# taskflow.utils.misc

# Source code for taskflow.utils.misc

    # -*- coding: utf-8 -*-

    #    Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
    #    Copyright (C) 2013 Rackspace Hosting 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.

    import collections
    import contextlib
    import datetime
    import inspect
    import os
    import re
    import socket
    import sys
    import threading
    import types

    import enum
    from oslo_serialization import jsonutils
    from oslo_serialization import msgpackutils
    from oslo_utils import encodeutils
    from oslo_utils import importutils
    from oslo_utils import netutils
    from oslo_utils import reflection
    import six

    from taskflow.types import failure

    UNKNOWN_HOSTNAME = "<unknown>"
    NUMERIC_TYPES = six.integer_types + (float,)

    # NOTE(imelnikov): regular expression to get scheme from URI,
    # see RFC 3986 section 3.1
    _SCHEME_REGEX = re.compile(r"^([A-Za-z][A-Za-z0-9+.-]*):")

    class StrEnum(str, enum.Enum):
        """An enumeration that is also a string and can be compared to strings."""

    class StringIO(six.StringIO):
        """String buffer with some small additions."""

        def write_nl(self, value, linesep=os.linesep):
            self.write(value)
            self.write(linesep)

    class BytesIO(six.BytesIO):
        """Byte buffer with some small additions."""

        def reset(self):
            self.seek(0)
            self.truncate()

    def get_hostname(unknown_hostname=UNKNOWN_HOSTNAME):
        """Gets the machines hostname; if not able to returns an invalid one."""
        try:
            hostname = socket.getfqdn()
            if not hostname:
                return unknown_hostname
            else:
                return hostname
        except socket.error:
            return unknown_hostname

    def match_type(obj, matchers):
        """Matches a given object using the given matchers list/iterable.

        NOTE(harlowja): each element of the provided list/iterable must be
        tuple of (valid types, result).

        Returns the result (the second element of the provided tuple) if a type
        match occurs, otherwise none if no matches are found.
        """
        for (match_types, match_result) in matchers:
            if isinstance(obj, match_types):
                return match_result
        else:
            return None

    def countdown_iter(start_at, decr=1):
        """Generator that decrements after each generation until <= zero.

        NOTE(harlowja): we can likely remove this when we can use an
        ``itertools.count`` that takes a step (on py2.6 which we still support
        that step parameter does **not** exist and therefore can't be used).
        """
        if decr <= 0:
            raise ValueError("Decrement value must be greater"
                             " than zero and not %s" % decr)
        while start_at > 0:
            yield start_at
            start_at -= decr

    def extract_driver_and_conf(conf, conf_key):
        """Common function to get a driver name and its configuration."""
        if isinstance(conf, six.string_types):
            conf = {conf_key: conf}
        maybe_uri = conf[conf_key]
        try:
            uri = parse_uri(maybe_uri)
        except (TypeError, ValueError):
            return (maybe_uri, conf)
        else:
            return (uri.scheme, merge_uri(uri, conf.copy()))

    def reverse_enumerate(items):
        """Like reversed(enumerate(items)) but with less copying/cloning..."""
        for i in countdown_iter(len(items)):
            yield i - 1, items[i - 1]

    def merge_uri(uri, conf):
        """Merges a parsed uri into the given configuration dictionary.

        Merges the username, password, hostname, port, and query parameters of
        a URI into the given configuration dictionary (it does **not** overwrite
        existing configuration keys if they already exist) and returns the merged
        configuration.

