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OpenStack Study: base.py**** CubicPower OpenStack Study ****
# vim: tabstop=4 shiftwidth=4 softtabstop=4 # Copyright 2012 Nebula, Inc. # # 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 copy import inspect import logging from django.core import urlresolvers from django import forms from django.forms.forms import NON_FIELD_ERRORS # noqa from django import template from django.template.defaultfilters import linebreaks # noqa from django.template.defaultfilters import safe # noqa from django.template.defaultfilters import slugify # noqa from django.utils.encoding import force_unicode from django.utils.importlib import import_module # noqa from django.utils.translation import ugettext_lazy as _ from horizon import base from horizon import exceptions from horizon.templatetags.horizon import has_permissions # noqa from horizon.utils import html LOG = logging.getLogger(__name__)
**** CubicPower OpenStack Study **** class WorkflowContext(dict):
**** CubicPower OpenStack Study **** def __init__(self, workflow, *args, **kwargs): super(WorkflowContext, self).__init__(*args, **kwargs) self._workflow = workflow
**** CubicPower OpenStack Study **** def __setitem__(self, key, val): super(WorkflowContext, self).__setitem__(key, val) return self._workflow._trigger_handlers(key)
**** CubicPower OpenStack Study **** def __delitem__(self, key): return self.__setitem__(key, None)
**** CubicPower OpenStack Study **** def set(self, key, val): return self.__setitem__(key, val)
**** CubicPower OpenStack Study **** def unset(self, key): return self.__delitem__(key)
**** CubicPower OpenStack Study **** class ActionMetaclass(forms.forms.DeclarativeFieldsMetaclass):
**** CubicPower OpenStack Study **** def __new__(mcs, name, bases, attrs): # Pop Meta for later processing opts = attrs.pop("Meta", None) # Create our new class cls = super(ActionMetaclass, mcs).__new__(mcs, name, bases, attrs) # Process options from Meta cls.name = getattr(opts, "name", name) cls.slug = getattr(opts, "slug", slugify(name)) cls.permissions = getattr(opts, "permissions", ()) cls.progress_message = getattr(opts, "progress_message", _("Processing...")) cls.help_text = getattr(opts, "help_text", "") cls.help_text_template = getattr(opts, "help_text_template", None) return cls
**** CubicPower OpenStack Study **** class Action(forms.Form): """An ``Action`` represents an atomic logical interaction you can have with the system. This is easier to understand with a conceptual example: in the context of a "launch instance" workflow, actions would include "naming the instance", "selecting an image", and ultimately "launching the instance". Because ``Actions`` are always interactive, they always provide form controls, and thus inherit from Django's ``Form`` class. However, they have some additional intelligence added to them: * ``Actions`` are aware of the permissions required to complete them. * ``Actions`` have a meta-level concept of "help text" which is meant to be displayed in such a way as to give context to the action regardless of where the action is presented in a site or workflow. * ``Actions`` understand how to handle their inputs and produce outputs, much like :class:`~horizon.forms.SelfHandlingForm` does now. ``Action`` classes may
**** CubicPower OpenStack Study **** def __init__(self, request, context, *args, **kwargs): if request.method == "POST": super(Action, self).__init__(request.POST, initial=context) else: super(Action, self).__init__(initial=context) if not hasattr(self, "handle"): raise AttributeError("The action %s must define a handle method." % self.__class__.__name__) self.request = request self._populate_choices(request, context) self.required_css_class = 'required'
**** CubicPower OpenStack Study **** def __unicode__(self): return force_unicode(self.name)
**** CubicPower OpenStack Study **** def __repr__(self): return "<%s: %s>" % (self.__class__.