Event Handler

Introduction

The Genesis low-code platform has a real-time event-driven architecture.

Applications built on the system must respond immediately to different types of input: inputs from users, messages from other systems, market-data updates and internally calculated analytic signals.  These inputs are events.

All the business logic for applications built on the platform is structured around these events. When an event occurs, the business logic immediately fires into action.

As a rough guide, many of the tables you have created need Insert, Modify and Delete events, so that you can specify the processing that these events require.

The vast majority of applications include business workflow.

That could be a simple linear workflow, such as a deal being enriched and approved, or a margin call payment – or it could be a more complex set of steps.

Most applications built on the platform include typical business entities for the financial market, such as orders, trades, bids, allocations and positions. These business entities have a lifecycle where they go through various states. The transition from one state to another is an event that needs to be handled. The paths through those states are workflows, and to assist the workflows, we use state machines.

Event Handlers are conventionally defined in the file app-name-eventhandler.kts.

So, if your application is called positions, then the file would conventionally be named positions-eventhandler.kts.

You can write custom Event Handlers using our APIs. These can be implemented using Kotlin or Java.

note

We recommend using Kotlin to implement Event Handlers.

• Java Event Handlers are implemented using RxJava3 and Sync Event Handlers only. These are described in our page on the Event Handler API
• Async Event Handlers cannot be used, as there is no implementation for Kotlin coroutines in Java.

All events created in the Event Handler are exposed as HTTP/HTTPs REST endpoints automatically by the Genesis platform. You can use any HTTP client, such as postman, to access these custom endpoints.

Open API

important

Open API support was introduced in version 7.0 of the Genesis platform.

To help with external integration and testing, Open API specifications are generated for each resource in the Event Handler.

Internally, the framework uses metadata system to generate JSON schemas for input and return objects in the Open API spec. For more details on this, see our pages on Network messages - type-safe messages and metadata annotations.

Metrics

You can find details of how to use metrics with Event Handlers in our pages on metrics.