opentelemetry-exporter-http-transport: enable entry-point loading of transport implementations (#5320)

* opentelemetry-exporter-http-transport: enable entry-point loading of transport implementations

* add changelog fragment

* fix Python 3.10 typing import error

* fix typecheck errors

* check that returned class is a subclass of BaseHTTPTransport

* Change kwargs type hint to Any in _requests.py

* Refactor kwargs type hint to Any for urllib3

* address comments

Author: herin049

.changelog/5320.added

@@ -0,0 +1 @@
+`opentelemetry-exporter-http-transport`: enable entry-point loading of transport implementations

exporter/opentelemetry-exporter-http-transport/pyproject.toml

@@ -25,7 +25,9 @@ classifiers = [
   "Programming Language :: Python :: 3.13",
   "Programming Language :: Python :: 3.14",
 ]
-dependencies = []
+dependencies = [
+  "opentelemetry-api ~= 1.15",
+]
 
 [project.optional-dependencies]
 urllib3 = [
@@ -39,6 +41,10 @@ requests = [
 Homepage = "https://github.com/open-telemetry/opentelemetry-python/tree/main/exporter/opentelemetry-exporter-http-transport"
 Repository = "https://github.com/open-telemetry/opentelemetry-python"
 
+[project.entry-points.opentelemetry_http_transport]
+urllib3 = "opentelemetry.exporter.http.transport._urllib3:Urllib3HTTPTransport"
+requests = "opentelemetry.exporter.http.transport._requests:RequestsHTTPTransport"
+
 [tool.hatch.version]
 path = "src/opentelemetry/exporter/http/transport/version/__init__.py"
 

exporter/opentelemetry-exporter-http-transport/src/opentelemetry/exporter/http/transport/__init__.py

@@ -1,2 +1,76 @@
 # Copyright The OpenTelemetry Authors
 # SPDX-License-Identifier: Apache-2.0
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, cast
+
+# pylint: disable-next=import-error
+from opentelemetry.exporter.http.transport._requests import (
+    RequestsHTTPTransport as _RequestsHTTPTransport,
+)
+
+# pylint: disable-next=import-error
+from opentelemetry.exporter.http.transport._urllib3 import (
+    Urllib3HTTPTransport as _Urllib3HTTPTransport,
+)
+
+if TYPE_CHECKING:
+    from typing import Any, Protocol
+
+    from opentelemetry.exporter.http.transport._base import BaseHTTPTransport
+
+    class BaseHTTPTransportFactory(Protocol):
+        def __call__(
+            self,
+            *,
+            verify: bool | str,
+            cert: str | tuple[str, str] | None,
+            **kwargs: Any,
+        ) -> BaseHTTPTransport: ...
+
+
+_KNOWN_TRANSPORTS: dict[str, BaseHTTPTransportFactory] = {
+    "requests": _RequestsHTTPTransport,
+    "urllib3": _Urllib3HTTPTransport,
+}
+
+
+def _load_http_transport_factory(name: str) -> BaseHTTPTransportFactory:
+    """Return the transport factory registered under *name*.
+
+    Checks the built-in transport registry first to avoid the overhead of an
+    entry-point scan for built-in transports. Falls back to standard entry-point
+    discovery for user supplied transports registered under the
+    ``opentelemetry_http_transport`` group.
+
+    :param name: Entry point name, e.g. ``"requests"`` or ``"urllib3"``.
+    :returns: A callable with signature
+        ``(*, verify, cert, **kwargs) -> BaseHTTPTransport``.
+    :raises ValueError: If no transport is registered under *name*.
+    :raises TypeError: If the loaded entry point is not callable.
+    """
+    if name in _KNOWN_TRANSPORTS:
+        return _KNOWN_TRANSPORTS[name]
+    # pylint: disable-next=import-outside-toplevel,import-error
+    from opentelemetry.util._importlib_metadata import (  # noqa: PLC0415
+        entry_points,
+    )
+
+    ep = next(
+        iter(entry_points(group="opentelemetry_http_transport", name=name)),
+        None,
+    )
+    if not ep:
+        raise ValueError(
+            f"No HTTP transport registered under name {name!r}. "
+            "Install the corresponding extra or register an entry point "
+            "under the 'opentelemetry_http_transport' group."
+        )
+    factory = ep.load()
+    if not callable(factory):
+        raise TypeError(
+            f"Transport {name!r} loaded from entry point is not callable "
+            f"(got {factory!r})."
+        )
+    return cast("BaseHTTPTransportFactory", factory)