__name__, self.slug)
**** CubicPower OpenStack Study **** def _populate_choices(self, request, context): for field_name, bound_field in self.fields.items(): meth = getattr(self, "populate_%s_choices" % field_name, None) if meth is not None and callable(meth): bound_field.choices = meth(request, context)
**** CubicPower OpenStack Study **** def get_help_text(self, extra_context=None): """Returns the help text for this step.""" text = "" extra_context = extra_context or {} if self.help_text_template: tmpl = template.loader.get_template(self.help_text_template) context = template.RequestContext(self.request, extra_context) text += tmpl.render(context) else: text += linebreaks(force_unicode(self.help_text)) return safe(text)
**** CubicPower OpenStack Study **** def add_error(self, message): """Adds an error to the Action's Step based on API issues.""" self.errors[NON_FIELD_ERRORS] = self.error_class([message])
**** CubicPower OpenStack Study **** def handle(self, request, context): """Handles any requisite processing for this action. The method should return either ``None`` or a dictionary of data to be passed to :meth:`~horizon.workflows.Step.contribute`. Returns ``None`` by default, effectively making it a no-op. """ return None
**** CubicPower OpenStack Study **** class MembershipAction(Action): """An action that allows a user to add/remove members from a group. Extend the Action class with additional helper method for membership management. """
**** CubicPower OpenStack Study **** def get_default_role_field_name(self): return "default_" + self.slug + "_role"
**** CubicPower OpenStack Study **** def get_member_field_name(self, role_id): return self.slug + "_role_" + role_id
**** CubicPower OpenStack Study **** class Step(object): """A step is a wrapper around an action which
**** CubicPower OpenStack Study **** def __repr__(self): return "<%s: %s>" % (self.__class__.__name__, self.slug)
**** CubicPower OpenStack Study **** def __unicode__(self): return force_unicode(self.name)
**** CubicPower OpenStack Study **** def __init__(self, workflow): super(Step, self).__init__() self.workflow = workflow cls = self.__class__.__name__ if not (self.action_class and issubclass(self.action_class, Action)): raise AttributeError("You must specify an action for %s." % cls) self.slug = self.action_class.slug self.name = self.action_class.name self.permissions = self.action_class.permissions self.has_errors = False self._handlers = {} if self.connections is None: # We want a dict, but don't want to declare a mutable type on the # class directly. self.connections = {} # Gather our connection handlers and make sure they exist. for key, handlers in self.connections.items(): self._handlers[key] = [] # TODO(gabriel): This is a poor substitute for broader handling if not isinstance(handlers, (list, tuple)): raise TypeError("The connection handlers for %s must be a " "list or tuple." % cls) for possible_handler in handlers: if callable(possible_handler): # If it's callable we know the function exists and is valid self._handlers[key].append(possible_handler) continue elif not isinstance(possible_handler, basestring): return TypeError("Connection handlers must be either " "callables or strings.") bits = possible_handler.split(".") if bits[0] == "self": root = self for bit in bits[1:]: try: root = getattr(root, bit) except AttributeError: raise AttributeError("The connection handler %s " "could not be found on %s." % (possible_handler, cls)) handler = root elif len(bits) == 1: # Import by name from local module not supported raise ValueError("Importing a local function as a string " "is not supported for the connection " "handler %s on %s." % (possible_handler, cls)) else: # Try a general import module_name = ".".join(bits[:-1]) try: mod = import_module(module_name) handler = getattr(mod, bits[-1]) except ImportError: raise ImportError("Could not import %s from the " "module %s as a connection " "handler on %s." % (bits[-1], module_name, cls)) except AttributeError: raise AttributeError("Could not import %s from the " "module %s as a connection " "handler on %s." % (bits[-1], module_name, cls)) self._handlers[key].append(handler) @property
