Struct FlowController 

pub struct FlowController { /* private fields */ }

Ticket-based write-admission flow controller.

Holds the soft-target policy and the live throttle state. Cheap to share: every field is a single atomic plus the immutable quorum config, so Self::try_admit on the write hot path is a couple of relaxed loads.

Implementations

impl FlowController

pub fn disabled() -> FlowController

A disabled controller (soft target 0): never throttles.

pub fn new(soft_target_lsn: u64, quorum: QuorumConfig) -> FlowController

Build a controller with an explicit soft target and quorum shape.

pub fn configure_soft_target(&self, soft_target_lsn: u64)

Install (or change) the soft target at runtime. 0 disables the feature and immediately releases any active throttle.

pub fn soft_target_lsn(&self) -> u64

Soft target in LSN records. 0 means disabled.

pub fn is_enabled(&self) -> bool

Whether flow control is enabled (soft target > 0).

pub fn is_throttled(&self) -> bool

Whether the throttle is currently engaged.

pub fn observed_lag_lsn(&self) -> u64

Most recent observed max in-quorum replica lag in LSN records.

pub fn observe(&self, replicas: &[ReplicaState], primary_lsn: u64) -> bool

Re-evaluate the throttle from a replica snapshot.

Computes the max lag across in-quorum replicas (async read-replicas excluded) and engages the throttle when it exceeds the soft target, releasing it when the quorum member recovers to/below the target. Returns the resulting throttled state.

pub fn try_admit(&self) -> Admission

Request a write-admission ticket. Granted unless the throttle is engaged. The check is a single relaxed load on the hot path.

Trait Implementations

impl Debug for FlowController

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.