This page answers the following questions for Java developers:

• What is Continue-As-New?
• How to Continue-As-New?
• When is it right to Continue-as-New?
• How to test Continue-as-New?

What is Continue-As-New?​

Continue-As-New lets a Workflow Execution close successfully and creates a new Workflow Execution. You can think of it as a checkpoint when your Workflow gets too long or approaches certain scaling limits.

The new Workflow Execution is in the same chain; it keeps the same Workflow Id but gets a new Run Id and a fresh Event History. It also receives your Workflow's usual parameters.

How to Continue-As-New using the Java SDK​

First, design your Workflow parameters so that you can pass in the "current state" when you Continue-As-New into the next Workflow run. This state is typically set to None for the original caller of the Workflow.

class ClusterManagerInput {
  private final Optional<ClusterManagerState> state;
  private final boolean testContinueAsNew;
}

@WorkflowMethod
ClusterManagerResult run(ClusterManagerInput input);

The test hook in the above snippet is covered below.

Inside your Workflow, call the continueAsNew() function with the same type. This stops the Workflow right away and starts a new one.

Workflow.continueAsNew(
  new ClusterManagerInput(Optional.of(state), input.isTestContinueAsNew()));

Considerations for Workflows with Message Handlers​

If you use Updates or Signals, don't call Continue-as-New from the handlers. Instead, wait for your handlers to finish in your main Workflow before you run continueAsNew.

When is it right to Continue-as-New using the Java SDK?​

Use Continue-as-New when your Workflow might hit Event History Limits.

Temporal tracks your Workflow's progress against these limits to let you know when you should Continue-as-New. Call Workflow.getInfo().isContinueAsNewSuggested() to check if it's time.

How to test Continue-as-New using the Java SDK​

Testing Workflows that naturally Continue-as-New may be time-consuming and resource-intensive. Instead, add a test hook to check your Workflow's Continue-as-New behavior faster in automated tests.

For example, when testContinueAsNew == true, this sample creates a test-only variable called maxHistoryLength and sets it to a small value. A helper method in the Workflow checks it each time it considers using Continue-as-New:

private boolean shouldContinueAsNew() {
  if (Workflow.getInfo().isContinueAsNewSuggested()) {
    return true;
  }
  // This is just for ease-of-testing.  In production, we trust temporal to tell us when to
  // continue as new.
  if (maxHistoryLength > 0 && Workflow.getInfo().getHistoryLength() > maxHistoryLength) {
    return true;
  }
  return false;
}