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community.general/lib/ansible/modules/files/file.py
Mark Mielke b4a1542670 Reduce the system calls performed by the "file" module 
when using "state: link", and particularly when using
"force: yes".

Symbolic link resolution can be expensive. In our case,
the symbolic links are legacy links to automounts, and
the "file" task was causing all of the legacy links to
be traversed and mounted on every host every time the
task executed, even when the links were correct and there
was nothing to do.

This change avoids the system calls that perform the
symbolic link resolution by taking advantage of the short
circuit behaviur of the boolean "and" operator. The code
behaviour is unchanged except that it no longer performs
unnecessary system calls.

As it turns out, this change is not sufficient to fully
solve the symbolic link resolution problem, as the "file"
module still performs a stat() at the end of execution to
provide the caller with information about the file.
However, this change is very simple, it will eliminate
unnecessary system calls in a number of use cases, and it
gets the "file" module closer to the desired end result.
2017-01-24 12:31:25 -08:00

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#!/usr/bin/python
# -*- coding: utf-8 -*-
# (c) 2012, Michael DeHaan <michael.dehaan@gmail.com>
#
# This file is part of Ansible
#
# Ansible is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Ansible is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Ansible. If not, see <http://www.gnu.org/licenses/>.
ANSIBLE_METADATA = {'status': ['stableinterface'],
'supported_by': 'core',
'version': '1.0'}
DOCUMENTATION = '''
---
module: file
version_added: "historical"
short_description: Sets attributes of files
extends_documentation_fragment: files
description:
- Sets attributes of files, symlinks, and directories, or removes
files/symlinks/directories. Many other modules support the same options as
the M(file) module - including M(copy), M(template), and M(assemble).
notes:
- See also M(copy), M(template), M(assemble)
requirements: [ ]
author:
- "Ansible Core Team"
- "Michael DeHaan"
options:
path:
description:
- 'path to the file being managed. Aliases: I(dest), I(name)'
required: true
default: []
aliases: ['dest', 'name']
state:
description:
- If C(directory), all immediate subdirectories will be created if they
do not exist, since 1.7 they will be created with the supplied permissions.
If C(file), the file will NOT be created if it does not exist, see the M(copy)
or M(template) module if you want that behavior. If C(link), the symbolic
link will be created or changed. Use C(hard) for hardlinks. If C(absent),
directories will be recursively deleted, and files or symlinks will be unlinked.
Note that M(file) will not fail if the C(path) does not exist as the state did not change.
If C(touch) (new in 1.4), an empty file will be created if the C(path) does not
exist, while an existing file or directory will receive updated file access and
modification times (similar to the way `touch` works from the command line).
required: false
default: file
choices: [ file, link, directory, hard, touch, absent ]
src:
required: false
default: null
description:
- path of the file to link to (applies only to C(state=link)). Will accept absolute,
relative and nonexisting paths. Relative paths are not expanded.
recurse:
required: false
default: "no"
choices: [ "yes", "no" ]
version_added: "1.1"
description:
- recursively set the specified file attributes (applies only to state=directory)
force:
required: false
default: "no"
choices: [ "yes", "no" ]
description:
- 'force the creation of the symlinks in two cases: the source file does
not exist (but will appear later); the destination exists and is a file (so, we need to unlink the
"path" file and create symlink to the "src" file in place of it).'
follow:
required: false
default: "no"
choices: [ "yes", "no" ]
version_added: "1.8"
description:
- 'This flag indicates that filesystem links, if they exist, should be followed.'
