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# Copyright 2012-2014 Canonical Ltd. This software is licensed under the
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# GNU Affero General Public License version 3 (see the file LICENSE).
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"""Utilities for the provisioning server."""
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from __future__ import (
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"parse_key_value_file",
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"write_custom_config_section",
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from argparse import ArgumentParser
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from contextlib import contextmanager
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from functools import wraps
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from os.path import isdir
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from pipes import quote
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from shutil import rmtree
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from subprocess import (
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from crochet import run_in_reactor
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from lockfile import FileLock
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from lxml import etree
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from twisted.internet.defer import maybeDeferred
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from twisted.python.threadable import isInIOThread
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# A table suitable for use with str.translate() to replace each
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# non-printable and non-ASCII character in a byte string with a question
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# mark, mimicking the "replace" strategy when encoding and decoding.
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non_printable_replace_table = b"".join(
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chr(i) if chr(i) in string.printable else b"?"
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for i in xrange(0xff + 0x01))
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class ExternalProcessError(CalledProcessError):
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"""Raised when there's a problem calling an external command.
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Unlike `CalledProcessError`:
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- `__str__()` returns a string containing the output of the failed
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external process, if available. All non-printable and non-ASCII
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characters are filtered out, replaced by question marks.
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- `__unicode__()` is defined, and tries to return something
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analagous to `__str__()` but keeping in valid unicode characters
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from the error message.
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def _to_unicode(string):
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if isinstance(string, bytes):
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return string.decode("ascii", "replace")
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return unicode(string)
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def _to_ascii(string, table=non_printable_replace_table):
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if isinstance(string, unicode):
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return string.encode("ascii", "replace")
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return bytes(string).translate(table)
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def __unicode__(self):
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cmd = u" ".join(quote(self._to_unicode(part)) for part in self.cmd)
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output = self._to_unicode(self.output)
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return u"Command `%s` returned non-zero exit status %d:\n%s" % (
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cmd, self.returncode, output)
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cmd = b" ".join(quote(self._to_ascii(part)) for part in self.cmd)
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output = self._to_ascii(self.output)
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return b"Command `%s` returned non-zero exit status %d:\n%s" % (
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cmd, self.returncode, output)
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def call_and_check(command, *args, **kwargs):
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"""A wrapper around subprocess.check_call().
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When an error occurs, raise an ExternalProcessError.
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return subprocess.check_call(command, *args, **kwargs)
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except subprocess.CalledProcessError as error:
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error.__class__ = ExternalProcessError
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def call_capture_and_check(command, *args, **kwargs):
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"""A wrapper around subprocess.check_output().
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When an error occurs, raise an ExternalProcessError.
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return subprocess.check_output(command, *args, **kwargs)
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except subprocess.CalledProcessError as error:
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error.__class__ = ExternalProcessError
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def locate_config(*path):
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"""Return the location of a given config file or directory.
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Defaults to `/etc/maas` (followed by any further path elements you
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specify), but can be overridden using the `MAAS_CONFIG_DIR` environment
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variable. (When running from a branch, this variable will point to the
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`etc/maas` inside the branch.)
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The result is absolute and normalized.
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# Check for MAAS_CONFIG_DIR. Count empty string as "not set."
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env_setting = os.getenv('MAAS_CONFIG_DIR', '')
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if env_setting == '':
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# Running from installed package. Config is in /etc/maas.
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config_dir = '/etc/maas'
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# Running from branch or other customized setup. Config is at
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# $MAAS_CONFIG_DIR/etc/maas.
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config_dir = env_setting
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return os.path.abspath(os.path.join(config_dir, *path))
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def find_settings(whence):
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"""Return settings from `whence`, which is assumed to be a module."""
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# XXX 2012-10-11 JeroenVermeulen, bug=1065456: Put this in a shared
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# location. It's currently duplicated from elsewhere.
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for name, value in vars(whence).items()
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if not name.startswith("_")
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def import_settings(whence):
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"""Import settings from `whence` into the caller's global scope."""
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# XXX 2012-10-11 JeroenVermeulen, bug=1065456: Put this in a shared
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# location. It's currently duplicated from elsewhere.
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source = find_settings(whence)
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target = sys._getframe(1).f_globals
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target.update(source)
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"""Decorates a function to ensure that it always returns a `Deferred`.
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This also serves a secondary documentation purpose; functions decorated
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with this are readily identifiable as asynchronous.
