[−][src]Module dendrite::axon_utils

Axon Utilities

Module axon_utils exports items that can be used to create a complete Event Sourced CQRS application that uses AxonServer as an event store. The whole back-end can be packaged as a single application, but when growing load or complexity demands it, aspects can be taken out and converted to microservices that can be scaled horizontally.

The basic parts of a dendrite application are:

Command API — accepts commands on a gRPC API and forwards them (again over gRPC to AxonServer)
Command worker — subscribes to commands, verifies them against the command projection and sends emitted events to AxonServer
Event processor — subscribes to events and builds a query model from them (there are likely to be multiple query models for a single application)
Query API — accepts queries on a gRPC API and forwards them (again over gRPC to AxonServer)
Query processor — subscribes to queries, executes them against a query model and pass back the results

Structs

AggregateDefinition	The complete definition of an aggregate.
AxonConnection	A connection to AxonServer.
AxonServerHandle	A handle for AxonServer.
EmitApplicableEventsAndResponse	Struct that can be returned by a command handler to supply both the events that have to be emitted and the response to the caller.
QueryResult	Carries the result of a query from handler to processor.
TheAggregateRegistry	Concrete struct that implements `AggregateRegistry`.
TheHandlerRegistry	Concrete struct that implements the `HandlerRegistry` trait.

Traits

AggregateRegistry	Trait that needs to be implemented by the aggregate registry.
ApplicableTo	Describes a `Message` that is applicable to a particular projection type.
AsyncApplicableTo	Describes a `Message` that is asynchronously applicable to a particular projection type.
CommandSink	Trait that is implemented by an object that can be used to send commands to AxonServer.
HandlerRegistry	Describes a registry for handlers for a particular type projection (or context) and a particular return type.
QueryContext	Marker trait that describes the context for a query handler.
QuerySink	Trait that is implemented by an object that can be used to send queries to AxonServer.
TokenStore	Describes a token store.
VecU8Message	Describes a message that can be serialized to a mutable `Vec<u8>`.

Functions

axon_serialize	Converts a `prost::Message` to an Axon `SerializedObject`.
command_worker	Subscribes to commands, verifies them against the command projection and sends emitted events to AxonServer.
create_aggregate_definition	Creates a new aggregate definition as needed by function `command_worker`.
emit	Adds an event that can be applied to the command projection to be emitted to the result of a command handler.
emit_events	Creates a struct that can be returned by a command handler to supply the events that have to be emitted.
emit_events_and_response	Creates a struct that can be returned by a command handler to supply both the events that have to be emitted and the response to the caller.
empty_aggregate_registry	Creates an empty aggregate registry that can be populated with `AggregateHandle`s (most likely: `AggregateDefinition`s).
empty_handler_registry	Creates an empty handler registry for a type of projection and a type of return values that can be populated with SubscriptionHandles.
event_processor	Subscribes to events and builds a query model from them.
init_command_sender	Polls AxonServer until it is available and ready.
query_events	Fetch all events for a given aggregate.
query_processor	Subscribes to queries, executes them against a query model and pass back the results.
wait_for_server	Polls AxonServer until it is available and ready.