        NOTE(harlowja): does not merge the path, scheme or fragment.
        """
        uri_port = uri.port
        specials = [
            ('username', uri.username, lambda v: bool(v)),
            ('password', uri.password, lambda v: bool(v)),
            # NOTE(harlowja): A different check function is used since 0 is
            # false (when bool(v) is applied), and that is a valid port...
            ('port', uri_port, lambda v: v is not None),
        ]
        hostname = uri.hostname
        if hostname:
            if uri_port is not None:
                hostname += ":%s" % (uri_port)
            specials.append(('hostname', hostname, lambda v: bool(v)))
        for (k, v, is_not_empty_value_func) in specials:
            if is_not_empty_value_func(v):
                conf.setdefault(k, v)
        for (k, v) in six.iteritems(uri.params()):
            conf.setdefault(k, v)
        return conf

    def find_subclasses(locations, base_cls, exclude_hidden=True):
        """Finds subclass types in the given locations.

        This will examines the given locations for types which are subclasses of
        the base class type provided and returns the found subclasses (or fails
        with exceptions if this introspection can not be accomplished).

        If a string is provided as one of the locations it will be imported and
        examined if it is a subclass of the base class. If a module is given,
        all of its members will be examined for attributes which are subclasses of
        the base class. If a type itself is given it will be examined for being a
        subclass of the base class.
        """
        derived = set()
        for item in locations:
            module = None
            if isinstance(item, six.string_types):
                try:
                    pkg, cls = item.split(':')
                except ValueError:
                    module = importutils.import_module(item)
                else:
                    obj = importutils.import_class('%s.%s' % (pkg, cls))
                    if not reflection.is_subclass(obj, base_cls):
                        raise TypeError("Object '%s' (%s) is not a '%s' subclass"
                                        % (item, type(item), base_cls))
                    derived.add(obj)
            elif isinstance(item, types.ModuleType):
                module = item
            elif reflection.is_subclass(item, base_cls):
                derived.add(item)
            else:
                raise TypeError("Object '%s' (%s) is an unexpected type" %
                                (item, type(item)))
            # If it's a module derive objects from it if we can.
            if module is not None:
                for (name, obj) in inspect.getmembers(module):
                    if name.startswith("_") and exclude_hidden:
                        continue
                    if reflection.is_subclass(obj, base_cls):
                        derived.add(obj)
        return derived

    def pick_first_not_none(*values):
        """Returns first of values that is *not* None (or None if all are/were)."""
        for val in values:
            if val is not None:
                return val
        return None

    def parse_uri(uri):
        """Parses a uri into its components."""
        # Do some basic validation before continuing...
        if not isinstance(uri, six.string_types):
            raise TypeError("Can only parse string types to uri data, "
                            "and not '%s' (%s)" % (uri, type(uri)))
        match = _SCHEME_REGEX.match(uri)
        if not match:
            raise ValueError("Uri '%s' does not start with a RFC 3986 compliant"
                             " scheme" % (uri))
        return netutils.urlsplit(uri)

    def disallow_when_frozen(excp_cls):
        """Frozen checking/raising method decorator."""

        def decorator(f):

            @six.wraps(f)
            def wrapper(self, *args, **kwargs):
                if self.frozen:
                    raise excp_cls()
                else:
                    return f(self, *args, **kwargs)

            return wrapper

        return decorator

    def clamp(value, minimum, maximum, on_clamped=None):
        """Clamps a value to ensure its >= minimum and <= maximum."""
        if minimum > maximum:
            raise ValueError("Provided minimum '%s' must be less than or equal to"
                             " the provided maximum '%s'" % (minimum, maximum))
        if value > maximum:
            value = maximum
            if on_clamped is not None:
                on_clamped()
        if value < minimum:
            value = minimum
            if on_clamped is not None:
                on_clamped()
        return value

    def fix_newlines(text, replacement=os.linesep):
        """Fixes text that *may* end with wrong nl by replacing with right nl."""
        return replacement.join(text.splitlines())

    def binary_encode(text, encoding='utf-8', errors='strict'):
        """Encodes a text string into a binary string using given encoding.

        Does nothing if data is already a binary string (raises on unknown types).
        """
        if isinstance(text, six.binary_type):
            return text
        else:
            return encodeutils.safe_encode(text, encoding=encoding,
                                           errors=errors)

    def binary_decode(data, encoding='utf-8', errors='strict'):
        """Decodes a binary string into a text string using given encoding.