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def wrapper(*args, **kwargs):
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return maybeDeferred(func, *args, **kwargs)
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def asynchronous(func):
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"""Decorates a function to ensure that it always runs in the reactor.
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If the wrapper is called from the reactor thread, it will call
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straight through to the wrapped function. It will not be wrapped by
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`maybeDeferred` for example.
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If the wrapper is called from another thread, it will return a
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:class:`crochet.EventualResult`, as if it had been decorated with
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`crochet.run_in_reactor`.
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This also serves a secondary documentation purpose; functions decorated
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with this are readily identifiable as asynchronous.
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func_in_reactor = run_in_reactor(func)
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def wrapper(*args, **kwargs):
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return func(*args, **kwargs)
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return func_in_reactor(*args, **kwargs)
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def synchronous(func):
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"""Decorator to ensure that `func` never runs in the reactor thread.
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If the wrapped function is called from the reactor thread, this will
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raise a :class:`AssertionError`, implying that this is a programming
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error. Calls from outside the reactor will proceed unaffected.
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There is an asymettry with the `asynchronous` decorator. The reason
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is that it is essential to be aware when `deferToThread()` is being
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used, so that in-reactor code knows to synchronise with it, to add a
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callback to the :class:`Deferred` that it returns, for example. The
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expectation with `asynchronous` is that the return value is always
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important, and will be appropriate to the environment in which it is
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This also serves a secondary documentation purpose; functions decorated
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with this are readily identifiable as synchronous, or blocking.
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:raises AssertionError: When called inside the reactor thread.
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def wrapper(*args, **kwargs):
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raise AssertionError(
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"Function %s(...) must not be called in the "
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"reactor thread." % func.__name__)
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return func(*args, **kwargs)
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def filter_dict(dictionary, desired_keys):
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"""Return a version of `dictionary` restricted to `desired_keys`.
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This is like a set union, except the values from `dictionary` come along.
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(Actually `desired_keys` can be a `dict`, but its values will be ignored).
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for key, value in dictionary.items()
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if key in desired_keys
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def _write_temp_file(content, filename):
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"""Write the given `content` in a temporary file next to `filename`."""
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# Write the file to a temporary place (next to the target destination,
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# to ensure that it is on the same filesystem).
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directory = os.path.dirname(filename)
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prefix = ".%s." % os.path.basename(filename)
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temp_fd, temp_file = tempfile.mkstemp(
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dir=directory, suffix=suffix, prefix=prefix)
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except OSError, error:
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if error.filename is None:
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error.filename = os.path.join(
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directory, prefix + "XXXXXX" + suffix)
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with os.fdopen(temp_fd, "wb") as f:
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# Finish writing this file to the filesystem, and then, tell the
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# filesystem to push it down onto persistent storage. This
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# prevents a nasty hazard in aggressively optimized filesystems
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# where you replace an old but consistent file with a new one that
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# is still in cache, and lose power before the new file can be made
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# This was a particular problem with ext4 at one point; it may
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def atomic_write(content, filename, overwrite=True, mode=0600):
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"""Write `content` into the file `filename` in an atomic fashion.
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This requires write permissions to the directory that `filename` is in.
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It creates a temporary file in the same directory (so that it will be
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on the same filesystem as the destination) and then renames it to
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replace the original, if any. Such a rename is atomic in POSIX.
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:param overwrite: Overwrite `filename` if it already exists? Default
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:param mode: Access permissions for the file, if written.
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temp_file = _write_temp_file(content, filename)
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os.chmod(temp_file, mode)
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os.rename(temp_file, filename)
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lock = FileLock(filename)
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if not os.path.isfile(filename):
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os.rename(temp_file, filename)
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if os.path.isfile(temp_file):
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def incremental_write(content, filename, mode=0600):
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"""Write the given `content` into the file `filename` and
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increment the modification time by 1 sec.
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:param mode: Access permissions for the file.
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old_mtime = get_mtime(filename)
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atomic_write(content, filename, mode=mode)
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new_mtime = pick_new_mtime(old_mtime)
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os.utime(filename, (new_mtime, new_mtime))
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def get_mtime(filename):
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"""Return a file's modification time, or None if it does not exist."""
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return os.stat(filename).st_mtime
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if e.errno == errno.ENOENT:
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# File does not exist. Be helpful, return None.
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# Other failure. The caller will want to know.
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def pick_new_mtime(old_mtime=None, starting_age=1000):
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"""Choose a new modification time for a file that needs it updated.
