Actor Framework¶

Astra’s actor model is the main concurrency pattern: each actor runs with a mailbox and handles messages without shared mutable state between actors. That keeps reasoning local and scales to many agents.

Model¶

• Message — typed payload from a sender to a target actor.
• Actor — identity, a handler for incoming messages, and a defined shutdown path.
• Runtime — starts actors, delivers messages, and applies backpressure when mailboxes are full (senders must handle “mailbox full” rather than blocking forever).

Lifecycle¶

stateDiagram-v2
  [*] --> created: Spawn
  created --> running: Start
  running --> running: Handle messages
  running --> stopped: Stop
  running --> failed: Error
  failed --> running: Restart policy
  failed --> stopped: Escalate
  stopped --> [*]

Communication¶

Supervision¶

Supervisors manage child actors with policies such as immediate restart, backoff, escalate to parent, or terminate. If a child fails too often in a window, the supervisor stops restart storms by escalating or stopping — same idea as Erlang/OTP supervision trees.

Durable state¶

Actors that own durable state periodically persist snapshots so restarts can resume. Frequency and retention are tuning concerns; see PRD for the intended durability model.