Query Service

The Query Service, on the other hand, is defined in the queries.service section within the config.yml file. Similar to the Command Service, it must inherit from QueryService.

class TicketQueryService(QueryService):
    @enroute.broker.query("GetTicketQRS")
    @enroute.rest.query(f"/tickets/{{uuid:{UUID_REGEX.pattern}}}", "GET")
    async def get_ticket(self, request: Request) -> Response:
        ...

The actual power of a query service lies in its independent database. Thus, although the command service works as an event sourced platform, the query service can perform queries using any other model, no matter it is a graph, a document oriented model or so.

How does Minos help you craft that database? Minos encourages the use of a Repository that abstracts the creation and access to that model you want to use.

class OrderQueryRepository(MinosSetup):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.engine = create_engine("postgresql+psycopg2://{user}:{password}@{host}:{port}/{database}".format(**kwargs))
        self.session = sessionmaker(bind=self.engine)()

    async def _setup(self) -> None:
        META.create_all(self.engine)

    @classmethod
    def _from_config(cls, *args, config: MinosConfig, **kwargs) -> OrderQueryRepository:
        return cls(*args, **(config.repository._asdict() | {"database": "order_query_db"}) | kwargs)

By extending MinosSetup, Minos handles the creation of the model by extending the _setup() method. Then queries can be performed within it the get data from the data source.

class OrderQueryRepository(MinosSetup):
    async def create(self, **kwargs) -> None:
        kwargs = {k: v if not isinstance(v, FieldDiff) else v.value for k, v in kwargs.items()}

        kwargs["ticket_uuid"] = kwargs["ticket"]
        kwargs["payment_uuid"] = kwargs["payment"]
        kwargs["customer_uuid"] = kwargs["customer"]["uuid"]
        kwargs["payment_detail"] = dict(kwargs["payment_detail"])
        kwargs["shipment_detail"] = dict(kwargs["shipment_detail"])

        kwargs.pop("payment")
        kwargs.pop("ticket")
        kwargs.pop("customer")

        query = ORDER_TABLE.insert().values(**kwargs)
        self.engine.execute(query)

The repository must be connected to the QueryService class so it is