Events 1.0 (Deprecated)

Internal events are used within a single project to publish a business occurrence from one domain namespace and trigger an action in another domain namespace.

To do so,

1. create the event in the domain namespace that should publish the event
2. add a payload entity
3. go to the second domain namespace that should receive the event ( see create Domain Namespaces)
4. create an agent
5. select the event you created before from the drop-down

This agent will get triggered whenever an event with this Local Identifier (which will be used as the message key) gets published to the topic specified by the event topic binding. You can later implement what this agent should call, e.g. a domain service, an integration service or you could even call factory commands or instance commands to create new root entities or to update their state and persist them.

One of the most common use cases with events is to publish an event in one microservice and react on it in another microservice. These cross-service events will only work if both microservices have been modelled and implemented with IBM Industry Solutions Workbench. If you want to react on events that are published by external applications or publish an event and react with an external application, please see external events.

In the following example we will use two projects projectA and projectB, where projectA will publish an event and projectB will receive the event (see setting up projects for further details on creating new projects). All used names are just for the example, meaning you are totally free to name your events, namespaces and topics however you want. Just make sure they match between the two projects.

Handling external events is still limited in IBM Industry Solutions Workbench 4.1. You can of course publish events to arbitrary Kafka topics and consume them with any Kafka client you implemented. Therefore, you just need to provide the necessary info regarding the event message to your external application.

Below you can find a sample event message to help you implement your external application to use events published by projects built with IBM Industry Solutions Workbench. This project has

• a domain namespace with the prefix: procs
• an event with the Local Identifier: Testeve
• a payload entity for this event with the Identifier: procs:Testeve_Payload
• a property called title of type String
• a property called message of type String

Event Message Payload Structure:

{
  "type": "procs:Testeve_Payload",
  "id": "e93f0c71-d9a2-4ee6-a22d-fc39fddd8d54",
  "title": "The title",
  "message": "This is the message body"
}

The value for "id" will change on every message. You can use a UUID when sending events.

There will be cases when you want to react on an event that has been published by an external application with a microservice that has been built with IBM Industry Solutions Workbench. Due to the limitations regarding the message key (that is built by concatenating the domain namespace's prefix with the local identifier of the event) it is currently not possible to model agents for arbitrary events.

This message key MUST follow the syntax: prefix:local_identifier and must match the values of the project that should receive the event message.

So if you have the chance to set the message key to the value that the Agent would expect, you can consume external events within IBM Industry Solutions Workbench.

Example:

You want to consume an event with an agent in the domain namespace with the prefix: dom1.

Therefore, you need to model the event inside this domain namespace accordingly to the payload of the event. Let's say you use Event1 as the Local Identifier of that event in Solution Designer. Then, inside the implementation of your external application you would specify the message key to be:

dom1:Event1

With this approach, you are able to consume external events with an Agent.

It is possible to add an entity as payload to the event in case the event should carry data. You can choose between

• Create new private entity
• Select existing entity

To add properties to the payload entity click on the Add capability and choose

• Create new property
• Associate existing property

See domain properties for further details on creating properties.