charms.reactive.patterns¶

`BaseRequest`	Base class for requests using the request / response pattern.
`BaseResponse`	Base class for responses using the request / response pattern.
`Field`	Defines a Field property for a Request or Response object.
`FieldFinders`	Metaclass for defining `response_by_FIELD` methods on `RequesterEndpoint` classes.
`FieldHolderDictProxy`	Base class for field holders that makes it act like a dict for easy serialization.
`RequesterEndpoint`	Base class for Endpoints that create requests in the request / response pattern.
`ResponderEndpoint`	Base class for Endpoints that respond to requests in the request / response pattern.
`SetNameBackport`	Metaclass to backport the __set_name__ behavior for data descriptors, which was added in Python 3.6, to earlier versions.

Reference

class charms.reactive.patterns.request_response.BaseRequest(source, request_id)¶

Bases: charms.reactive.patterns.request_response.FieldHolderDictProxy

Base class for requests using the request / response pattern.

Subclasses must set the RESPONSE_CLASS attribute to a subclass of the BaseResponse which defines the fields that the response will use. They must also define additional attributes as :class:`Field`s.

For example:

class TLSResponse(BaseResponse):
    key = Field('Private key for the cert')
    cert = Field('Public cert info')


class TLSRequest(BaseRequest):
    RESPONSE_CLASS = TLSResponse

    common_name = Field('Common Name (CN) for the cert to be created')
    sans = Field('List of Subject Alternative Names (SANs)')

RESPONSE_CLASS = None¶

classmethod create(relation, **fields)¶

Create a new request.

Fields and their values can be passed in to pre-populate the request as keyword arguments, or can be set individually on the resulting request.

classmethod create_or_update(match_fields, relation, **fields)¶

Find a request and update it, or create a new one.

If multiple requests match, only the first one is updated.

Parameters:	match_fields – List of the field names to match by. relation – Relation to find or create the request on. **fields – Name / value pairs to match by and update to.
Returns:	The new or updated request.

Example:

for relation in self.relations:
    JobRequest.create_or_update(match_fields=['job_name'],
                                relation=relation,
                                job_name='foo',
                                job_data=job_data)

create_response(**fields)¶

Create a response to this request.

Fields and their values can be passed in to pre-populate the response as keyword arguments, or can be set individually on the resulting response.

Returns the response object (which can also be accessed as request.response).

egress_subnets¶: Subnets over which network traffic to the requester will flow.

classmethod find(relation=None, **fields)¶

Find the first request whose fields match the given values.

Parameters:	relation – If given, look for the request on a specific relation. **fields – Name / value pairs to match by.

classmethod find_all(**fields)¶

Find all requests whose fields match the given values.

Parameters:	**fields – Name / value pairs to match by.

classmethod get(request_id)¶: Get a specific request by ID.

classmethod get_all()¶: Get a list of all requests (in order of their ID).

ingress_address¶: Address to use if a connection to the requester is required.

is_created¶: Whether this request was created by this side of the relation.

is_received¶: Whether this request was received by the other side of the relation.

request_id¶: UUID for this request. Will be automatically generated.

respond(**fields)¶

Respond to this request. (Alias of create_response().)

Fields and their values can be passed in to pre-populate the response as keyword arguments, or can be set individually on the resulting response.

Returns the response object (which can also be accessed as request.response).

class charms.reactive.patterns.request_response.BaseResponse(request)¶

Bases: charms.reactive.patterns.request_response.FieldHolderDictProxy

Base class for responses using the request / response pattern.

classmethod create(request, **fields)¶

Create a response to the given request.

Fields and their values can be passed in to pre-populate the response as keyword arguments, or can be set individually on the resulting response.

is_received¶

class charms.reactive.patterns.request_response.Field(description)¶

Bases: property

Defines a Field property for a Request or Response object.

Can be set or retrieved like a normal attribute, and will be automatically serialized over the relation using JSON.

class charms.reactive.patterns.request_response.FieldFinders(name, bases, namespace)¶

Bases: type

Metaclass for defining response_by_FIELD methods on RequesterEndpoint classes.

This is done as a metaclass to handle fields on derived classes but to still allow the methods to show up in the class’s documentation.

class charms.reactive.patterns.request_response.FieldHolderDictProxy¶

Bases: dict

Base class for field holders that makes it act like a dict for easy serialization.

class charms.reactive.patterns.request_response.RequesterEndpoint(*args, **kwargs)¶

Bases: charms.reactive.endpoints.Endpoint

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

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

Will automatically manage the following flags:

endpoint.{endpoint_name}.has_responses Set if any responses are available

endpoint.{endpoint_name}.all_responses Set if all requests have responses.

REQUEST_CLASS = None¶

requests¶: A list of all requests which have been submitted.

response_by_field(relation=None, **fields)¶

Find a response by the value(s) of fields on its request.

Parameters:	relation – If given, limit the search to that relation. **fields – Name / value pairs to match by.

responses¶: A list of all responses which have been received.

class charms.reactive.patterns.request_response.ResponderEndpoint(*args, **kwargs)¶

Bases: charms.reactive.endpoints.Endpoint

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

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

Will automatically manage the following flags:

endpoint.{endpoint_name}.has_requests Set if any requests are available

endpoint.{endpoint_name}.new_requests Set if any unhandled requests are available.

REQUEST_CLASS = None¶

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

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(...).

class charms.reactive.patterns.request_response.SetNameBackport¶

Bases: type

Metaclass to backport the __set_name__ behavior for data descriptors, which was added in Python 3.6, to earlier versions.