**** CubicPower OpenStack Study **** def action(self): if not getattr(self, "_action", None): try: # Hook in the action context customization. workflow_context = dict(self.workflow.context) context = self.prepare_action_context(self.workflow.request, workflow_context) self._action = self.action_class(self.workflow.request, context) except Exception: LOG.exception("Problem instantiating action class.") raise return self._action
**** CubicPower OpenStack Study **** def prepare_action_context(self, request, context): """Allows for customization of how the workflow context is passed to the action; this is the reverse of what "contribute" does to make the action outputs sane for the workflow. Changes to the context are not saved globally here. They are localized to the action. Simply returns the unaltered context by default. """ return context
**** CubicPower OpenStack Study **** def get_id(self): """Returns the ID for this step. Suitable for use in HTML markup.""" return "%s__%s" % (self.workflow.slug, self.slug)
**** CubicPower OpenStack Study **** def _verify_contributions(self, context): for key in self.contributes: # Make sure we don't skip steps based on weird behavior of # POST query dicts. field = self.action.fields.get(key, None) if field and field.required and not context.get(key): context.pop(key, None) failed_to_contribute = set(self.contributes) failed_to_contribute -= set(context.keys()) if failed_to_contribute: raise exceptions.WorkflowError("The following expected data was " "not added to the workflow context " "by the step %s: %s." % (self.__class__, failed_to_contribute)) return True
**** CubicPower OpenStack Study **** def contribute(self, data, context): """Adds the data listed in ``contributes`` to the workflow's shared context. By default, the context is simply updated with all the data returned by the action. Note that even if the value of one of the ``contributes`` keys is not present (e.g. optional) the key should still be added to the context with a value of ``None``. """ if data: for key in self.contributes: context[key] = data.get(key, None) return context
**** CubicPower OpenStack Study **** def render(self): """Renders the step.""" step_template = template.loader.get_template(self.template_name) extra_context = {"form": self.action, "step": self} context = template.RequestContext(self.workflow.request, extra_context) return step_template.render(context)
**** CubicPower OpenStack Study **** def get_help_text(self): """Returns the help text for this step.""" text = linebreaks(force_unicode(self.help_text)) text += self.action.get_help_text() return safe(text)
**** CubicPower OpenStack Study **** def add_error(self, message): """Adds an error to the Step based on API issues.""" self.action.add_error(message)
**** CubicPower OpenStack Study **** def has_required_fields(self): """Returns True if action contains any required fields.""" return any(field.required for field in self.action.fields.values())
**** CubicPower OpenStack Study **** class WorkflowMetaclass(type):
**** CubicPower OpenStack Study **** def __new__(mcs, name, bases, attrs): super(WorkflowMetaclass, mcs).__new__(mcs, name, bases, attrs) attrs["_cls_registry"] = set([]) return type.__new__(mcs, name, bases, attrs)
**** CubicPower OpenStack Study **** class UpdateMembersStep(Step): """A step that allows a user to add/remove members from a group. .. attribute:: show_roles Set to False to disable the display of the roles dropdown. .. attribute:: available_list_title The title used for the available list column. .. attribute:: members_list_title The title used for the members list column. .. attribute:: no_available_text The placeholder text used when the available list is empty. .. attribute:: no_members_text The placeholder text used when the members list is empty. """ template_name = "horizon/common/_workflow_step_update_members.html" show_roles = True available_list_title = _("All available") members_list_title = _("Members") no_available_text = _("None available.") no_members_text = _("No members.")
