Integrating with Camel routes

Serverless Workflow can integrate with Apache Camel Routes by adding the Kogito Quarkus Camel Add-on to your project. It enables the workflow engine to identify and call Camel routes declared in YAML or XML in the same workflow project context.

Enabling Quarkus Camel in Serverless Workflow

You can enable Quarkus Camel in your project.

Prerequisites

A workflow application is created.

For more information about creating a workflow, see Creating your first workflow service.

Procedure

To add the Quarkus Camel to your workflow application, add the org.kie.kogito:kogito-addons-quarkus-camel dependency to the pom.xml file of your project as follows:
Dependency to be added to the pom.xml file to enable metrics
<dependency> <groupId>org.kie.kogito</groupId> <artifactId>kogito-addons-quarkus-camel</artifactId> </dependency>

Creating Camel routes in Serverless Workflow

You can add YAML or XML Camel routes to your workflow project.

Procedure

Create a YAML or XML Camel Routes using your IDE or the Kaoto VSCode Editor and place them in the src/main/resources/routes directory.
The route from endpoint must be a direct component. That’s the endpoint producer expected by the workflow engine.
The route response must be in a valid format that the workflow context can understand:
1. A string that contains a valid JSON object
2. A valid Java bean that can be serialized to JSON
3. A Jackson’s JsonNode object
4. Any primitive type (Integer, Float, Decimal, String, etc)

The response will be merged into the workflow state context. If it is an array or a complex object, the response will be added to the special attribute response.

Example of a Camel route with the direct endpoint returning a valid JSON string representation

- from:
    uri: direct:logRouteReplaceHeader (1)
    steps: (2)
      - setBody:
          simple: '{ "id": "${header.WorkflowID}", "arg1": { "arg2": "value1" } }' (3)
      - log:
          message: We received the ${body} (4)

1	Camel route producer definition using the `direct` component
2	Definition of the Camel route steps
3	Replace the Camel message body with a valid JSON object containing the header `WorkflowID` from the workflow context
4	Log the Camel message body in the console for debugging purposes.

Defining and referencing Camel functions in the Workflow DSL

You can define and reference your Camel functions in the workflow definition.

Prerequisites

You have created Camel routes in the workflow Maven project.

Procedure

In the functions definition section of your workflow DSL, declare the Camel route as exemplified below:
Example of a Camel Route function definition
```
{
  "functions": [
    {
      "name": "logRoute",
      "type": "custom",
      "operation": "camel:direct:logRouteReplaceHeader"
    }
  ]
}
```
The operation description must have the prefix camel:direct:, indicating that you want to produce a message to this route via the Camel Direct Component. Direct is the only component supported by Serverless Workflow at the moment.

The operation suffix contains the name of the route endpoint. In the case of this example, logRouteReplaceHeader.

The Camel route defined in the workflow must be available in your project during runtime, otherwise, an IllegalArgumentException will be thrown.

To use the Camel function definition in a workflow action, you can simply reference it as you normally would with any other Serverless Workflow function definitions. For example:

Example of a workflow state action referencing

{
  "states": [
    {
      "name": "sendToLog",
      "type": "operation",
      "actions": [
        {
          "functionRef": {
            "refName": "logRoute", (1)
            "arguments": {
              "body": "${ . }", (2)
              "headers": {
                "WorkflowID": "$WORKFLOW.instanceId" (3)
              }
            }
          }
        }
      ],
      "end": true
    }
  ]
}

1	The function reference name, as defined in the function attribute.
2	The body definition. A `jq` expression to be evaluated in runtime resulting in the body payload.
3	The `headers` definition that must be a key/value pair or a valid `jq` expression evaluated in runtime.

Once a message is received back from the Camel route, the data is merged into the workflow payload:

Message payload example returned by the Camel route

{ "id": "777adb97-d297-45fd-9969-efafe4dfb3e7", "arg1": { "arg2": "value1" } }

Example project

There is an example project available on GitHub using this new feature. You can use it as a reference to have a better understanding of the Camel integration with Serverless Workflow.

Additional resources

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