ChildJob Looping in Workflow Design

Using ChildJob Looping

In workflow design, there may be some scenarios where it is best to use a childJobLoop instead of the forEach task. Using childJobLoop simplifies the readability of workflows and promotes modularity without having to maintain looping logic in multiple places throughout the workflow. It is also a better way of doing loops (sequential and parallel) through a childJob task.

Task Conversion Process

The main components to converting a forEach task to a childLoop task include:

• The conversion of the looped task to a job of its own.
• The handler task that iterates over an array.
• The input and output variables of the childJob.

Here are the steps:

1. Create a new workflow for the looped tasks in the forEach task.

2. Replace the forEach task in the original worklow with the childJob task and set the Workflow to the child workflow created in the previous step.

3. Set the loopType to sequential or parallel.

4. Set the loopArray to the referenced dataArray. Ensure the items in the loopArray are objects.

All the workflow details involved in the task conversion process are illustrated in the examples below.

Pass Inputs Directly to a Child Job (Basic Example)

Parent Workflow

In the starting workflow (Figure 1), the forEach task is iterating over an array [1,2,3]. For each iteration, the task is making a REST call to an API endpoint.

Figure 1

Create the Child Workflow

Next, create a child workflow for the task that is being looped (Figure 2). As a suggestion, it is easier to clone the original workflow and leave only the looping tasks.

Figure 2

Replace forEach with childJob

Go back to the parent workflow and remove the forEach task. Replace it with childJob.

Figure 3

Set the Loop Type

Open the task details for the childJob task and update the Workflow, Loop Type and Loop Array property fields with the corresponding values. Use Sequential for the Loop Type. Click Save to retain your changes.

Figure 4

Convert Array to Object

For the array passed to the childJob task, the values need to be objects. Go back to the parent workflow and open the “New Job Variable”. Change the data_array input to [{},{},{}] (Figure 5). Click Save to retain your changes.

Figure 5

Run Workflow

Once the “New Job Variable” is updated, click the Run button (▶) to execute the workflow and successfully complete the conversion activity.

Use Transformations to Pass Inputs to a Child Job (Advanced Example)

To build on the basic example presented above, let's explore an alternate mechanism which might be useful in some scenarios.

Restore Parent Workflow

Open the “New Job Variable” and change the data_array input to to “[1,2,3]”. Click Save to restore the parent workflow back to its original state.

Next, to minimize some of the complexity of manually converting the input array, you can use a JST to map how the Loop Array passes input values to the childjob.

Create a JST

Open the task details for the childJob task. Click the plus (+) icon next to the Transformation field to create a JST that can map the Loop Array to input values for the childjob workflow.

Figure 6

Set the Outgoing Schema

On the JST page, set the outgoing schema with an id of num and type of 'integer'. This allows you to pass in the data_array variable to the outgoing schema using the original [1,2,3] input array from the parent workflow. Save and close the JST.

Figure 7

Input for the childJob Task

Next, open task details for the viewData task. For the message variable, change the Reference task to job and the Reference variable to message as shown in Figure 8. Click Save to update the viewData task.

Figure 8

Use the JST configured earlier to pass the $id of message rather than num. This creates the data_array object [{"message":1},{"message":2},{"message":3} that is passed to the childJob task.

Figure 9

Save the transformation and then go back to the parent workflow and click the Run button (▶). Once you “work” the childjob, you will see the Rest Call Output as shown Figure 10.

Figure 10

Output for the childJob Task

Lastly, if the parent workflow requires the output of the childJob task, then use the output data from job_details. In this case, add the viewData task and use it to pass in the job_details.

Figure 11

Next, pass in the job_details output to the body variable.

Figure 12

Run the parent workflow and "work" each childjob viewData task. As shown in Figure 13, the job_details of the childJob task will look something like this in the output.

Figure 13

Each of the loop items will contain the job variables for the job that was completed; however, you will notice no job variables are available. To get the output of the REST API call, go back to the child job in designer mode, choose the RestCall task, and then select (check) the Job Variables box under Outgoing.

Figure 14

Once you run the parent workflow, you will then get the output in job_details for the childJob task for each iteration (Figure 15).

Figure 15

Related Resources

• Itential Video: How to Loop Child Jobs in IAP Workflows