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This function is used to manage the modification time of files
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for which we need to see an increment in the modification time
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each time the file is modified. This is the case for DNS zone
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files which only get properly reloaded if BIND sees that the
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modification time is > to the time it has in its database.
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Modification time can have a resolution as low as one second in
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some relevant environments (we have observed this with ext3).
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To produce mtime changes regardless, we set a file's modification
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time in the past when it is first written, and
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increment it by 1 second on each subsequent write.
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However we also want to be careful not to set the modification time
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in the future, mostly because BIND does not deal with that very
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:param old_mtime: File's previous modification time, as a number
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with a unity of one second, or None if it did not previously
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:param starting_age: If the file did not exist previously, set its
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modification time this many seconds in the past.
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if old_mtime is None:
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# File is new. Set modification time in the past to have room for
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# sub-second modifications.
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return now - starting_age
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elif old_mtime + 1 <= now:
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# There is room to increment the file's mtime by one second
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# without ending up in the future.
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# We can't increase the file's modification time. Give up and
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# return the previous modification time.
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def split_lines(input, separator):
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"""Split each item from `input` into a key/value pair."""
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return (line.split(separator, 1) for line in input if line.strip() != '')
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def strip_pairs(input):
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"""Strip whitespace of each key/value pair in input."""
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return ((key.strip(), value.strip()) for (key, value) in input)
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def parse_key_value_file(file_name, separator=":"):
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"""Parse a text file into a dict of key/value pairs.
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Use this for simple key:value or key=value files. There are no
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sections, as required for python's ConfigParse. Whitespace and empty
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:param file_name: Name of file to parse.
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:param separator: The text that separates each key from its value.
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with open(file_name, 'rb') as input:
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return dict(strip_pairs(split_lines(input, separator)))
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# Header and footer comments for MAAS custom config sections, as managed
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# by write_custom_config_section.
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maas_custom_config_markers = (
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"## Begin MAAS settings. Do not edit; MAAS will overwrite this section.",
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"## End MAAS settings.",
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def find_list_item(item, in_list, starting_at=0):
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"""Return index of `item` in `in_list`, or None if not found."""
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return in_list.index(item, starting_at)
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def write_custom_config_section(original_text, custom_section):
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"""Insert or replace a custom section in a configuration file's text.
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This allows you to rewrite configuration files that are not owned by
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MAAS, but where MAAS will have one section for its own settings. It
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doesn't read or write any files; this is a pure text operation.
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Appends `custom_section` to the end of `original_text` if there was no
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custom MAAS section yet. Otherwise, replaces the existing custom MAAS
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section with `custom_section`. Returns the new text.
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Assumes that the configuration file's format accepts lines starting with
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hash marks (#) as comments. The custom section will be bracketed by
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special marker comments that make it clear that MAAS wrote the section
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and it should not be edited by hand.
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:param original_text: The config file's current text.
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:type original_text: unicode
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:param custom_section: Custom config section to insert.
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:type custom_section: unicode
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:return: New config file text.
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header, footer = maas_custom_config_markers
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lines = original_text.splitlines()
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header_index = find_list_item(header, lines)
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if header_index is not None:
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footer_index = find_list_item(footer, lines, header_index)
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if footer_index is None:
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# There's a header but no footer. Pretend we didn't see the
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# header; just append a new custom section at the end. Any
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# subsequent rewrite will replace the part starting at the
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# header and ending at the header we will add here. At that
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# point there will be no trace of the strange situation
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if header_index is None:
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# There was no MAAS custom section in this file. Append it at
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# There is a MAAS custom section in the file. Replace it.
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lines[:(header_index + 1)] +
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lines[footer_index:])
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return '\n'.join(lines) + '\n'
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def sudo_write_file(filename, contents, encoding='utf-8', mode=0644):
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"""Write (or overwrite) file as root. USE WITH EXTREME CARE.
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Runs an atomic update using non-interactive `sudo`. This will fail if
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it needs to prompt for a password.
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raw_contents = contents.encode(encoding)
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'sudo', '-n', 'maas-provision', 'atomic-write',
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'--filename', filename,
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proc = Popen(command, stdin=PIPE)
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stdout, stderr = proc.communicate(raw_contents)
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if proc.returncode != 0:
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raise ExternalProcessError(proc.returncode, command, stderr)
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"""An object that is safe to render as-is."""
