Calculate linter.config.jobs in cgroupsv2 environments. Fixes pylint-…

…dev#10103

custom_dict.txt

@@ -68,6 +68,7 @@ contextlib
 contextmanager
 contravariance
 contravariant
+cgroup
 CPython
 cpython
 csv

doc/whatsnew/fragments/10103.bugfix

@@ -0,0 +1,3 @@
+Fixes a crash that occurred when pylint was run in a container on a host with cgroupsv2 and restrictions on CPU usage.
+
+Closes #10103

pylint/lint/run.py

@@ -45,26 +45,40 @@ def _query_cpu() -> int | None:
     """
     cpu_quota, avail_cpu = None, None
 
-    if Path("/sys/fs/cgroup/cpu/cpu.cfs_quota_us").is_file():
-        with open("/sys/fs/cgroup/cpu/cpu.cfs_quota_us", encoding="utf-8") as file:
-            # Not useful for AWS Batch based jobs as result is -1, but works on local linux systems
-            cpu_quota = int(file.read().rstrip())
-
-    if (
-        cpu_quota
-        and cpu_quota != -1
-        and Path("/sys/fs/cgroup/cpu/cpu.cfs_period_us").is_file()
-    ):
-        with open("/sys/fs/cgroup/cpu/cpu.cfs_period_us", encoding="utf-8") as file:
-            cpu_period = int(file.read().rstrip())
-        # Divide quota by period and you should get num of allotted CPU to the container,
-        # rounded down if fractional.
-        avail_cpu = int(cpu_quota / cpu_period)
-    elif Path("/sys/fs/cgroup/cpu/cpu.shares").is_file():
-        with open("/sys/fs/cgroup/cpu/cpu.shares", encoding="utf-8") as file:
-            cpu_shares = int(file.read().rstrip())
-        # For AWS, gives correct value * 1024.
-        avail_cpu = int(cpu_shares / 1024)
+    if Path("/sys/fs/cgroup/cpu.max").is_file():
+        # Cgroupv2 systems
+        with open("/sys/fs/cgroup/cpu.max", encoding="utf-8") as file:
+            line = file.read().rstrip()
+            fields = line.split()
+            if len(fields) == 2:
+                str_cpu_quota = fields[0]
+                cpu_period = int(fields[1])
+                # Make sure this is not in an unconstrained cgroup
+                if str_cpu_quota != "max":
+                    cpu_quota = int(str_cpu_quota)
+                    avail_cpu = int(cpu_quota / cpu_period)
+    else:
+        # Cgroupv1 systems
+        if Path("/sys/fs/cgroup/cpu/cpu.cfs_quota_us").is_file():
+            with open("/sys/fs/cgroup/cpu/cpu.cfs_quota_us", encoding="utf-8") as file:
+                # Not useful for AWS Batch based jobs as result is -1, but works on local linux systems
+                cpu_quota = int(file.read().rstrip())
+
+        if (
+            cpu_quota
+            and cpu_quota != -1
+            and Path("/sys/fs/cgroup/cpu/cpu.cfs_period_us").is_file()
+        ):
+            with open("/sys/fs/cgroup/cpu/cpu.cfs_period_us", encoding="utf-8") as file:
+                cpu_period = int(file.read().rstrip())
+            # Divide quota by period and you should get num of allotted CPU to the container,
+            # rounded down if fractional.
+            avail_cpu = int(cpu_quota / cpu_period)
+        elif Path("/sys/fs/cgroup/cpu/cpu.shares").is_file():
+            with open("/sys/fs/cgroup/cpu/cpu.shares", encoding="utf-8") as file:
+                cpu_shares = int(file.read().rstrip())
+            # For AWS, gives correct value * 1024.
+            avail_cpu = int(cpu_shares / 1024)
 
