPORTER_PROMETHEUS_PORT` environment variable configures the port used by
+the Prometheus exporter.
+Default: 9464
+
+This is an experimental environment variable and the name of this variable and its behavior can
+change in a non-backwards compatible way.
+"""