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

• AggregateContext
• AggregateDefinition
  The complete definition of an aggregate.
• 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.
• HandleBuilder
• QueryResult
  Carries the result of a query from handler to processor.
• SerializedObject
  Describes a serialized object
• SubmitCommand
• TheAggregateRegistry
  Concrete struct that implements AggregateRegistry.
• TheHandlerRegistry
  Concrete struct that implements the HandlerRegistry trait.
• WorkerControl
• WorkerHandle

Enums

• WorkerCommand

Traits

• AggregateContextTrait
• 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.
• AxonServerHandleAsyncTrait
• AxonServerHandleTrait
• 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. I tried to make it possible to pass an async fn directly to parameter handler, but the return type after desugaring is unnameable (https://internals.rust-lang.org/t/naming-the-return-type-of-an-async-function/10085). So it has to be wrapped in a closure that Box::pins the return value, like this:
• IntoPinFuture
• 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 AggregateHandles (most likely: AggregateDefinitions).
• 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.
• platform_worker
  Subscribes to commands, verifies them against the command projection and sends emitted events to AxonServer.
• platform_worker_for
• 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.

Type Aliases

• WorkerThread