requires.md

class PrometheusManualRequires(ResponderEndpoint)

Base class for Endpoints that respond to requests in the request / response pattern.

Subclasses must set the REQUEST_CLASS attribute to a subclass of :class:BaseRequest which defines the fields the request will use.

all_departed_units

Collection of all units that were previously part of any relation on this endpoint but which have since departed.

This collection is persistent and mutable. The departed units will be kept until they are explicitly removed, to allow for reasonable cleanup of units that have left.

Example: You need to run a command each time a unit departs the relation.

.. code-block:: python

@when('endpoint.{endpoint_name}.departed')
def handle_departed_unit(self):
    for name, unit in self.all_departed_units.items():
        # run the command to remove `unit` from the cluster
        #  ..
    self.all_departed_units.clear()
    clear_flag(self.expand_name('departed'))

Once a unit is departed, it will no longer show up in :attr:all_joined_units. Note that units are considered departed as soon as the departed hook is entered, which differs slightly from how the Juju primitives behave (departing units are still returned from related-units until after the departed hook is complete).

This collection is a :class:KeyList, so can be used as a mapping to look up units by their unit name, or iterated or accessed by index.

all_joined_units

A list view of all the units of all relations attached to this :class:~charms.reactive.endpoints.Endpoint.

This is actually a :class:~charms.reactive.endpoints.CombinedUnitsView, so the units will be in order by relation ID and then unit name, and you can access a merged view of all the units' data as a single mapping. You should be very careful when using the merged data collections, however, and consider carefully what will happen when the endpoint has multiple relations and multiple remote units on each. It is probably better to iterate over each unit and handle its data individually. See :class:~charms.reactive.endpoints.CombinedUnitsView for an explanation of how the merged data collections work.

Note that, because a given application might be related multiple times on a given endpoint, units may show up in this collection more than once.

all_requests

A list of all requests, including ones which have been responded to.

all_units

.. deprecated:: 0.6.1 Use :attr:all_joined_units instead

endpoint_name

Relation name of this endpoint.

is_joined

Whether this endpoint has remote applications attached to it.

jobs

Return a list of all jobs to be registered.

joined

.. deprecated:: 0.6.3 Use :attr:is_joined instead

def manage_flags(self)

Method that subclasses can override to perform any flag management needed during startup.

This will be called automatically after the framework-managed automatic flags have been updated.

new_jobs

Return a list of new jobs to be registered.

new_requests

A list of requests which have not been responded.

Requests should be handled by the charm and then responded to by calling request.respond(...).

relations

Collection of :class:Relation instances that are established for this :class:Endpoint.

This is a :class:KeyList, so it can be iterated and indexed as a list, or you can look up relations by their ID. For example::

rel0 = endpoint.relations[0]
assert rel0 is endpoint.relations[rel0.relation_id]
assert all(rel is endpoint.relations[rel.relation_id]
           for rel in endpoint.relations)
print(', '.join(endpoint.relations.keys()))