exporter/opentelemetry-exporter-http-transport/src/opentelemetry/exporter/http/transport/_base.py

@@ -1,11 +1,16 @@
 # Copyright The OpenTelemetry Authors
 # SPDX-License-Identifier: Apache-2.0
 
+from __future__ import annotations
+
 import json
 from abc import ABC, abstractmethod
-from collections.abc import Mapping
 from dataclasses import dataclass
-from typing import Any
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from collections.abc import Mapping
+    from typing import Any
 
 
 @dataclass(frozen=True, slots=True)

exporter/opentelemetry-exporter-http-transport/src/opentelemetry/exporter/http/transport/_requests.py

@@ -4,9 +4,8 @@
 from __future__ import annotations
 
 import functools
-from collections.abc import Mapping
 from dataclasses import dataclass, field
-from typing import TYPE_CHECKING, Any
+from typing import TYPE_CHECKING
 
 # pylint: disable-next=import-error
 from opentelemetry.exporter.http.transport._base import (
@@ -15,6 +14,9 @@
 )
 
 if TYPE_CHECKING:
+    from collections.abc import Mapping
+    from typing import Any
+
     import requests
     from requests import Response
 
@@ -66,6 +68,7 @@ def __init__(
         verify: bool | str = True,
         cert: str | tuple[str, str] | None = None,
         session: requests.Session | None = None,
+        **kwargs: Any,
     ) -> None:
         # pylint: disable-next=import-outside-toplevel
         import requests  # noqa: PLC0415

exporter/opentelemetry-exporter-http-transport/src/opentelemetry/exporter/http/transport/_urllib3.py

@@ -5,9 +5,8 @@
 
 import functools
 import json
-from collections.abc import Mapping
 from dataclasses import dataclass, field
-from typing import TYPE_CHECKING, Any
+from typing import TYPE_CHECKING
 
 # pylint: disable-next=import-error
 from opentelemetry.exporter.http.transport._base import (
@@ -16,6 +15,9 @@
 )
 
 if TYPE_CHECKING:
+    from collections.abc import Mapping
+    from typing import Any
+
     from urllib3 import BaseHTTPResponse
 
 
@@ -70,6 +72,7 @@ def __init__(
         *,
         verify: bool | str = True,
         cert: str | tuple[str, str] | None = None,
+        **kwargs: Any,
     ) -> None:
         # pylint: disable-next=import-outside-toplevel
         import urllib3  # noqa: PLC0415

exporter/opentelemetry-exporter-http-transport/test-requirements.in

@@ -3,4 +3,5 @@ mocket==3.14.1
 packaging==26.2
 pluggy==1.6.0
 pytest==7.4.4
+-e opentelemetry-api
 -e exporter/opentelemetry-exporter-http-transport[urllib3,requests]

exporter/opentelemetry-exporter-http-transport/test-requirements.latest.txt

@@ -2,6 +2,10 @@
 #    uv pip compile --python 3.10 --universal --resolution highest exporter/opentelemetry-exporter-http-transport/test-requirements.in -o exporter/opentelemetry-exporter-http-transport/test-requirements.latest.txt
 -e exporter/opentelemetry-exporter-http-transport
     # via -r exporter/opentelemetry-exporter-http-transport/test-requirements.in
+-e opentelemetry-api
+    # via
+    #   -r exporter/opentelemetry-exporter-http-transport/test-requirements.in
+    #   opentelemetry-exporter-http-transport
 certifi==2026.4.22
     # via requests
 charset-normalizer==3.4.7
@@ -44,6 +48,7 @@ typing-extensions==4.15.0
     # via
     #   exceptiongroup
     #   mocket
+    #   opentelemetry-api
 urllib3==2.7.0
     # via
     #   mocket

