Retry transient PyPI failures in metadata lookups

stub_uploader/get_version.py

@@ -15,28 +15,20 @@
 
 from typing import Any
 
-import requests
 from packaging.specifiers import Specifier, SpecifierSet
 from packaging.version import Version
-from requests.adapters import HTTPAdapter
-from urllib3.util.retry import Retry
 
 from stub_uploader.const import TYPES_PREFIX
 from stub_uploader.metadata import Metadata
+from stub_uploader.pypi import pypi_get
 
 URL_TEMPLATE = "https://pypi.org/pypi/{}/json"
-RETRIES = 5
-RETRY_ON = [429, 500, 502, 503, 504]
-TIMEOUT = 3
 
 
 def fetch_pypi_versions(distribution: str) -> list[Version]:
     assert distribution.startswith(TYPES_PREFIX)
     url = URL_TEMPLATE.format(distribution)
-    retry_strategy = Retry(total=RETRIES, status_forcelist=RETRY_ON)
-    with requests.Session() as session:
-        session.mount("https://", HTTPAdapter(max_retries=retry_strategy))
-        resp = session.get(url, timeout=TIMEOUT)
+    resp = pypi_get(url)
     if not resp.ok:
         if resp.status_code == 404:
             # Looks like this is first time this package is ever uploaded.

stub_uploader/metadata.py

@@ -27,6 +27,7 @@
     TYPES_PREFIX,
     UPLOADED_PATH,
 )
+from .pypi import DOWNLOAD_TIMEOUT, pypi_get
 
 
 class InvalidRequires(Exception):
@@ -283,7 +284,7 @@ def temp_archive_path(sdist_data: dict[str, str], req: Requirement) -> str:
     tmpdir = tempfile.mkdtemp()
     archive_path = Path(tmpdir, sdist_data["filename"])
 
-    resp = requests.get(sdist_data["url"], stream=True)
+    resp = pypi_get(sdist_data["url"], stream=True, timeout=DOWNLOAD_TIMEOUT)
     validate_pypi_response(resp, req)
     with open(archive_path, "wb") as file:
         file.write(resp.raw.read())
@@ -420,7 +421,7 @@ def get_upstream_release_metadata(
     """Fetch metadata for the latest supported, non-yanked upstream release."""
 
     project_url = f"https://pypi.org/pypi/{upstream_distribution}"
-    resp = requests.get(f"{project_url}/json")
+    resp = pypi_get(f"{project_url}/json")
     validate_pypi_response(resp, req)
     project_data = resp.json()
 
@@ -442,7 +443,7 @@ def get_upstream_release_metadata(
         )
 
     release = urllib.parse.quote(max(candidates)[1], safe="")
-    resp = requests.get(f"{project_url}/{release}/json")
+    resp = pypi_get(f"{project_url}/{release}/json")
     validate_pypi_response(resp, req)
     data: dict[str, Any] = resp.json()
     return data

stub_uploader/pypi.py

@@ -0,0 +1,43 @@
+"""HTTP access to PyPI, retried on transient failures."""
+
+from __future__ import annotations
+
+import functools
+from typing import Any
+
+import requests
+from requests.adapters import HTTPAdapter
+from urllib3.util.retry import Retry
+
+RETRIES = 5
+RETRY_ON = [429, 500, 502, 503, 504]
+# Waits 0.4, 0.8, 1.6 and 3.2 s between retries (urllib3 does not wait before the
+# first), so a brief outage does not use up every retry at once.
+BACKOFF_FACTOR = 0.2
+TIMEOUT = 3
+# For sdist downloads. A read timeout limits inactivity, not the whole transfer,
+# so a large download only fails here if the server stops sending.
+DOWNLOAD_TIMEOUT = 60
+
+
+@functools.cache
+def _session() -> requests.Session:
+    # Connection errors (including TLS EOFs) and the statuses in RETRY_ON are
+    # retried. After the last retry the final response is returned rather than
+    # raised, so callers still see the status code and report it themselves.
+    retry_strategy = Retry(
+        total=RETRIES,
+        status_forcelist=RETRY_ON,
+        backoff_factor=BACKOFF_FACTOR,
+        raise_on_status=False,
+    )
+    session = requests.Session()
+    adapter = HTTPAdapter(max_retries=retry_strategy)
+    session.mount("https://", adapter)
+    return session
+
+
+def pypi_get(url: str, **kwargs: Any) -> requests.Response:
+    """GET a URL on PyPI, retrying transient failures."""
+    kwargs.setdefault("timeout", TIMEOUT)
+    return _session().get(url, **kwargs)

tests/test_release_metadata.py

@@ -44,7 +44,7 @@ def test_supported_release_metadata(
 ) -> None:
     metadata = Metadata("example", {"version": version_spec, field: ["numpy"]}, set())
     with patch(
-        "stub_uploader.metadata.requests.get",
+        "stub_uploader.metadata.pypi_get",
         side_effect=[
             response(project_data),
             response({"info": {"requires_dist": ["numpy"]}, "urls": []}),
@@ -65,7 +65,7 @@ def test_supported_release_metadata(
 @pytest.mark.parametrize("version_spec", ["==3.*", "==1.11", "==1.12"])
 def test_no_supported_release(project_data: dict[str, Any], version_spec: str) -> None:
     with patch(
-        "stub_uploader.metadata.requests.get", return_value=response(project_data)
+        "stub_uploader.metadata.pypi_get", return_value=response(project_data)
     ) as get:
         with pytest.raises(InvalidRequires, match="No published, non-yanked release"):
             verify_external_req(
@@ -77,7 +77,7 @@ def test_no_supported_release(project_data: dict[str, Any], version_spec: str) -
 def test_dependency_must_be_in_selected_release(project_data: dict[str, Any]) -> None:
     project_data["info"]["requires_dist"] = ["numpy"]
     with patch(
-        "stub_uploader.metadata.requests.get",
+        "stub_uploader.metadata.pypi_get",
         side_effect=[
             response(project_data),
             response({"info": {"requires_dist": []}, "urls": []}),
@@ -98,7 +98,7 @@ def test_sdist_metadata_uses_selected_release(
     sdist = {"packagetype": "sdist", "filename": "example-1.10.tar.gz"}
     with (
         patch(
-            "stub_uploader.metadata.requests.get",
+            "stub_uploader.metadata.pypi_get",
             side_effect=[
                 response(project_data),
                 response({"info": {"requires_dist": []}, "urls": [sdist]}),
@@ -126,6 +126,6 @@ def test_pypi_error(project_data: dict[str, Any], release_error: bool) -> None:
     responses = [response({}, status_code=503)]
     if release_error:
         responses.insert(0, response(project_data))
-    with patch("stub_uploader.metadata.requests.get", side_effect=responses):
+    with patch("stub_uploader.metadata.pypi_get", side_effect=responses):
         with pytest.raises(InvalidRequires, match="got 503"):
             verify_external_req(Requirement("numpy"), "example", Specifier("==1.*"))