126 lines
4.5 KiB
Python
126 lines
4.5 KiB
Python
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from charmhelpers.core import hookenv
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from charmhelpers.core import templating
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from charmhelpers.core.services.base import ManagerCallback
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__all__ = ['RelationContext', 'TemplateCallback',
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'render_template', 'template']
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class RelationContext(dict):
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"""
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Base class for a context generator that gets relation data from juju.
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Subclasses must provide the attributes `name`, which is the name of the
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interface of interest, `interface`, which is the type of the interface of
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interest, and `required_keys`, which is the set of keys required for the
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relation to be considered complete. The data for all interfaces matching
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the `name` attribute that are complete will used to populate the dictionary
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values (see `get_data`, below).
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The generated context will be namespaced under the interface type, to prevent
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potential naming conflicts.
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"""
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name = None
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interface = None
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required_keys = []
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def __init__(self, *args, **kwargs):
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super(RelationContext, self).__init__(*args, **kwargs)
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self.get_data()
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def __bool__(self):
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"""
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Returns True if all of the required_keys are available.
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"""
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return self.is_ready()
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__nonzero__ = __bool__
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def __repr__(self):
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return super(RelationContext, self).__repr__()
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def is_ready(self):
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"""
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Returns True if all of the `required_keys` are available from any units.
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"""
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ready = len(self.get(self.name, [])) > 0
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if not ready:
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hookenv.log('Incomplete relation: {}'.format(self.__class__.__name__), hookenv.DEBUG)
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return ready
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def _is_ready(self, unit_data):
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"""
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Helper method that tests a set of relation data and returns True if
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all of the `required_keys` are present.
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"""
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return set(unit_data.keys()).issuperset(set(self.required_keys))
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def get_data(self):
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"""
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Retrieve the relation data for each unit involved in a relation and,
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if complete, store it in a list under `self[self.name]`. This
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is automatically called when the RelationContext is instantiated.
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The units are sorted lexographically first by the service ID, then by
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the unit ID. Thus, if an interface has two other services, 'db:1'
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and 'db:2', with 'db:1' having two units, 'wordpress/0' and 'wordpress/1',
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and 'db:2' having one unit, 'mediawiki/0', all of which have a complete
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set of data, the relation data for the units will be stored in the
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order: 'wordpress/0', 'wordpress/1', 'mediawiki/0'.
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If you only care about a single unit on the relation, you can just
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access it as `{{ interface[0]['key'] }}`. However, if you can at all
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support multiple units on a relation, you should iterate over the list,
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like::
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{% for unit in interface -%}
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{{ unit['key'] }}{% if not loop.last %},{% endif %}
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{%- endfor %}
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Note that since all sets of relation data from all related services and
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units are in a single list, if you need to know which service or unit a
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set of data came from, you'll need to extend this class to preserve
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that information.
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"""
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if not hookenv.relation_ids(self.name):
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return
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ns = self.setdefault(self.name, [])
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for rid in sorted(hookenv.relation_ids(self.name)):
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for unit in sorted(hookenv.related_units(rid)):
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reldata = hookenv.relation_get(rid=rid, unit=unit)
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if self._is_ready(reldata):
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ns.append(reldata)
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def provide_data(self):
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"""
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Return data to be relation_set for this interface.
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"""
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return {}
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class TemplateCallback(ManagerCallback):
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"""
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Callback class that will render a template, for use as a ready action.
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"""
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def __init__(self, source, target, owner='root', group='root', perms=0444):
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self.source = source
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self.target = target
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self.owner = owner
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self.group = group
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self.perms = perms
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def __call__(self, manager, service_name, event_name):
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service = manager.get_service(service_name)
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context = {}
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for ctx in service.get('required_data', []):
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context.update(ctx)
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templating.render(self.source, self.target, context,
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self.owner, self.group, self.perms)
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# Convenience aliases for templates
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render_template = template = TemplateCallback
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