**** CubicPower OpenStack Study **** def get_member_field_name(self, role_id): if issubclass(self.action_class, MembershipAction): return self.action.get_member_field_name(role_id) else: return self.slug + "_role_" + role_id
**** CubicPower OpenStack Study **** class Workflow(html.HTMLElement): """A Workflow is a collection of Steps. Its interface is very straightforward, but it is responsible for handling some very important tasks such as: * Handling the injection, removal, and ordering of arbitrary steps. * Determining if the workflow can be completed by a given user at runtime based on all available information. * Dispatching connections between steps to ensure that when context data changes all the applicable callback functions are executed. * Verifying/validating the overall data integrity and subsequently triggering the final method to complete the workflow. The ``Workflow`` class has the following attributes: .. attribute:: name The verbose name for this workflow which will be displayed to the user. Defaults to the class name. .. attribute:: slug The unique slug for this workflow. Required. .. attribute:: steps Read-only access to the final ordered set of step instances for this workflow. .. attribute::
**** CubicPower OpenStack Study **** def __unicode__(self): return self.name
**** CubicPower OpenStack Study **** def __repr__(self): return "<%s: %s>" % (self.__class__.__name__, self.slug)
**** CubicPower OpenStack Study **** def __init__(self, request=None, context_seed=None, entry_point=None, *args, **kwargs): super(Workflow, self).__init__(*args, **kwargs) if self.slug is None: raise AttributeError("The workflow %s must have a slug." % self.__class__.__name__) self.name = getattr(self, "name", self.__class__.__name__) self.request = request self.depends_on = set([]) self.contributions = set([]) self.entry_point = entry_point self.object = None # Put together our steps in order. Note that we pre-register # non-default steps so that we can identify them and subsequently # insert them in order correctly. self._registry = dict([(step_class, step_class(self)) for step_class in self.__class__._cls_registry if step_class not in self.default_steps]) self._gather_steps() # Determine all the context data we need to end up with. for step in self.steps: self.depends_on = self.depends_on | set(step.depends_on) self.contributions = self.contributions | set(step.contributes) # Initialize our context. For ease we can preseed it with a # regular dictionary. This should happen after steps have been # registered and ordered. self.context = WorkflowContext(self) context_seed = context_seed or {} clean_seed = dict([(key, val) for key, val in context_seed.items() if key in self.contributions | self.depends_on]) self.context_seed = clean_seed self.context.update(clean_seed) if request and request.method == "POST": for step in self.steps: valid = step.action.is_valid() # Be sure to use the CLEANED data if the workflow is valid. if valid: data = step.action.cleaned_data else: data = request.POST self.context = step.contribute(data, self.context) @property
**** CubicPower OpenStack Study **** def steps(self): if getattr(self, "_ordered_steps", None) is None: self._gather_steps() return self._ordered_steps
**** CubicPower OpenStack Study **** def get_step(self, slug): """Returns the instantiated step matching the given slug.""" for step in self.steps: if step.slug == slug: return step
**** CubicPower OpenStack Study **** def _gather_steps(self): ordered_step_classes = self._order_steps() for default_step in self.default_steps: self.register(default_step) self._registry[default_step] = default_step(self) self._ordered_steps = [self._registry[step_class] for step_class in ordered_step_classes if has_permissions(self.request.user, self._registry[step_class])]
**** CubicPower OpenStack Study **** def _order_steps(self): steps = list(copy.copy(self.default_steps)) additional = self._registry.keys() for step in additional: try: min_pos = steps.index(step.after) except ValueError: min_pos = 0 try: max_pos = steps.index(step.before) except ValueError: max_pos = len(steps) if min_pos > max_pos: raise exceptions.WorkflowError("The step %(new)s can't be " "placed between the steps " "%(after)s and %(before)s; the " "step %(before)s comes before " "%(after)s." % {"new": additional, "after": step.after, "before": step.before}) steps.insert(max_pos, step) return steps
**** CubicPower OpenStack Study **** def get_entry_point(self): """Returns the slug of the step which the workflow should begin on. This method takes into account both already-available data and errors within the steps. """ # If we have a valid specified entry point, use it. if self.entry_point: if self.get_step(self.entry_point): return self.entry_point # Otherwise fall back to calculating the appropriate entry point. for step in self.steps: if step.has_errors: return step.slug try: step._verify_contributions(self.context) except