     # In K8s Pods also a fraction of a single core could be available
     # As multiprocessing is not able to run only a "fraction" of process

tests/test_pylint_runners.py

@@ -18,6 +18,7 @@
 import pytest
 
 from pylint import run_pylint, run_pyreverse, run_symilar
+from pylint.lint.run import _query_cpu
 from pylint.testutils import GenericTestReporter as Reporter
 from pylint.testutils._run import _Run as Run
 from pylint.testutils.utils import _test_cwd
@@ -90,6 +91,8 @@ def _mock_open(*args: Any, **kwargs: Any) -> BufferedReader:
     def _mock_path(*args: str, **kwargs: Any) -> pathlib.Path:
         if args[0] == "/sys/fs/cgroup/cpu/cpu.shares":
             return MagicMock(is_file=lambda: True)
+        if args[0] == "/sys/fs/cgroup/cpu.max":
+            return MagicMock(is_file=lambda: False)
         return pathlib_path(*args, **kwargs)
 
     filepath = os.path.abspath(__file__)
@@ -100,3 +103,90 @@ def _mock_path(*args: str, **kwargs: Any) -> pathlib.Path:
                 with patch("pylint.lint.run.Path", _mock_path):
                     Run(testargs, reporter=Reporter())
         assert err.value.code == 0
+
+
+@pytest.mark.parametrize(
+    "contents",
+    [
+        "1 2",
+        "max 100000",
+    ],
+)
+def test_pylint_run_jobs_equal_zero_dont_crash_with_cgroupv2(
+    tmp_path: pathlib.Path,
+    contents: str,
+) -> None:
+    """Check that the pylint runner does not crash if `pylint.lint.run._query_cpu`
+    determines only a fraction of a CPU core to be available.
+    """
+    builtin_open = open
+
+    def _mock_open(*args: Any, **kwargs: Any) -> BufferedReader:
+        if args[0] == "/sys/fs/cgroup/cpu.max":
+            return mock_open(read_data=contents)(*args, **kwargs)  # type: ignore[no-any-return]
+        return builtin_open(*args, **kwargs)  # type: ignore[no-any-return]
+
+    pathlib_path = pathlib.Path
+
+    def _mock_path(*args: str, **kwargs: Any) -> pathlib.Path:
+        if args[0] == "/sys/fs/cgroup/cpu/cpu.shares":
+            return MagicMock(is_file=lambda: False)
+        if args[0] == "/sys/fs/cgroup/cpu/cfs_quota_us":
+            return MagicMock(is_file=lambda: False)
+        if args[0] == "/sys/fs/cgroup/cpu.max":
+            return MagicMock(is_file=lambda: True)
+        return pathlib_path(*args, **kwargs)
+
+    filepath = os.path.abspath(__file__)
+    testargs = [filepath, "--jobs=0"]
+    with _test_cwd(tmp_path):
+        with pytest.raises(SystemExit) as err:
+            with patch("builtins.open", _mock_open):
+                with patch("pylint.lint.run.Path", _mock_path):
+                    Run(testargs, reporter=Reporter())
+        assert err.value.code == 0
+
+
+@pytest.mark.parametrize(
+    "contents,expected",
+    [
+        ("50000 100000", 1),
+        ("100000 100000", 1),
+        ("200000 100000", 2),
+        ("299999 100000", 2),
+        ("300000 100000", 3),
+        # Unconstrained cgroup
+        ("max 100000", None),
+    ],
+)
+def test_query_cpu_cgroupv2(
+    tmp_path: pathlib.Path,
+    contents: str,
+    expected: int,
+) -> None:
+    """Check that `pylint.lint.run._query_cpu` generates realistic values in cgroupsv2
+    systems.
+    """
+    builtin_open = open
+
+    def _mock_open(*args: Any, **kwargs: Any) -> BufferedReader:
+        if args[0] == "/sys/fs/cgroup/cpu.max":
+            return mock_open(read_data=contents)(*args, **kwargs)  # type: ignore[no-any-return]
+        return builtin_open(*args, **kwargs)  # type: ignore[no-any-return]
+
+    pathlib_path = pathlib.Path
+
+    def _mock_path(*args: str, **kwargs: Any) -> pathlib.Path:
+        if args[0] == "/sys/fs/cgroup/cpu/cpu.shares":
+            return MagicMock(is_file=lambda: False)
+        if args[0] == "/sys/fs/cgroup/cpu/cfs_quota_us":
+            return MagicMock(is_file=lambda: False)
+        if args[0] == "/sys/fs/cgroup/cpu.max":
+            return MagicMock(is_file=lambda: True)
+        return pathlib_path(*args, **kwargs)
+
+    with _test_cwd(tmp_path):
+        with patch("builtins.open", _mock_open):
+            with patch("pylint.lint.run.Path", _mock_path):
+                cpus = _query_cpu()
+                assert cpus == expected