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__slots__ = ("value",)
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def __init__(self, value):
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self.__class__.__name__, self.value)
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class ShellTemplate(tempita.Template):
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"""A Tempita template specialised for writing shell scripts.
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By default, substitutions will be escaped using `pipes.quote`, unless
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they're marked as safe. This can be done using Tempita's filter syntax::
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or as a plain Python expression::
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default_namespace = dict(
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tempita.Template.default_namespace,
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def _repr(self, value, pos):
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"""Shell-quote the value by default."""
535
rep = super(ShellTemplate, self)._repr
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if isinstance(value, Safe):
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return rep(value.value, pos)
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return quote(rep(value, pos))
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"""A command-line script that follows a command+verb pattern."""
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def __init__(self, description):
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super(ActionScript, self).__init__()
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# See http://docs.python.org/release/2.7/library/argparse.html.
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self.parser = ArgumentParser(description=description)
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self.subparsers = self.parser.add_subparsers(title="actions")
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# Ensure stdout and stderr are line-bufferred.
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sys.stdout = fdopen(sys.stdout.fileno(), "ab", 1)
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sys.stderr = fdopen(sys.stderr.fileno(), "ab", 1)
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# Run the SIGINT handler on SIGTERM; `svc -d` sends SIGTERM.
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signal.signal(signal.SIGTERM, signal.default_int_handler)
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def register(self, name, handler, *args, **kwargs):
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"""Register an action for the given name.
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:param name: The name of the action.
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:param handler: An object, a module for example, that has `run` and
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`add_arguments` callables. The docstring of the `run` callable is
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used as the help text for the newly registered action.
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:param args: Additional positional arguments for the subparser_.
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:param kwargs: Additional named arguments for the subparser_.
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http://docs.python.org/
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release/2.7/library/argparse.html#sub-commands
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parser = self.subparsers.add_parser(
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name, *args, help=handler.run.__doc__, **kwargs)
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parser.set_defaults(handler=handler)
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handler.add_arguments(parser)
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def execute(self, argv=None):
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"""Execute this action.
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This is intended for in-process invocation of an action, though it may
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still raise L{SystemExit}. The L{__call__} method is intended for when
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this object is executed as a script proper.
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args = self.parser.parse_args(argv)
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args.handler.run(args)
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def __call__(self, argv=None):
593
except CalledProcessError as error:
594
# Print error.cmd and error.output too?
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raise SystemExit(error.returncode)
596
except KeyboardInterrupt:
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class MainScript(ActionScript):
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"""An `ActionScript` that always accepts a `--config-file` option.
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The `--config-file` option defaults to the value of
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`MAAS_PROVISIONING_SETTINGS` in the process's environment, or absent
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that, `$MAAS_CONFIG_DIR/pserv.yaml` (normally /etc/maas/pserv.yaml for
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packaged installations, or when running from branch, the equivalent
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def __init__(self, description):
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# Avoid circular imports.
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from provisioningserver.config import Config
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super(MainScript, self).__init__(description)
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self.parser.add_argument(
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"-c", "--config-file", metavar="FILENAME",
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help="Configuration file to load [%(default)s].",
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default=Config.DEFAULT_FILENAME)
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class AtomicWriteScript:
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"""Wrap the atomic_write function turning it into an ActionScript.
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>>> main = MainScript(atomic_write.__doc__)
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>>> main.register("myscriptname", AtomicWriteScript)
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def add_arguments(parser):
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"""Initialise options for writing files atomically.
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:param parser: An instance of :class:`ArgumentParser`.
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"--no-overwrite", action="store_true", required=False,
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default=False, help="Don't overwrite file if it exists")
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"--filename", action="store", required=True, help=(
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"The name of the file in which to store contents of stdin"))
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"--mode", action="store", required=False, default=None, help=(
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"They permissions to set on the file. If not set "
647
"will be r/w only to owner"))
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"""Take content from stdin and write it atomically to a file."""
652
content = sys.stdin.read()
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if args.mode is not None:
654
mode = int(args.mode, 8)
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content, args.filename, overwrite=not args.no_overwrite,
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def get_all_interface_addresses():
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"""For each network interface, yield its IPv4 address."""
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for interface in netifaces.interfaces():
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addresses = netifaces.ifaddresses(interface)
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if netifaces.AF_INET in addresses:
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for inet_address in addresses[netifaces.AF_INET]:
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if "addr" in inet_address:
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yield inet_address["addr"]
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def ensure_dir(path):
673
"""Do the equivalent of `mkdir -p`, creating `path` if it didn't exist."""
