Durable execution, embedded in your service

class PeerToPeerTransfer : Workflow() {
  private val ledger = actions<Ledger>()

  @StateField var isApproved: Boolean? = null

  @WorkflowMethod
  suspend fun transfer(request: TransferRequest): Boolean {
    // Transfers over $1,000 need a human in the loop.
    if (request.amount > 1000) {
      // Hibernate until approved — or up to a day — using zero resources.
      val approved = waitUntil({ isApproved != null }, Duration.ofDays(1))
      if (!approved || isApproved != true) return false
    }
    ledger.debit(request.from, request.amount)
    ledger.credit(request.to, request.amount)
    return true
  }

  // A signal wakes the waiting workflow up from the outside world.
  @SignalMethod
  fun approve(isApproved: Boolean) {
    this.isApproved = isApproved
  }
}

public class PeerToPeerTransfer extends Workflow {
  private final Ledger ledger = actions(Ledger.class);

  @StateField Boolean isApproved;

  @WorkflowMethod(returnType = Boolean.class)
  public CompletableFuture<Boolean> transfer(TransferRequest request) {
    // Transfers over $1,000 need a human in the loop.
    if (request.getAmount() > 1000) {
      // Hibernate until approved — or up to a day — using zero resources.
      boolean approved = waitUntil(() -> isApproved != null, Duration.ofDays(1));
      if (!approved || !isApproved) {
        return CompletableFuture.completedFuture(false);
      }
    }
    ledger.debit(request.getFrom(), request.getAmount());
    ledger.credit(request.getTo(), request.getAmount());
    return CompletableFuture.completedFuture(true);
  }

  // A signal wakes the waiting workflow up from the outside world.
  @SignalMethod
  public void approve(boolean isApproved) {
    this.isApproved = isApproved;
  }
}