Do While

The Do While task sequentially executes a list of tasks as long as a condition is true. The list of tasks is executed first before the condition is checked, even for the first iteration, just like a regular do .. while task in programming languages.

Definitions

    {
      "name": "do_while_task",
      "taskReferenceName": "do_while_task_ref",
      "type": "DO_WHILE",
      "loopCondition": "", // Condition
      "loopConditionType": "value-param",
      "loopOver": [
        // List of tasks to be executed in the loop
      ]
    }

• When scheduled, each task of this loop will see its taskReferenceName concatenated with __i, with i being the iteration number, starting at 1. Warning: taskReferenceName containing arithmetic operators must not be used.
• Each time the task is performed, the output is saved and indexed by the iteration value. This makes it possible for the condition to check the output of a specific task iteration. (E.g., $.taskReferenceName['iteration]['first_task']).
• The DO_WHILE task is set to FAILED as soon as one of the loopTask fails. In such cases, for the retry, the iteration starts from 1.

Input Parameters

Attributes	Description
loopCondition	Indicates the condition to be evaluated after every iteration. Supported types are value-param, and ECMASCRIPT. If an exception occurs during evaluation, the task is set to FAILED_WITH_TERMINAL_ERROR.
loopOver	Includes the list of tasks to be executed as long as the condition is evaluated to true.

Output Parameters

Attributes	Description
iteration	Indicates the iteration number, which is the current one while executing, and the final one once the loop is finished.
i	Iteration number as a string mapped to the task references names and their output.
*	Any state can be stored here if the loopCondition does so. For example, storage will exist if loopCondition is if ($.LoopTask['iteration'] <= 10) {$.LoopTask.storage = 3; true } else {false}.
keepLastN (No of iterations to keep)	Specify the number of required iterations. On enabling this option, this value is set to 2 by default. You can also choose the option “No limits” based on your preference.

note

• Domain or isolation group execution is unsupported.
• Nested DO_WHILE is unsupported. However, we can achieve a similar functionality as the DO_WHILE task supports SUB_WORKFLOW as a loopOver task.
• Since loopOver tasks will be executed in a loop inside the scope of a parent, the do-while task may not work as expected if it includes branching that crosses outside the DO_WHILE task.
• Branching inside the loopOver task is supported.

Examples

UI

1. Add task type Do While.
2. Select the loop condition type.
3. Add the condition.
4. Add the list of tasks in the loop.

JSON Example

    {
      "name": "do_while_example",
      "taskReferenceName": "do_while_example_ref_1",
      "inputParameters": {},
      "type": "DO_WHILE",
      "loopCondition": "(function () {\n  if ($.do_while_example_ref_1['iteration'] < 3) {\n    return true;\n  }\n  return false;\n})();",
      "loopOver": [
        {
          "name": "sample_loop_task",
          "taskReferenceName": "sample_loop_task",
          "inputParameters": {
            "http_request": {
              "uri": "https://orkes-api-tester.orkesconductor.com/api",
              "method": "GET",
              "connectionTimeOut": 3000,
              "readTimeOut": "3000",
              "accept": "application/json",
              "contentType": "application/json"
            }
          },
          "type": "HTTP"
        }
      ],
      "evaluatorType": "graaljs"
    }

Sample Workflow

{
    "name": "Loop Task",
    "taskReferenceName": "LoopTask",
    "type": "DO_WHILE",
    "inputParameters": {
        "value": "${workflow.input.value}"
    },
    "loopCondition": "if ( ($.LoopTask['iteration'] < $.value ) || ( $.first_task['response']['body'] > 10)) { false; } else { true; }",
    "loopOver": [
        {
            "name": "first task",
            "taskReferenceName": "first_task",
            "inputParameters": {
                "http_request": {
                    "uri": "http://localhost:8082",
                    "method": "POST"
                }
            },
            "type": "HTTP"
        },
        {
            "name": "second task",
            "taskReferenceName": "second_task",
            "inputParameters": {
                "http_request": {
                    "uri": "http://localhost:8082",
                    "method": "POST"
                }
            },
            "type": "HTTP"
        }
    ]
}

The above definition will produce the following execution, assuming three executions occurred (alongside first_task__1, first_task__2, first_task__3, second_task__1, second_task__2, and second_task__3):

{
    "taskType": "DO_WHILE",
    "outputData": {
        "iteration": 3,
        "1": {
            "first_task": {
                "response": {},
                "headers": {
                    "Content-Type": "application/json"
                }
            },
            "second_task": {
                "response": {},
                "headers": {
                    "Content-Type": "application/json"
                }
            }
        },
        "2": {
            "first_task": {
                "response": {},
                "headers": {
                    "Content-Type": "application/json"
                }
            },
            "second_task": {
                "response": {},
                "headers": {
                    "Content-Type": "application/json"
                }
            }
        },
        "3": {
            "first_task": {
                "response": {},
                "headers": {
                    "Content-Type": "application/json"
                }
            },
            "second_task": {
                "response": {},
                "headers": {
                    "Content-Type": "application/json"
                }
            }
        }
    }
}

Using Iteration Key

Sometimes, you may want to use the iteration value/counter in the tasks used in the loop. In this example, an API call is made to GitHub (to the Netflix Conductor repository), but each loop increases the pagination.

{
    "name": "get_all_stars",
    "taskReferenceName": "get_all_stars_loop_ref",
    "inputParameters": {
    "stargazers": "4000"
    },
    "type": "DO_WHILE",
    "loopCondition": "if ($.get_all_stars_loop_ref['iteration'] < Math.ceil($.stargazers/100)) { true; } else { false; }",
    "loopOver": [
        {
            "name": "100_stargazers",
            "taskReferenceName": "hundred_stargazers_ref",
            "inputParameters": {
                "counter": "${get_all_stars_loop_ref.output.iteration}",
                "http_request": {
                    "uri": "https://api.github.com/repos/ntflix/conductor/stargazers?page=${get_all_stars_loop_ref.output.iteration}&per_page=100",
                    "method": "GET",
                    "headers": {
                        "Authorization": "token ${workflow.input.gh_token}",
                        "Accept": "application/vnd.github.v3.star+json"
                    }
                }
            },
            "type": "HTTP",
        }
    ]
}

• The Loop taskReferenceName is "get_all_stars_loop_ref".
• In the loopCondition, the term $.get_all_stars_loop_ref['iteration'] is used.
• In tasks embedded in the loop, ${get_all_stars_loop_ref.output.iteration} is used. In this case, it defines which page of results the API should return.