        Does nothing if data is already a text string (raises on unknown types).
        """
        if isinstance(data, six.text_type):
            return data
        else:
            return encodeutils.safe_decode(data, incoming=encoding,
                                           errors=errors)

    def _check_decoded_type(data, root_types=(dict,)):
        if root_types:
            if not isinstance(root_types, tuple):
                root_types = tuple(root_types)
            if not isinstance(data, root_types):
                if len(root_types) == 1:
                    root_type = root_types[0]
                    raise ValueError("Expected '%s' root type not '%s'"
                                     % (root_type, type(data)))
                else:
                    raise ValueError("Expected %s root types not '%s'"
                                     % (list(root_types), type(data)))
        return data

    def decode_msgpack(raw_data, root_types=(dict,)):
        """Parse raw data to get decoded object.

        Decodes a msgback encoded 'blob' from a given raw data binary string and
        checks that the root type of that decoded object is in the allowed set of
        types (by default a dict should be the root type).
        """
        try:
            data = msgpackutils.loads(raw_data)
        except Exception as e:
            # TODO(harlowja): fix this when msgpackutils exposes the msgpack
            # exceptions so that we can avoid catching just exception...
            raise ValueError("Expected msgpack decodable data: %s" % e)
        else:
            return _check_decoded_type(data, root_types=root_types)

    def decode_json(raw_data, root_types=(dict,)):
        """Parse raw data to get decoded object.

        Decodes a JSON encoded 'blob' from a given raw data binary string and
        checks that the root type of that decoded object is in the allowed set of
        types (by default a dict should be the root type).
        """
        try:
            data = jsonutils.loads(binary_decode(raw_data))
        except UnicodeDecodeError as e:
            raise ValueError("Expected UTF-8 decodable data: %s" % e)
        except ValueError as e:
            raise ValueError("Expected JSON decodable data: %s" % e)
        else:
            return _check_decoded_type(data, root_types=root_types)

    class cachedproperty(object):
        """A *thread-safe* descriptor property that is only evaluated once.

        This caching descriptor can be placed on instance methods to translate
        those methods into properties that will be cached in the instance (avoiding
        repeated attribute checking logic to do the equivalent).

        NOTE(harlowja): by default the property that will be saved will be under
        the decorated methods name prefixed with an underscore. For example if we
        were to attach this descriptor to an instance method 'get_thing(self)' the
        cached property would be stored under '_get_thing' in the self object
        after the first call to 'get_thing' occurs.
        """
        def __init__(self, fget=None, require_lock=True):
            if require_lock:
                self._lock = threading.RLock()
            else:
                self._lock = None
            # If a name is provided (as an argument) then this will be the string
            # to place the cached attribute under if not then it will be the
            # function itself to be wrapped into a property.
            if inspect.isfunction(fget):
                self._fget = fget
                self._attr_name = "_%s" % (fget.__name__)
                self.__doc__ = getattr(fget, '__doc__', None)
            else:
                self._attr_name = fget
                self._fget = None
                self.__doc__ = None

        def __call__(self, fget):
            # If __init__ received a string or a lock boolean then this will be
            # the function to be wrapped as a property (if __init__ got a
            # function then this will not be called).
            self._fget = fget
            if not self._attr_name:
                self._attr_name = "_%s" % (fget.__name__)
            self.__doc__ = getattr(fget, '__doc__', None)
            return self

        def __set__(self, instance, value):
            raise AttributeError("can't set attribute")

        def __delete__(self, instance):
            raise AttributeError("can't delete attribute")

