[2.5.x] fix whole object detection

.github/workflows/python-app.yml

@@ -7,7 +7,6 @@ on:
   push:
     branches: [ main ]
   pull_request:
-    branches: [ main ]
 
 jobs:
   check-poetry:

changelog.d/20250611_120003_jb_PL_133453_rbd_whole_object.rst

@@ -0,0 +1,3 @@
+.. A new scriv changelog fragment.
+
+- Fix whole object detection (PL-133453)

pyproject.toml

@@ -13,6 +13,18 @@ version = "literal: pyproject.toml: tool.poetry.version"
 entry_title_template = "{% if version %}{{ version }} {% endif %}({{ date.strftime('%Y-%m-%d') }})"
 categories = ""
 
+
+[tool.pytest.ini_options]
+addopts = "--timeout=30 --tb=native --cov=src --cov-report=html --cov-config=pyproject.toml src -r w"
+markers = "slow: This is a non-unit test and thus is not run by default. Use ``-m slow`` to run these, or ``-m 1`` to run all tests."
+log_level = "NOTSET"
+asyncio_mode = "auto"
+filterwarnings = [ "ignore::DeprecationWarning:telnetlib3.*:" ]
+
+[tool.coverage.run]
+branch = true
+omit = [ "*/tests/*" ]
+
 [tool.poetry]
 name = "backy"
 version = "2.5.4.dev0"
@@ -59,7 +71,7 @@ pre-commit = "^3.3.3"
 pytest = "^7.4.0"
 pytest-asyncio = "^0.21.1"
 pytest-cache = "^1.0"
-pytest-cov = "^4.1.0"
+pytest-cov = "^6.1.0"
 pytest-flake8 = "^1.1.1"
 pytest-timeout = "^2.1.0"
 scriv = "^1.3.1"

src/backy/sources/ceph/__init__.py

@@ -1,14 +1 @@
-from subprocess import PIPE, run
-
-
-def detect_whole_object_support():
-    result = run(
-        ["rbd", "help", "export-diff"], stdout=PIPE, stderr=PIPE, check=True
-    )
-    return "--whole-object" in result.stdout.decode("ascii")
-
-
-try:
-    CEPH_RBD_SUPPORTS_WHOLE_OBJECT_DIFF = detect_whole_object_support()
-except Exception:
-    CEPH_RBD_SUPPORTS_WHOLE_OBJECT_DIFF = False
+# Make this a package.

src/backy/sources/ceph/rbd.py

@@ -1,12 +1,11 @@
 import contextlib
+import functools
 import json
 import subprocess
 from typing import IO, Iterator, cast
 
 from structlog.stdlib import BoundLogger
 
-import backy.sources.ceph
-
 from ...ext_deps import RBD
 from ...utils import CHUNK_SIZE
 from .diff import RBDDiffV1
@@ -66,6 +65,10 @@ def _rbd_stream(self, cmd: list[str]) -> Iterator[IO[bytes]]:
             if rc:
                 raise subprocess.CalledProcessError(rc, proc.args)
 
+    @functools.cached_property
+    def _supports_whole_object(self):
+        return "--whole-object" in self._rbd(["help", "export-diff"])
+
     def exists(self, snapspec):
         try:
             return self._rbd(["info", snapspec], format="json")
@@ -134,7 +137,7 @@ def snap_rm(self, image):
 
     @contextlib.contextmanager
     def export_diff(self, new: str, old: str) -> Iterator[RBDDiffV1]:
-        if backy.sources.ceph.CEPH_RBD_SUPPORTS_WHOLE_OBJECT_DIFF:
+        if self._supports_whole_object:
             EXPORT_WHOLE_OBJECT = ["--whole-object"]
         else:
             EXPORT_WHOLE_OBJECT = []

src/backy/sources/ceph/tests/conftest.py

@@ -4,7 +4,6 @@
 
 import pytest
 
-import backy.sources.ceph
 from backy.sources.ceph.rbd import RBDClient
 
 
@@ -242,11 +241,8 @@ def unmap(self, device):
 
 @pytest.fixture(params=[CephJewelCLI, CephLuminousCLI, CephNautilusCLI])
 def rbdclient(request, tmpdir, monkeypatch, log):
-    monkeypatch.setattr(
-        backy.sources.ceph, "CEPH_RBD_SUPPORTS_WHOLE_OBJECT_DIFF", True
-    )
-
     client = RBDClient(log)
+    client._supports_whole_object = True
     client._ceph_cli = request.param(tmpdir)
 
     return client