'''
EXAMPLES = '''
# change file ownership, group and mode. When specifying mode using octal numbers, first digit should always be 0.
- file:
path: /etc/foo.conf
owner: foo
group: foo
mode: 0644
- file:
src: /file/to/link/to
dest: /path/to/symlink
owner: foo
group: foo
state: link
- file:
src: '/tmp/{{ item.src }}'
dest: '{{ item.dest }}'
state: link
with_items:
- { src: 'x', dest: 'y' }
- { src: 'z', dest: 'k' }
# touch a file, using symbolic modes to set the permissions (equivalent to 0644)
- file:
path: /etc/foo.conf
state: touch
mode: "u=rw,g=r,o=r"
# touch the same file, but add/remove some permissions
- file:
path: /etc/foo.conf
state: touch
mode: "u+rw,g-wx,o-rwx"
# create a directory if it doesn't exist
- file:
path: /etc/some_directory
state: directory
mode: 0755
'''
import errno
import os
import shutil
import time
# import module snippets
from ansible.module_utils.basic import AnsibleModule
from ansible.module_utils.pycompat24 import get_exception
from ansible.module_utils.six import b
from ansible.module_utils._text import to_bytes, to_native
def get_state(b_path):
''' Find out current state '''
if os.path.lexists(b_path):
if os.path.islink(b_path):
return 'link'
elif os.path.isdir(b_path):
return 'directory'
elif os.stat(b_path).st_nlink > 1:
return 'hard'
else:
# could be many other things, but defaulting to file
return 'file'
return 'absent'
def recursive_set_attributes(module, b_path, follow, file_args):
changed = False
for b_root, b_dirs, b_files in os.walk(b_path):
for b_fsobj in b_dirs + b_files:
b_fsname = os.path.join(b_root, b_fsobj)
if not os.path.islink(b_fsname):
tmp_file_args = file_args.copy()
tmp_file_args['path'] = to_native(b_fsname, errors='surrogate_or_strict')
changed |= module.set_fs_attributes_if_different(tmp_file_args, changed)
else:
tmp_file_args = file_args.copy()
tmp_file_args['path'] = to_native(b_fsname, errors='surrogate_or_strict')
changed |= module.set_fs_attributes_if_different(tmp_file_args, changed)
if follow:
b_fsname = os.path.join(b_root, os.readlink(b_fsname))
if os.path.isdir(b_fsname):
changed |= recursive_set_attributes(module, b_fsname, follow, file_args)
tmp_file_args = file_args.copy()
tmp_file_args['path'] = to_native(b_fsname, errors='surrogate_or_strict')
changed |= module.set_fs_attributes_if_different(tmp_file_args, changed)
return changed
def main():
module = AnsibleModule(
argument_spec=dict(
state=dict(choices=['file', 'directory', 'link', 'hard', 'touch', 'absent'], default=None),
path=dict(aliases=['dest', 'name'], required=True, type='path'),
original_basename=dict(required=False), # Internal use only, for recursive ops
recurse=dict(default=False, type='bool'),
force=dict(required=False, default=False, type='bool'),
diff_peek=dict(default=None), # Internal use only, for internal checks in the action plugins
validate=dict(required=False, default=None), # Internal use only, for template and copy
src=dict(required=False, default=None, type='path'),
),
add_file_common_args=True,
supports_check_mode=True
)
params = module.params
state = params['state']
force = params['force']
diff_peek = params['diff_peek']
src = params['src']
b_src = to_bytes(src, errors='surrogate_or_strict')
follow = params['follow']
# modify source as we later reload and pass, specially relevant when used by other modules.
path = params['path']
b_path = to_bytes(path, errors='surrogate_or_strict')
# short-circuit for diff_peek
if diff_peek is not None:
appears_binary = False
try:
f = open(b_path, 'rb')
head = f.read(8192)
f.close()
if b("\x00") in head:
appears_binary = True
except:
pass
module.exit_json(path=path, changed=False, appears_binary=appears_binary)
prev_state = get_state(b_path)
# state should default to file, but since that creates many conflicts,
# default to 'current' when it exists.
if state is None:
if prev_state != 'absent':
state = prev_state
else:
state = 'file'
# source is both the source of a symlink or an informational passing of the src for a template module
# or copy module, even if this module never uses it, it is needed to key off some things
if src is None:
if state in ('link', 'hard'):
if follow and state == 'link':
# use the current target of the link as the source
src = to_native(os.path.realpath(b_path), errors='strict')
b_src = to_bytes(os.path.realpath(b_path), errors='strict')
else:
module.fail_json(msg='src and dest are required for creating links')
