utils.py

# Copyright 2016 NTT DATA
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

"""Utilities and helper functions."""

import contextlib
import functools
import inspect
import pyclbr
import shutil
import sys
import tempfile

import eventlet
from oslo_concurrency import lockutils
from oslo_context import context as common_context
from oslo_log import log as logging
from oslo_utils import importutils
from oslo_utils import strutils
from oslo_utils import timeutils

import masakari.conf
from masakari import exception
from masakari.i18n import _
from masakari import safe_utils


CONF = masakari.conf.CONF

LOG = logging.getLogger(__name__)


def reraise(tp, value, tb=None):
    try:
        if value is None:
            value = tp()
        if value.__traceback__ is not tb:
            raise value.with_traceback(tb)
        raise value
    finally:
        value = None
        tb = None


def utf8(value):
    """Try to turn a string into utf-8 if possible.

    The original code was copied from the utf8 function in
    http://github.com/facebook/tornado/blob/master/tornado/escape.py

    """
    if value is None or isinstance(value, bytes):
        return value

    if not isinstance(value, str):
        value = str(value)

    return value.encode('utf-8')


def check_isinstance(obj, cls):
    """Checks that obj is of type cls, and lets PyLint infer types."""
    if isinstance(obj, cls):
        return obj
    raise Exception(_('Expected object of type: %s') % (str(cls)))


def monkey_patch():
    """If the CONF.monkey_patch set as True,
    this function patches a decorator
    for all functions in specified modules.
    You can set decorators for each modules
    using CONF.monkey_patch_modules.
    The format is "Module path:Decorator function".

    name - name of the function
    function - object of the function
    """
    # If CONF.monkey_patch is not True, this function do nothing.
    if not CONF.monkey_patch:
        return

    def is_method(obj):
        # Unbound methods became regular functions on Python 3
        return inspect.ismethod(obj) or inspect.isfunction(obj)

    # Get list of modules and decorators
    for module_and_decorator in CONF.monkey_patch_modules:
        module, decorator_name = module_and_decorator.split(':')
        # import decorator function
        decorator = importutils.import_class(decorator_name)
        __import__(module)
        # Retrieve module information using pyclbr
        module_data = pyclbr.readmodule_ex(module)
        for key, value in module_data.items():
            # set the decorator for the class methods
            if isinstance(value, pyclbr.Class):
                clz = importutils.import_class("%s.%s" % (module, key))
                for method, func in inspect.getmembers(clz, is_method):
                    setattr(clz, method,
                            decorator("%s.%s.%s" % (module, key,
                                                    method), func))
            # set the decorator for the function
            if isinstance(value, pyclbr.Function):
                func = importutils.import_class("%s.%s" % (module, key))
                setattr(sys.modules[module], key,
                        decorator("%s.%s" % (module, key), func))


def walk_class_hierarchy(clazz, encountered=None):
    """Walk class hierarchy, yielding most derived classes first."""
    if not encountered:
        encountered = []
    for subclass in clazz.__subclasses__():
        if subclass not in encountered:
            encountered.append(subclass)
            # drill down to leaves first
            for subsubclass in walk_class_hierarchy(subclass, encountered):
                yield subsubclass
            yield subclass


def expects_func_args(*args):
    def _decorator_checker(dec):
        @functools.wraps(dec)
        def _decorator(f):
            base_f = safe_utils.get_wrapped_function(f)
            arg_names, a, kw, _, _, _, _ = inspect.getfullargspec(base_f)
            if a or kw or set(args) <= set(arg_names):
                # NOTE : We can't really tell if correct stuff will
                # be passed if it's a function with *args or **kwargs so
                # we still carry on and hope for the best
                return dec(f)
            else:
                raise TypeError("Decorated function %(f_name)s does not "
                                "have the arguments expected by the "
                                "decorator %(d_name)s" %
                                {'f_name': base_f.__name__,
                                 'd_name': dec.__name__})
        return _decorator
    return _decorator_checker


def isotime(at=None):
    """Current time as ISO string,
    as timeutils.isotime() is deprecated