677
if e.errno != errno.EEXIST:
680
# Path exists, but isn't a directory.
682
# Otherwise, the error is that the directory already existed.
683
# Which is actually success.
687
def tempdir(suffix=b'', prefix=b'maas-', location=None):
688
"""Context manager: temporary directory.
690
Creates a temporary directory (yielding its path, as `unicode`), and
691
cleans it up again when exiting the context.
693
The directory will be readable, writable, and searchable only to the
694
system user who creates it.
696
>>> with tempdir() as playground:
697
... my_file = os.path.join(playground, "my-file")
698
... with open(my_file, 'wb') as handle:
699
... handle.write(b"Hello.\n")
700
... files = os.listdir(playground)
703
>>> os.path.isdir(playground)
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path = tempfile.mkdtemp(suffix, prefix, location)
707
if isinstance(path, bytes):
708
path = path.decode(sys.getfilesystemencoding())
709
assert isinstance(path, unicode)
713
rmtree(path, ignore_errors=True)
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def read_text_file(path, encoding='utf-8'):
717
"""Read and decode the text file at the given path."""
718
with codecs.open(path, encoding=encoding) as infile:
722
def write_text_file(path, text, encoding='utf-8'):
723
"""Write the given unicode text to the given file path.
725
If the file existed, it will be overwritten.
727
with codecs.open(path, 'w', encoding) as outfile:
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def is_compiled_xpath(xpath):
732
"""Is `xpath` a compiled expression?"""
733
return isinstance(xpath, etree.XPath)
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def is_compiled_doc(doc):
737
"""Is `doc` a compiled XPath document evaluator?"""
738
return isinstance(doc, etree.XPathDocumentEvaluator)
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def match_xpath(xpath, doc):
742
"""Return a match of expression `xpath` against document `doc`.
744
:type xpath: Either `unicode` or `etree.XPath`
745
:type doc: Either `etree._ElementTree` or `etree.XPathDocumentEvaluator`
749
is_xpath_compiled = is_compiled_xpath(xpath)
750
is_doc_compiled = is_compiled_doc(doc)
752
if is_xpath_compiled and is_doc_compiled:
753
return doc(xpath.path)
754
elif is_xpath_compiled:
756
elif is_doc_compiled:
759
return doc.xpath(xpath)
762
def try_match_xpath(xpath, doc, logger=logging):
763
"""See if the XPath expression matches the given XML document.
765
Invalid XPath expressions are logged, and are returned as a
768
:type xpath: Either `unicode` or `etree.XPath`
769
:type doc: Either `etree._ElementTree` or `etree.XPathDocumentEvaluator`
774
# Evaluating an XPath expression against a document with LXML
775
# can return a list or a string, and perhaps other types.
776
# Casting the return value into a boolean context appears to
777
# be the most reliable way of detecting a match.
778
return bool(match_xpath(xpath, doc))
779
except etree.XPathEvalError:
780
# Get a plaintext version of `xpath`.
781
expr = xpath.path if is_compiled_xpath(xpath) else xpath
782
logger.exception("Invalid expression: %s", expr)
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def classify(func, subjects):
787
"""Classify `subjects` according to `func`.
789
Splits `subjects` into two lists: one for those which `func`
790
returns a truth-like value, and one for the others.
792
:param subjects: An iterable of `(ident, subject)` tuples, where
793
`subject` is an argument that can be passed to `func` for
795
:param func: A function that takes a single argument.
797
:return: A ``(matched, other)`` tuple, where ``matched`` and
798
``other`` are `list`s of `ident` values; `subject` values are
801
matched, other = [], []
802
for ident, subject in subjects:
803
bucket = matched if func(subject) else other
805
return matched, other
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def find_ip_via_arp(mac):
809
"""Find the IP address for `mac` by reading the output of arp -n.
811
Returns `None` if the MAC is not found.
813
We do this because we aren't necessarily the only DHCP server on the
814
network, so we can't check our own leases file and be guaranteed to find an
817
:param mac: The mac address, e.g. '1c:6f:65:d5:56:98'.
820
output = call_capture_and_check(['arp', '-n']).split('\n')
823
columns = line.split()
824
if len(columns) == 5 and columns[2] == mac:
added
removed
src/provisioningserver/utils/__init__.py