# original_basename is used by other modules that depend on file.
if state not in ("link", "absent") and os.path.isdir(b_path):
basename = None
if params['original_basename']:
basename = params['original_basename']
elif src is not None:
basename = os.path.basename(src)
if basename:
params['path'] = path = os.path.join(path, basename)
b_path = to_bytes(path, errors='surrogate_or_strict')
# make sure the target path is a directory when we're doing a recursive operation
recurse = params['recurse']
if recurse and state != 'directory':
module.fail_json(path=path, msg="recurse option requires state to be 'directory'")
file_args = module.load_file_common_arguments(params)
changed = False
diff = {'before': {'path': path},
'after': {'path': path},
}
state_change = False
if prev_state != state:
diff['before']['state'] = prev_state
diff['after']['state'] = state
state_change = True
if state == 'absent':
if state_change:
if not module.check_mode:
if prev_state == 'directory':
try:
shutil.rmtree(b_path, ignore_errors=False)
except Exception:
e = get_exception()
module.fail_json(msg="rmtree failed: %s" % str(e))
else:
try:
os.unlink(b_path)
except Exception:
e = get_exception()
module.fail_json(path=path, msg="unlinking failed: %s " % str(e))
module.exit_json(path=path, changed=True, diff=diff)
else:
module.exit_json(path=path, changed=False)
elif state == 'file':
if state_change:
if follow and prev_state == 'link':
# follow symlink and operate on original
b_path = os.path.realpath(b_path)
path = to_native(b_path, errors='strict')
prev_state = get_state(b_path)
file_args['path'] = path
if prev_state not in ('file', 'hard'):
# file is not absent and any other state is a conflict
module.fail_json(path=path, msg='file (%s) is %s, cannot continue' % (path, prev_state))
changed = module.set_fs_attributes_if_different(file_args, changed, diff)
module.exit_json(path=path, changed=changed, diff=diff)
elif state == 'directory':
if follow and prev_state == 'link':
b_path = os.path.realpath(b_path)
path = to_native(b_path, errors='strict')
prev_state = get_state(b_path)
if prev_state == 'absent':
if module.check_mode:
module.exit_json(changed=True, diff=diff)
changed = True
curpath = ''
try:
# Split the path so we can apply filesystem attributes recursively
# from the root (/) directory for absolute paths or the base path
# of a relative path. We can then walk the appropriate directory
# path to apply attributes.
for dirname in path.strip('/').split('/'):
curpath = '/'.join([curpath, dirname])
# Remove leading slash if we're creating a relative path
if not os.path.isabs(path):
curpath = curpath.lstrip('/')
b_curpath = to_bytes(curpath, errors='surrogate_or_strict')
if not os.path.exists(b_curpath):
try:
os.mkdir(b_curpath)
except OSError:
ex = get_exception()
# Possibly something else created the dir since the os.path.exists
# check above. As long as it's a dir, we don't need to error out.
if not (ex.errno == errno.EEXIST and os.path.isdir(b_curpath)):
raise
tmp_file_args = file_args.copy()
tmp_file_args['path'] = curpath
changed = module.set_fs_attributes_if_different(tmp_file_args, changed, diff)
except Exception:
e = get_exception()
module.fail_json(path=path, msg='There was an issue creating %s as requested: %s' % (curpath, str(e)))
