6.6. Custom functions

You can use the sysout function for logging, as shown in the following example:

{
  "functions": [
    {
      "name": "logInfo",
      "type": "custom",
      "operation": "sysout:INFO"
    }
  ]
}

The string after the : is optional and is used to indicate the log level. The possible values are TRACE, DEBUG, INFO, WARN, and ERROR. If the value is not present, INFO is the default.

In the state definition, you can call the same sysout function as shown in the following example:

{
  "states": [
    {
      "name": "myState",
      "type": "operation",
      "actions": [
        {
          "name": "printAction",
          "functionRef": {
            "refName": "logInfo",
            "arguments": {
              "message": "\"Workflow model is \\(.)\""
            }
          }
        }
      ]
    }
  ]
}

In the previous example, the message argument can be a jq expression or a jq string using interpolation.

OpenShift Serverless Logic supports the java functions within an Apache Maven project, in which you define your workflow service.

The following example shows the declaration of a java function:

{
  "functions": [
    {
      "name": "myFunction", 

      "type": "custom", 

      "operation": "service:java:com.acme.MyInterfaceOrClass::myMethod" 

    }
  ]
}

OpenShift Serverless Logic provides an implementation of a custom function through the knative-serving add-on to invoke Knative services. It allows you to have a static URI, defining a Knative service, that is used to perform HTTP requests. The Knative service defined in the URI is queried in the current Knative cluster and translated to a valid URL.

The following example uses a deployed Knative service:

$ kn service list
NAME                              URL                                                                      LATEST                                  AGE     CONDITIONS   READY   REASON
custom-function-knative-service   http://custom-function-knative-service.default.10.109.169.193.sslip.io   custom-function-knative-service-00001   3h16m   3 OK / 3     True

You can declare a OpenShift Serverless Logic custom function using the Knative service name, as shown in the following example:

  "functions": [
    {
      "name": "greet", 

      "type": "custom", 

      "operation": "knative:services.v1.serving.knative.dev/custom-function-knative-service?path=/plainJsonFunction", 

    }
  ]

OpenShift Serverless Logic offers the REST custom type as a shortcut. When using custom rest, in the function definition, you specify the HTTP URI to be invoked and the HTTP method (get, post, patch, or put) to be used. This is done by using the operation string. When the function is invoked, you pass the request arguments as you do when using an OpenAPI function.

The following example shows the declaration of a rest function:

  {
  "functions": [
    {
      "name": "multiplyAllByAndSum", 

      "type": "custom", 

      "operation": "rest:post:/numbers/{multiplier}/multiplyByAndSum" 

    }
  ]
}

When using the relative endpoints, you must specify the host as a property. The format of the host property is kogito.sw.functions.<function_name>.host. In this example, kogito.sw.functions.multiplyAllByAndSum.host is the host property key. You can override the default port (80) if needed by specifying the kogito.sw.functions.multiplyAllAndSum.port property.

This endpoint expects as body a JSON object whose field numbers is an array of integers, multiplies each item in the array by multiplier and returns the sum of all the multiplied items.