stevedore/stevedore/dispatch.py
Doug Hellmann 4b3f616eb4 Fix flake8 failures from pull/27
Fix a few formatting issues from within the
previous pull request.

Change-Id: Iadb0d5d4bfa1ac460c730e8af0cfec9386a4c066
2013-09-18 09:43:03 -05:00

202 lines
8.0 KiB
Python

import logging
from .enabled import EnabledExtensionManager
LOG = logging.getLogger(__name__)
class DispatchExtensionManager(EnabledExtensionManager):
"""Loads all plugins and filters on execution.
This is useful for long-running processes that need to pass
different inputs to different extensions.
:param namespace: The namespace for the entry points.
:type namespace: str
:param check_func: Function to determine which extensions to load.
:type check_func: callable
:param invoke_on_load: Boolean controlling whether to invoke the
object returned by the entry point after the driver is loaded.
:type invoke_on_load: bool
:param invoke_args: Positional arguments to pass when invoking
the object returned by the entry point. Only used if invoke_on_load
is True.
:type invoke_args: tuple
:param invoke_kwds: Named arguments to pass when invoking
the object returned by the entry point. Only used if invoke_on_load
is True.
:type invoke_kwds: dict
:param propagate_map_exceptions: Boolean controlling whether exceptions
are propagated up through the map call or whether they are logged and
then ignored
:type invoke_on_load: bool
"""
def map(self, filter_func, func, *args, **kwds):
"""Iterate over the extensions invoking func() for any where
filter_func() returns True.
The signature of filter_func() should be::
def filter_func(ext, *args, **kwds):
pass
The first argument to filter_func(), 'ext', is the
:class:`~stevedore.extension.Extension`
instance. filter_func() should return True if the extension
should be invoked for the input arguments.
The signature for func() should be::
def func(ext, *args, **kwds):
pass
The first argument to func(), 'ext', is the
:class:`~stevedore.extension.Extension` instance.
Exceptions raised from within func() are propagated up and
processing stopped if self.propagate_map_exceptions is True,
otherwise they are logged and ignored.
:param filter_func: Callable to test each extension.
:param func: Callable to invoke for each extension.
:param args: Variable arguments to pass to func()
:param kwds: Keyword arguments to pass to func()
:returns: List of values returned from func()
"""
if not self.extensions:
# FIXME: Use a more specific exception class here.
raise RuntimeError('No %s extensions found' % self.namespace)
response = []
for e in self.extensions:
if filter_func(e, *args, **kwds):
self._invoke_one_plugin(response.append, func, e, args, kwds)
return response
def map_method(self, filter_func, method_name, *args, **kwds):
"""Iterate over the extensions invoking each one's object method called
`method_name` for any where filter_func() returns True.
This is equivalent of using :meth:`map` with func set to
`lambda x: x.obj.method_name()`
while being more convenient.
Exceptions raised from within the called method are propagated up
and processing stopped if self.propagate_map_exceptions is True,
otherwise they are logged and ignored.
.. versionadded:: 0.12
:param filter_func: Callable to test each extension.
:param method_name: The extension method name to call
for each extension.
:param args: Variable arguments to pass to method
:param kwds: Keyword arguments to pass to method
:returns: List of values returned from methods
"""
return self.map(filter_func, self._call_extension_method,
method_name, *args, **kwds)
class NameDispatchExtensionManager(DispatchExtensionManager):
"""Loads all plugins and filters on execution.
This is useful for long-running processes that need to pass
different inputs to different extensions and can predict the name
of the extensions before calling them.
The check_func argument should return a boolean, with ``True``
indicating that the extension should be loaded and made available
and ``False`` indicating that the extension should be ignored.
:param namespace: The namespace for the entry points.
:type namespace: str
:param check_func: Function to determine which extensions to load.
:type check_func: callable
:param invoke_on_load: Boolean controlling whether to invoke the
object returned by the entry point after the driver is loaded.
:type invoke_on_load: bool
:param invoke_args: Positional arguments to pass when invoking
the object returned by the entry point. Only used if invoke_on_load
is True.
:type invoke_args: tuple
:param invoke_kwds: Named arguments to pass when invoking
the object returned by the entry point. Only used if invoke_on_load
is True.
:type invoke_kwds: dict
:param propagate_map_exceptions: Boolean controlling whether exceptions
are propagated up through the map call or whether they are logged and
then ignored
:type invoke_on_load: bool
"""
def __init__(self, namespace, check_func, invoke_on_load=False,
invoke_args=(), invoke_kwds={},
propagate_map_exceptions=False):
super(NameDispatchExtensionManager, self).__init__(
namespace=namespace,
check_func=check_func,
invoke_on_load=invoke_on_load,
invoke_args=invoke_args,
invoke_kwds=invoke_kwds,
propagate_map_exceptions=propagate_map_exceptions,
)
self.by_name = dict((e.name, e) for e in self.extensions)
def map(self, names, func, *args, **kwds):
"""Iterate over the extensions invoking func() for any where
the name is in the given list of names.
The signature for func() should be::
def func(ext, *args, **kwds):
pass
The first argument to func(), 'ext', is the
:class:`~stevedore.extension.Extension` instance.
Exceptions raised from within func() are propagated up and
processing stopped if self.propagate_map_exceptions is True,
otherwise they are logged and ignored.
:param names: List or set of name(s) of extension(s) to invoke.
:param func: Callable to invoke for each extension.
:param args: Variable arguments to pass to func()
:param kwds: Keyword arguments to pass to func()
:returns: List of values returned from func()
"""
response = []
for name in names:
try:
e = self.by_name[name]
except KeyError:
LOG.debug('Missing extension %r being ignored', name)
else:
self._invoke_one_plugin(response.append, func, e, args, kwds)
return response
def map_method(self, names, method_name, *args, **kwds):
"""Iterate over the extensions invoking each one's object method called
`method_name` for any where the name is in the given list of names.
This is equivalent of using :meth:`map` with func set to
`lambda x: x.obj.method_name()`
while being more convenient.
Exceptions raised from within the called method are propagated up
and processing stopped if self.propagate_map_exceptions is True,
otherwise they are logged and ignored.
.. versionadded:: 0.12
:param names: List or set of name(s) of extension(s) to invoke.
:param method_name: The extension method name
to call for each extension.
:param args: Variable arguments to pass to method
:param kwds: Keyword arguments to pass to method
:returns: List of values returned from methods
"""
return self.map(names, self._call_extension_method,
method_name, *args, **kwds)