# Dendrite

A [Rust](https://www.rust-lang.org) library to connect to [AxonServer](https://axoniq.io/product-overview/axon-server).

See the GitHub project [rustigaan/archetype-rust-axon](https://github.com/rustigaan/archetype-rust-axon) for an example of how to use this code.

## Core concepts

* [Command / Query Responsibility Segregation](http://codebetter.com/gregyoung/2010/02/16/cqrs-task-based-uis-event-sourcing-agh/) (CQRS)
* [Event Sourcing](https://axoniq.io/resources/event-sourcing)
* [Futures and async/await](https://rust-lang.github.io/async-book)
* [gRPC](https://grpc.io/)

## More information

* [dendrite on crates.io](https://crates.io/crates/dendrite)
* [dendrite on docs.rs](https://docs.rs/dendrite)
* [dendrite on GitHub](https://github.com/rustigaan/dendrite)

The crate [dendrite-macros](/dendrite-macros/README.md) provides macros that makes working with the dendrite crate more ergonomic.

This project is a sibling of [dendrite2go](https://github.com/dendrite2go/dendrite) and [archetype-go-axon](https://github.com/dendrite2go/archetype-go-axon), but for the Rust programming language.

## Status

This project has now reached the level of Minimal Viable Deliverable in the sense that the first phase is completed: the current application communicates with AxonServer properly.
Like [archetype-go-axon](https://github.com/dendrite2go/archetype-go-axon) it can do the following:
1. ☑ Set up a session with AxonServer
   * ☑ Enable React app to call a RPC endpoint on the example-command-api service through grpc-web
2. ☑ Issue commands
3. ☑ Register a command handler and handle commands
4. ☑ Submit events
   * ☑ Stream events to UI
5. ☑ Retrieve the events for an aggregate and build a projection
   * ☑ Validate commands against the projection
6. ☑ Register a tracking event processor and handle events
7. ☑ Store records in a query model: Elastic Search
   * ☑ Store tracking token in Elastic Search
8. ☑ Register a query handler and handle queries
   * ☑ Show query results in UI

As well as:

* In-memory caching of aggregate projections
* Access to Axon Command-, Event-, QueryRequest-message in body of handlers.

Now it would be nice to:

* Add support for storing snapshots of aggregate projections in AxonServer.
* Add support for segmentation to distribute the load on tracking event processors.
* Add support for sagas.
* ...