Struct FastPublisherBuilder 

pub struct FastPublisherBuilder { /* private fields */ }

Builder for a FastPublisher.

Obtained via FastPublishExt::fast_publish. Call build to validate configuration and produce a ready-to-use publisher.

All setters are optional; defaults match ADR-50 recommendations:

• flow = 100 (ack every 100 messages ceiling)
• max_outstanding_acks = 2
• gap_mode = Fail
• ack_timeout = <JetStream context default>

Implementations

impl FastPublisherBuilder

pub fn flow(self, flow: u16) -> Self

Set the client-requested maximum flow — the upper bound on how often the server will send flow acks. The server may choose a lower effective flow.

Must be at least 1. Values of 0 are clamped to 1.

pub fn max_outstanding_acks(self, n: u16) -> Self

Set the number of flow-ack-batches that can be in flight before the publisher stalls and waits for an ack. Valid range is 1..=3.

• 1 behaves like synchronous async publish throttled to flow N
• 2 is the ADR-50 recommended default (optimal for most cases)
• 3 is useful on higher-RTT links

Values outside the range are returned as an error from build.

pub fn ack_timeout(self, timeout: Duration) -> Self

Set the timeout for waiting on flow acks and the final commit ack.

When the publisher is stalled waiting for an ack, it will auto-send pings every ack_timeout / 3 to recover from lost acks, giving up after the full ack_timeout elapses.

pub fn gap_mode(self, mode: GapMode) -> Self

Set the gap handling mode. Default: GapMode::Fail.

pub fn on_error<F>(self, handler: F) -> Self

where F: FnMut(FastPublishError) + Send + 'static,

Register a callback invoked for asynchronous events: gap detections, per-message flow errors, and server-side fast-batch errors.

The callback is called on the publisher’s task synchronously from the middle of add / commit / close, so it must be fast and non-blocking.

pub fn build(self) -> Result<FastPublisher, FastPublishError>

Validate configuration and produce a FastPublisher.

The subscription to the batch inbox is NOT created here — it is lazily opened on the first add / commit / close. This matches the Go reference implementation and avoids wasted subscriptions when a publisher is built and then dropped unused.

Errors

• FastPublishErrorKind::InvalidConfig if max_outstanding_acks is outside 1..=3.
• FastPublishErrorKind::InvalidInboxShape if the client’s new_inbox() does not produce a two-token inbox (required by the server’s reply-subject parser).