def test_atomic_writer_success(tmp_path):
dst = tmp_path / "dst"
with atomic_writer(dst) as tmp:
tmp.write_text("dst")
assert dst.read_text() == "dst"
assert not tmp.exists()
def test_atomic_writer_failure(tmp_path):
dst = tmp_path / "dst"
with pytest.raises(Exception):
with atomic_writer(dst) as tmp:
tmp.write_text("dst")
raise Exception("test")
assert not dst.exists()
assert not tmp.exists()
def copy_file(source, dest, follow_symlinks=True):
"""Efficient atomic copy.
shutil.copy uses sendfile on linux, so should be fast.
"""
# ensure path
dest = Path(dest)
dest.parent.mkdir(parents=True, exist_ok=True)
with atomic_writer(dest) as tmp:
shutil.copy(source, tmp, follow_symlinks=follow_symlinks)
def test_atomic_writer_overwrite_symlink(tmp_path):
target = tmp_path / "target"
target.write_text("target")
dst = tmp_path / "link"
dst.symlink_to(target)
with atomic_writer(dst) as tmp:
tmp.write_text("dst")
assert dst.read_text() == "dst"
assert not dst.is_symlink()
assert target.read_text() == "target"
assert not tmp.exists()
def copy_from_volume(volume_name, source, dest, timeout=None):
"""
Copy the contents of `source` from the root of the named volume to `dest`
on local disk
As this command can potentially take a long time with large files it does
not, by default, have any timeout.
"""
with atomic_writer(dest) as tmp:
docker(
[
"cp",
"--follow-link",
f"{manager_name(volume_name)}:{VOLUME_MOUNT_POINT}/{source}",
tmp,
],
check=True,
capture_output=True,
timeout=timeout,
)