exporter/opentelemetry-exporter-http-transport/test-requirements.oldest.txt

@@ -2,6 +2,10 @@
 #    uv pip compile --python 3.10 --universal --resolution lowest-direct exporter/opentelemetry-exporter-http-transport/test-requirements.in -o exporter/opentelemetry-exporter-http-transport/test-requirements.oldest.txt
 -e exporter/opentelemetry-exporter-http-transport
     # via -r exporter/opentelemetry-exporter-http-transport/test-requirements.in
+-e opentelemetry-api
+    # via
+    #   -r exporter/opentelemetry-exporter-http-transport/test-requirements.in
+    #   opentelemetry-exporter-http-transport
 certifi==2026.4.22
     # via requests
 chardet==3.0.4
@@ -44,6 +48,7 @@ typing-extensions==4.15.0
     # via
     #   exceptiongroup
     #   mocket
+    #   opentelemetry-api
 urllib3==1.26.20
     # via
     #   mocket

exporter/opentelemetry-exporter-http-transport/tests/test_load_transport.py

@@ -0,0 +1,61 @@
+# Copyright The OpenTelemetry Authors
+# SPDX-License-Identifier: Apache-2.0
+# pylint: disable=import-error
+
+import unittest
+from unittest.mock import MagicMock, patch
+
+from opentelemetry.exporter.http.transport import _load_http_transport_factory
+from opentelemetry.exporter.http.transport._requests import (
+    RequestsHTTPTransport,
+)
+from opentelemetry.exporter.http.transport._urllib3 import (
+    Urllib3HTTPTransport,
+)
+
+_ENTRY_POINTS_TARGET = "opentelemetry.util._importlib_metadata.entry_points"
+
+
+# pylint: disable=no-self-use
+class TestLoadHTTPTransportFactory(unittest.TestCase):
+    def test_returns_requests_transport(self):
+        self.assertIs(
+            _load_http_transport_factory("requests"), RequestsHTTPTransport
+        )
+
+    def test_returns_urllib3_transport(self):
+        self.assertIs(
+            _load_http_transport_factory("urllib3"), Urllib3HTTPTransport
+        )
+
+    def test_known_transport_does_not_call_entry_points(self):
+        with patch(_ENTRY_POINTS_TARGET) as mock_ep:
+            _load_http_transport_factory("requests")
+            _load_http_transport_factory("urllib3")
+        self.assertFalse(mock_ep.called)
+
+    def test_unknown_transport_calls_entry_points(self):
+        def _custom_factory(*, verify, cert, **kwargs):
+            pass
+
+        mock_ep = MagicMock()
+        mock_ep.load.return_value = _custom_factory
+        with patch(_ENTRY_POINTS_TARGET, return_value=[mock_ep]) as mock_fn:
+            result = _load_http_transport_factory("custom")
+        self.assertEqual(
+            mock_fn.call_args.kwargs,
+            {"group": "opentelemetry_http_transport", "name": "custom"},
+        )
+        self.assertIs(result, _custom_factory)
+
+    def test_entry_point_non_callable_raises_type_error(self):
+        mock_ep = MagicMock()
+        mock_ep.load.return_value = "not_callable"
+        with patch(_ENTRY_POINTS_TARGET, return_value=[mock_ep]):
+            self.assertRaises(TypeError, _load_http_transport_factory, "bad")
+
+    def test_unknown_transport_raises_value_error(self):
+        with patch(_ENTRY_POINTS_TARGET, return_value=[]):
+            self.assertRaises(
+                ValueError, _load_http_transport_factory, "nonexistent"
+            )