exceptions.WorkflowError: return step.slug # If nothing else, just return the first step. return self.steps[0].slug
**** CubicPower OpenStack Study **** def _trigger_handlers(self, key): responses = [] handlers = [(step.slug, f) for step in self.steps for f in step._handlers.get(key, [])] for slug, handler in handlers: responses.append((slug, handler(self.request, self.context))) return responses @classmethod
**** CubicPower OpenStack Study **** def register(cls, step_class): """Registers a :class:`~horizon.workflows.Step` with the workflow.""" if not inspect.isclass(step_class): raise ValueError('Only classes may be registered.') elif not issubclass(step_class, cls._registerable_class): raise ValueError('Only %s classes or subclasses may be registered.' % cls._registerable_class.__name__) if step_class in cls._cls_registry: return False else: cls._cls_registry.add(step_class) return True @classmethod
**** CubicPower OpenStack Study **** def unregister(cls, step_class): """Unregisters a :class:`~horizon.workflows.Step` from the workflow. """ try: cls._cls_registry.remove(step_class) except KeyError: raise base.NotRegistered('%s is not registered' % cls) return cls._unregister(step_class)
**** CubicPower OpenStack Study **** def validate(self, context): """Hook for custom context data validation. Should return a boolean value or raise :class:`~horizon.exceptions.WorkflowValidationError`. """ return True
**** CubicPower OpenStack Study **** def is_valid(self): """Verified that all required data is present in the context and calls the ``validate`` method to allow for finer-grained checks on the context data. """ missing = self.depends_on - set(self.context.keys()) if missing: raise exceptions.WorkflowValidationError( "Unable to complete the workflow. The values %s are " "required but not present." % ", ".join(missing)) # Validate each step. Cycle through all of them to catch all errors # in one pass before returning. steps_valid = True for step in self.steps: if not step.action.is_valid(): steps_valid = False step.has_errors = True if not steps_valid: return steps_valid return self.validate(self.context)
**** CubicPower OpenStack Study **** def finalize(self): """Finalizes a workflow by running through all the actions in order and calling their ``handle`` methods. Returns ``True`` on full success, or ``False`` for a partial success, e.g. there were non-critical errors. (If it failed completely the function wouldn't return.) """ partial = False for step in self.steps: try: data = step.action.handle(self.request, self.context) if data is True or data is None: continue elif data is False: partial = True else: self.context = step.contribute(data or {}, self.context) except Exception: partial = True exceptions.handle(self.request) if not self.handle(self.request, self.context): partial = True return not partial
**** CubicPower OpenStack Study **** def handle(self, request, context): """Handles any final processing for this workflow. Should return a boolean value indicating success. """ return True
**** CubicPower OpenStack Study **** def get_success_url(self): """Returns a URL to redirect the user to upon completion. By default it will attempt to parse a ``success_url`` attribute on the workflow, which can take the form of a reversible URL pattern name, or a standard HTTP URL. """ try: return urlresolvers.reverse(self.success_url) except urlresolvers.NoReverseMatch: return self.success_url
**** CubicPower OpenStack Study **** def format_status_message(self, message): """Hook to allow customization of the message returned to the user upon successful or unsuccessful completion of the workflow. By default it simply inserts the workflow's name into the message string. """ if "%s" in message: return message % self.name else: return message
**** CubicPower OpenStack Study **** def render(self): """Renders the workflow.""" workflow_template = template.loader.get_template(self.template_name) extra_context = {"workflow": self} if self.request.is_ajax(): extra_context['modal'] = True context = template.RequestContext(self.request, extra_context) return workflow_template.render(context)
**** CubicPower OpenStack Study **** def get_absolute_url(self): """Returns the canonical URL for this workflow. This is used for the POST action attribute on the form element wrapping the workflow. For convenience it defaults to the value of ``request.get_full_path()`` with any query string stripped off, e.g. the path at which the workflow was requested. """ return self.request.get_full_path().partition('?')[0]
**** CubicPower OpenStack Study **** def add_error_to_step(self, message, slug): """Adds an error to the workflow's Step with the specified slug based on API issues. This is useful when you wish for API errors to appear as errors on the form rather than using the messages framework. """ step = self.get_step(slug) if step: step.add_error(message)
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