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# Copyright 2010 Canonical Ltd. This software is licensed under the
# GNU Affero General Public License version 3 (see the file LICENSE).
"""Helpers for creating and removing a read-only.txt in the root of our tree.
"""
__metaclass__ = type
__all__ = [
'touch_read_only_file',
'read_only_mode',
'remove_read_only_file',
]
from contextlib import contextmanager
import os
from lazr.restful.utils import get_current_browser_request
from lp.services.database.readonly import (
is_read_only,
read_only_file_exists,
read_only_file_path,
READ_ONLY_MODE_ANNOTATIONS_KEY,
)
def touch_read_only_file():
"""Create an empty file named read-only.txt under the root of the tree.
This function must not be called if a file with that name already exists.
"""
assert not read_only_file_exists(), (
"This function must not be called when a read-only.txt file "
"already exists.")
f = open(read_only_file_path, 'w')
f.close()
# Assert that the switch succeeded and make sure the mode change is
# logged.
assert is_read_only(), "Switching to read-only failed."
def remove_read_only_file(assert_mode_switch=True):
"""Remove the file named read-only.txt from the root of the tree.
May also assert that the mode switch actually happened (i.e. not
is_read_only()). This assertion has to be conditional because some tests
will use this during the processing of a request, when a mode change can't
happen (i.e. is_read_only() will still return True during that request's
processing, even though the read-only.txt file has been removed).
"""
os.remove(read_only_file_path)
if assert_mode_switch:
# Assert that the switch succeeded and make sure the mode change is
# logged.
assert not is_read_only(), "Switching to read-write failed."
@contextmanager
def read_only_mode(flag=True):
request = get_current_browser_request()
current = request.annotations[READ_ONLY_MODE_ANNOTATIONS_KEY]
request.annotations[READ_ONLY_MODE_ANNOTATIONS_KEY] = flag
try:
assert is_read_only() == flag, 'Failed to set read-only mode'
yield
finally:
request.annotations[READ_ONLY_MODE_ANNOTATIONS_KEY] = current
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