Skip to content
Fibril

Core model

Fibril uses a strict queue state machine. Each offset exists in at most one of three states:

Ready -> Inflight -> Acked
  ^         |
  +---------+
   retry or expired lease

Ready

Section titled “Ready”

A ready message is eligible for delivery. Consumers pull work rather than receiving an unbounded push stream.

Inflight

Section titled “Inflight”

Polling leases a message to a consumer until a deadline. If the consumer does not settle the message before expiry, the broker can return it to Ready.

Acked

Section titled “Acked”

Acknowledgement is final. An acked offset does not re-enter delivery.

Explicit settlement

Section titled “Explicit settlement”

Manual-ack consumers decide what happens after processing:

msg.complete().await?; // terminal success
msg.retry().await?;    // requeue immediately
msg.fail().await?;     // terminal failure

retry_after(..) is represented in the client API but is not wired through the full path yet.

Why leasing

Section titled “Why leasing”

Leasing makes failure recovery explicit. A consumer can disappear without permanently taking messages with it, and bounded prefetch gives the broker a concrete backpressure mechanism.