[skyyyy955]

Purpose

When KRB5CCNAME is unset, get_ticket_cache_path() calls os.getuid() to construct the Unix default cache path. On platforms without that function, including Windows, HDFS initialization can fail with AttributeError even when no Kerberos credentials are configured.

Return None when os.getuid is unavailable, after checking the explicit cache setting. This lets callers handle an unavailable cache through their existing branches. Keep explicit cache precedence, FILE: prefix handling, the Unix file-existence check, and error propagation from an available getuid. Keytab login without a discoverable cache still raises RuntimeError.

Add five regression tests and make the existing Unix-path mock work on platforms without getuid. No public API, configuration, data format or dependency changes are required. This is a platform availability fix; it does not add Kerberos cache types or certify HDFS authentication on Windows. No feature documentation changes are needed.

The existing Kerberos implementation and tests came from ChengHui Chen's #7716, merged as 81bc068. The shared helper and native backend came from chaoyang's #8031, merged as b839753. This change adds the availability guard and portability tests on top of that merged code.

Tests

The same 35 cases were run before and after the production fix against 3f5e9fcf62548a9f5bd110d4729e091b705a19b4:

Platform	Python / PyArrow	Without the production guard	With the fix
Windows	3.10.11 / 19.0.1	27 passed, 8 failed	35 passed
Linux	3.6.15 / 6.0.1	33 passed, 2 failed	35 passed
Linux	3.7.17 / 12.0.1	33 passed, 2 failed	35 passed
Linux	3.10.22 / 19.0.1	33 passed, 2 failed	35 passed

There were no skipped tests or introduced failures. The two Linux failures without the guard simulate an unavailable getuid; the other 33 cases continue to pass. All environments use the same test IDs and unchanged source inputs. From paimon-python, the selection is:

python -B -m pytest -q -p no:cacheprovider \
  pypaimon/tests/kerberos_test.py \
  pypaimon/tests/file_io_test.py::HdfsFileIOTest \
  pypaimon/tests/file_io_test.py::FileIOTest::test_write_file_with_overwrite_flag \
  pypaimon/tests/file_io_test.py::FileIOTest::test_copy_file \
  pypaimon/tests/file_io_test.py::FileIOTest::test_try_to_write_atomic \
  pypaimon/tests/file_io_test.py::FileIOTest::test_rename_returns_false_when_dst_exists \
  pypaimon/tests/file_io_test.py::FileIOTest::test_get_file_status_raises_error_when_file_not_exists \
  pypaimon/tests/file_io_test.py::FileIOTest::test_local_directory_listing_propagates_permission_errors

Changed-file flake8, the project license-header check and Python 3.6 grammar checks passed. An additional probe using the real Windows os module covered cache lookup, the public FileIO.get entry and both backend wrappers' missing-cache errors after keytab login.

HDFS clients and kinit are mocked in these tests; local file operations use real temporary files. Native backend coverage is limited to the Python wrapper. Real KDC/HDFS authentication, HDFS cluster read/write and full upstream CI have not been run for this candidate; the available HDFS endpoint was unreachable.

[JingsongLi]

+1