        def __get__(self, instance, owner):
            if instance is None:
                return self
            # Quick check to see if this already has been made (before acquiring
            # the lock). This is safe to do since we don't allow deletion after
            # being created.
            if hasattr(instance, self._attr_name):
                return getattr(instance, self._attr_name)
            else:
                if self._lock is not None:
                    self._lock.acquire()
                try:
                    return getattr(instance, self._attr_name)
                except AttributeError:
                    value = self._fget(instance)
                    setattr(instance, self._attr_name, value)
                    return value
                finally:
                    if self._lock is not None:
                        self._lock.release()

    def millis_to_datetime(milliseconds):
        """Converts number of milliseconds (from epoch) into a datetime object."""
        return datetime.datetime.fromtimestamp(float(milliseconds) / 1000)

    def get_version_string(obj):
        """Gets a object's version as a string.

        Returns string representation of object's version taken from
        its 'version' attribute, or None if object does not have such
        attribute or its version is None.
        """
        obj_version = getattr(obj, 'version', None)
        if isinstance(obj_version, (list, tuple)):
            obj_version = '.'.join(str(item) for item in obj_version)
        if obj_version is not None and not isinstance(obj_version,
                                                      six.string_types):
            obj_version = str(obj_version)
        return obj_version

    def sequence_minus(seq1, seq2):
        """Calculate difference of two sequences.

        Result contains the elements from first sequence that are not
        present in second sequence, in original order. Works even
        if sequence elements are not hashable.
        """
        result = list(seq1)
        for item in seq2:
            try:
                result.remove(item)
            except ValueError:
                pass
        return result

    def as_int(obj, quiet=False):
        """Converts an arbitrary value into a integer."""
        # Try "2" -> 2
        try:
            return int(obj)
        except (ValueError, TypeError):
            pass
        # Try "2.5" -> 2
        try:
            return int(float(obj))
        except (ValueError, TypeError):
            pass
        # Eck, not sure what this is then.
        if not quiet:
            raise TypeError("Can not translate '%s' (%s) to an integer"
                            % (obj, type(obj)))
        return obj

    @contextlib.contextmanager
    def capture_failure():
        """Captures the occurring exception and provides a failure object back.

        This will save the current exception information and yield back a
        failure object for the caller to use (it will raise a runtime error if
        no active exception is being handled).

        This is useful since in some cases the exception context can be cleared,
        resulting in None being attempted to be saved after an exception handler is
        run. This can happen when eventlet switches greenthreads or when running an
        exception handler, code raises and catches an exception. In both
        cases the exception context will be cleared.

        To work around this, we save the exception state, yield a failure and
        then run other code.

        For example::

            >>> from taskflow.utils import misc
            >>>
            >>> def cleanup():
            ...     pass
            ...
            >>>
            >>> def save_failure(f):
            ...     print("Saving %s" % f)
            ...
            >>>
            >>> try:
            ...     raise IOError("Broken")
            ... except Exception:
            ...     with misc.capture_failure() as fail:
            ...         print("Activating cleanup")
            ...         cleanup()
            ...         save_failure(fail)
            ...
            Activating cleanup
            Saving Failure: IOError: Broken

        """
        exc_info = sys.exc_info()
        if not any(exc_info):
            raise RuntimeError("No active exception is being handled")
        else:
            yield failure.Failure(exc_info=exc_info)

    def is_iterable(obj):
        """Tests an object to to determine whether it is iterable.

        This function will test the specified object to determine whether it is
        iterable. String types (both ``str`` and ``unicode``) are ignored and will
        return False.

        :param obj: object to be tested for iterable
        :return: True if object is iterable and is not a string
        """
        return (not isinstance(obj, six.string_types) and
                isinstance(obj, collections.Iterable))

    def safe_copy_dict(obj):
        """Copy an existing dictionary or default to empty dict...

        This will return a empty dict if given object is falsey, otherwise it
        will create a dict of the given object (which if provided a dictionary
        object will make a shallow copy of that object).
        """
        if not obj:
            return {}
        # default to a shallow copy to avoid most ownership issues
        return dict(obj)

this page last updated: 2020-04-10 14:06:26

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