gistfile1.txt

Idempotent actor API example.

1. Actors go from PENDING -> CREATED -> [RECONSTRUCTING -> CREATED] -> DEAD
2. A single client may issue multiple updates, it is important these updates aren't re-ordered.

This can be handled by making the actor update calls idempotent.

Non-idempotent:
  def AsyncUpdate(actor_id, actor_state)
  
Idempotent:
  def SetActorPendingIfNotExists(actor_id)
  def SetActorCreatedAtVersion(actor_id, actor_lifetime_version)  # version is 0, 1, 2, 3 etc.
  def SetActorDeadAtVersion(actor_id, actor_lifetime_version)  # suppressed if version already past

The GCS server can simply ignore requests that are "overwritten" by more recent versions.