Continue-As-New

How to Continue-As-New

Continue-As-New enables a Workflow Execution to close successfully and create a new Workflow Execution in a single atomic operation if the number of Events in the Event History is becoming too large. The Workflow Execution spawned from the use of Continue-As-New has the same Workflow Id, a new Run Id, and a fresh Event History and is passed all the appropriate parameters.

Workflows that need to rerun periodically could naively be implemented as a big while loop with a sleep where the entire logic of the Workflow is inside the body of the while loop. The problem with this approach is that the history for that Workflow will keep growing to a point where it reaches the maximum size enforced by the service.

ContinueAsNew is the low level construct that enables implementing such Workflows without the risk of failures down the road. The operation atomically completes the current execution and starts a new execution of the Workflow with the same Workflow Id. The new execution will not carry over any history from the old execution.

To trigger this behavior, use Workflow::continueAsNew or Workflow::newContinueAsNewStub method:

#[Workflow\WorkflowMethod]
public function periodic(string $name, int $value = 0)
{
    for ($i = 0; $i < 100; $i++) {
        // do something
        $value++;
    }

    // maintain $value counter between runs
    return Workflow::newContinueAsNewStub(self::class)->periodic($name, $value);
}