# We already know prev_state is not 'absent', therefore it exists in some form.
elif prev_state != 'directory':
module.fail_json(path=path, msg='%s already exists as a %s' % (path, prev_state))
changed = module.set_fs_attributes_if_different(file_args, changed, diff)
if recurse:
changed |= recursive_set_attributes(module, to_bytes(file_args['path'], errors='surrogate_or_strict'), follow, file_args)
module.exit_json(path=path, changed=changed, diff=diff)
elif state in ('link', 'hard'):
if not os.path.islink(b_path) and os.path.isdir(b_path):
relpath = path
else:
b_relpath = os.path.dirname(b_path)
relpath = to_native(b_relpath, errors='strict')
absrc = os.path.join(relpath, src)
b_absrc = to_bytes(absrc, errors='surrogate_or_strict')
if not force and not os.path.exists(b_absrc):
module.fail_json(path=path, src=src, msg='src file does not exist, use "force=yes" if you really want to create the link: %s' % absrc)
if state == 'hard':
if not os.path.isabs(b_src):
module.fail_json(msg="absolute paths are required")
elif prev_state == 'directory':
if not force:
module.fail_json(path=path, msg='refusing to convert between %s and %s for %s' % (prev_state, state, path))
elif len(os.listdir(b_path)) > 0:
# refuse to replace a directory that has files in it
module.fail_json(path=path, msg='the directory %s is not empty, refusing to convert it' % path)
elif prev_state in ('file', 'hard') and not force:
module.fail_json(path=path, msg='refusing to convert between %s and %s for %s' % (prev_state, state, path))
if prev_state == 'absent':
changed = True
elif prev_state == 'link':
b_old_src = os.readlink(b_path)
if b_old_src != b_src:
changed = True
elif prev_state == 'hard':
if not (state == 'hard' and os.stat(b_path).st_ino == os.stat(b_src).st_ino):
changed = True
if not force:
module.fail_json(dest=path, src=src, msg='Cannot link, different hard link exists at destination')
elif prev_state in ('file', 'directory'):
changed = True
if not force:
module.fail_json(dest=path, src=src, msg='Cannot link, %s exists at destination' % prev_state)
else:
module.fail_json(dest=path, src=src, msg='unexpected position reached')
if changed and not module.check_mode:
if prev_state != 'absent':
# try to replace atomically
b_tmppath = to_bytes(os.path.sep).join(
[os.path.dirname(b_path), to_bytes(".%s.%s.tmp" % (os.getpid(), time.time()))]
)
try:
if prev_state == 'directory' and (state == 'hard' or state == 'link'):
os.rmdir(b_path)
if state == 'hard':
os.link(b_src, b_tmppath)
else:
os.symlink(b_src, b_tmppath)
os.rename(b_tmppath, b_path)
except OSError:
e = get_exception()
if os.path.exists(b_tmppath):
os.unlink(b_tmppath)
module.fail_json(path=path, msg='Error while replacing: %s' % to_native(e, nonstring='simplerepr'))
else:
try:
if state == 'hard':
os.link(b_src, b_path)
else:
os.symlink(b_src, b_path)
except OSError:
e = get_exception()
module.fail_json(path=path, msg='Error while linking: %s' % to_native(e, nonstring='simplerepr'))
if module.check_mode and not os.path.exists(b_path):
module.exit_json(dest=path, src=src, changed=changed, diff=diff)
changed = module.set_fs_attributes_if_different(file_args, changed, diff)
module.exit_json(dest=path, src=src, changed=changed, diff=diff)
elif state == 'touch':
if not module.check_mode:
if prev_state == 'absent':
try:
open(b_path, 'wb').close()
except OSError:
e = get_exception()
module.fail_json(path=path, msg='Error, could not touch target: %s' % to_native(e, nonstring='simplerepr'))
elif prev_state in ('file', 'directory', 'hard'):
try:
os.utime(b_path, None)
except OSError:
e = get_exception()
module.fail_json(path=path, msg='Error while touching existing target: %s' % to_native(e, nonstring='simplerepr'))
else:
module.fail_json(msg='Cannot touch other than files, directories, and hardlinks (%s is %s)' % (path, prev_state))
try:
module.set_fs_attributes_if_different(file_args, True, diff)
except SystemExit:
e = get_exception()
if e.code:
# We take this to mean that fail_json() was called from
# somewhere in basic.py
if prev_state == 'absent':
# If we just created the file we can safely remove it
os.remove(b_path)
raise e
module.exit_json(dest=path, changed=True, diff=diff)
module.fail_json(path=path, msg='unexpected position reached')
if __name__ == '__main__':
main()
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