    :returns: Current time in ISO format
    """
    if not at:
        at = timeutils.utcnow()
    date_string = at.strftime("%Y-%m-%dT%H:%M:%S")
    tz = at.tzinfo.tzname(None) if at.tzinfo else 'UTC'
    date_string += ('Z' if tz in ['UTC', 'UTC+00:00'] else tz)
    return date_string


def strtime(at):
    return at.strftime("%Y-%m-%dT%H:%M:%S.%f")


class ExceptionHelper(object):
    """Class to wrap another and translate the ClientExceptions raised by its
    function calls to the actual ones.
    """

    def __init__(self, target):
        self._target = target

    def __getattr__(self, name):
        func = getattr(self._target, name)

        @functools.wraps(func)
        def wrapper(*args, **kwargs):
            try:
                return func(*args, **kwargs)
            except Exception as e:
                reraise(*e.exc_info)
        return wrapper


def spawn(func, *args, **kwargs):
    """Passthrough method for eventlet.spawn.

    This utility exists so that it can be stubbed for testing without
    interfering with the service spawns.

    It will also grab the context from the threadlocal store and add it to
    the store on the new thread.  This allows for continuity in logging the
    context when using this method to spawn a new thread.
    """
    _context = common_context.get_current()

    @functools.wraps(func)
    def context_wrapper(*args, **kwargs):
        # NOTE: If update_store is not called after spawn it won't be
        # available for the logger to pull from threadlocal storage.
        if _context is not None:
            _context.update_store()
        return func(*args, **kwargs)

    return eventlet.spawn(context_wrapper, *args, **kwargs)


def spawn_n(func, *args, **kwargs):
    """Passthrough method for eventlet.spawn_n.

    This utility exists so that it can be stubbed for testing without
    interfering with the service spawns.

    It will also grab the context from the threadlocal store and add it to
    the store on the new thread.  This allows for continuity in logging the
    context when using this method to spawn a new thread.
    """
    _context = common_context.get_current()

    @functools.wraps(func)
    def context_wrapper(*args, **kwargs):
        # NOTE: If update_store is not called after spawn_n it won't be
        # available for the logger to pull from threadlocal storage.
        if _context is not None:
            _context.update_store()
        func(*args, **kwargs)

    eventlet.spawn_n(context_wrapper, *args, **kwargs)


@contextlib.contextmanager
def tempdir(**kwargs):
    argdict = kwargs.copy()
    if 'dir' not in argdict:
        argdict['dir'] = CONF.tempdir
    tmpdir = tempfile.mkdtemp(**argdict)
    try:
        yield tmpdir
    finally:
        try:
            shutil.rmtree(tmpdir)
        except OSError as e:
            LOG.error('Could not remove tmpdir: %s', e)


def validate_integer(value, name, min_value=None, max_value=None):
    """Make sure that value is a valid integer, potentially within range."""
    try:
        return strutils.validate_integer(value, name, min_value, max_value)
    except ValueError as e:
        raise exception.InvalidInput(reason=e)


def synchronized(name, semaphores=None, blocking=False):
    def wrap(f):
        @functools.wraps(f)
        def inner(*args, **kwargs):
            lock_name = 'masakari-%s' % name
            int_lock = lockutils.internal_lock(lock_name,
                                               semaphores=semaphores)
            LOG.debug("Acquiring lock: %(lock_name)s on resource: "
                      "%(resource)s", {'lock_name': lock_name,
                                       'resource': f.__name__})

            if not int_lock.acquire(blocking=blocking):
                raise exception.LockAlreadyAcquired(resource=name)
            try:
                return f(*args, **kwargs)
            finally:
                LOG.debug("Releasing lock: %(lock_name)s on resource: "
                          "%(resource)s", {'lock_name': lock_name,
                                           'resource': f.__name__})
                int_lock.release()
        return inner
    return wrap