This demo shows how to set up a custom SequencingPolicy.
To that end, a FlightIdSequencingPolicy implementation is present. This SequencingPolicy implementation first
validates whether it handles a FlightEvent implementation. If it does, it returns the FlightId as the sequence
identifier. Through this approach, the FlightIdSequencingPolicy ensures that all events with the same FlightId will
be handled in order within a distributed environment.
The implementation of the FlightIdSequencingPolicy is concise because of the common FlightEvent used by all flight
event implementations. Without this base event, the FlightIdSequencingPolicy would include an if/else or switch
statement containing all flight events to achieve the same.
As a bonus, this sample shows how we can achieve the same result with the PropertySequencingPolicy.
For more information on sequencing policies (like other implementations) check this page.
This sample project is a Spring Boot application, and as such, we can run it as any other Spring Boot application.
It has a simple /test/bulk/{amount} endpoint where you can generate a bulk of events.
These events are directly published on the EventGateway, resulting in the FlightTimeProjector handling them.
The FlightTimeProjector in turn logs the thread identifier and flight identifier for every event it handles.
Through this, the console shows that a single thread will handle all events for a given FlightId in order.
Since Axon Server is a requirement for this sample, a docker-compose file is provided.
Also, if you are on Intellij, a requests.http file is provided to make it easy to call the endpoints.