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Workflow Operations

Pausing and Resuming Workflow Execution

Orquesta workflow execution can be paused by running st2 execution pause <execution-id>. An execution must be in a running state in order for pause to be successful. The execution will initially go into a pausing state, and will go into a paused state when no more tasks are in an active state such as running, pausing, or canceling. When a workflow execution is paused, it can be resumed by running st2 execution resume <execution-id>.

The pause and resume operation will cascade down to subworkflows. Orquesta allows for finer control to workflow with multiple branches. If the pause operation is requested from a subworkflow, the pause will not cascade up to the parent workflow and down to other peers. This supports use case where the user wants to pause only a specific branch but let the rest of the workflow continues. This behavior is the same for resuming from a subworkflow.

Canceling Workflow Execution

A workflow execution can be cancelled by running st2 execution cancel <execution-id>. Workflow tasks that are still running will be allowed to run to completion. During cancelation, no new tasks for the workflow will be scheduled. The execution will remain in canceling status until there are no more active tasks.

Re-running Workflow Execution

A workflow execution can be re-run from the beginning. It is exactly like re-running any EWC execution with the command st2 execution re-run <execution-id>. The re-run is a completely separate action execution with a new action execution ID in EWC and a new workflow execution is created for the new action execution.

Re-running Workflow Execution from Task(s)

There are use cases where users want to re-run the workflow execution for certain task(s). Orquesta allows workflow executions to be re-run from any task(s) as long as the workflow execution is in a completed state (succeeded, failed, or canceled). This is different than using a retry in the workflow definition to tell Orquesta to automatically retry a task execution. Retry is considered during workflow design time. Rerun allows a user to respond and manually react to unexpected issues during runtime. This feature allows a user to rerun a workflow from a specific step without starting from the beginning, especially if the workflow is long running or has many steps.

Given the sequential workflow below where task1 succeeded, task2 failed, and task3 has not executed, the workflow execution can be re-run from any task with the command st2 execution re-run <execution-id> --tasks <task_name>. A new action execution is created for the re-run. However, the workflow execution from the original action execution will be reused.

task1 (succeeded) --> task2 (failed) --> task3 (not executed)

If the task to rerun from is a with items task, there is an additional argument passed to the re-run command that controls whether to reset the task (eg: run all of the with items subtasks) or to only re-run failed items. By default, the with items task will be reset. But in certain use cases, users may want to re-run only failed items. In that case, use the command st2 execution re-run <execution-id> --tasks <task_name> --no-reset <task_name>.

Using the sequential workflow as example, if the user passes task2 twice to the --tasks arg such as st2 execution re-run <execution-id> --tasks task2 task2, the re-run command will recognize that task2 is requested twice and deduplicate the request. If the user passes both task1 and task2 to the --tasks arg such as st2 execution re-run <execution-id> --tasks task1 task2 where task2 is already along the path of execution from task1, than the re-run command will ignore the request for task2 to avoid causing multiple branches of task executions. If the user tries to rerun the workflow execution from task3 with the command st2 execution re-run <execution-id> --tasks task3 where task3 has not been executed before, then the re-run command will return an exception.

A more complex example is where there are multiple parallel branches that are joined in a later task. Given the example flowchart below, let’s say task2 and task3 failed and the user wants to rerun the workflow from both tasks.

                    +--> task2 (failed) --+
task1 (succeeded) --|                     |--> task4
                    +--> task3 (failed) --+

To rerun the workflow execution from both task2 and task3, and then join execution again at task4, use the following command st2 execution re-run <execution-id> --tasks task2 task3. Please note the space in between task names.

If the user wants to rerun from task1 instead, then specify only task1 for the rerun and the other tasks will run per the workflow defintion when task1 completes. The command for this case is st2 execution re-run <execution-id> --tasks task1.

If both task2 and task3 are with items tasks

                    +--> task2 [with-items] (failed) --+
task1 (succeeded) --|                                  |--> task4
                    +--> task3 [with-items] (failed) --+

and the user wants to only re-run the failed items in task2 and task3 (eg: they do not want to reset them), use the command st2 execution re-run <execution-id> --tasks task2 task3 --no-reset task2 task3.

However, to reset task2 but not task3, only task3 needs to be passed to the --no-reset flag. The command in that case would be st2 execution re-run <execution-id> --tasks task2 task3 --no-reset task3.

Finally, the user can also rerun the workflow starting at task1, but in that case both task2 and task3 will be reset, regardless of the arguments to the --no-reset flag.