Trait Consumer 

pub trait Consumer: Send + Sync {
    // Required methods
    fn set_threads(&self, n: usize) -> Result<(), ResizeError>;
    fn live_threads(&self) -> usize;
    fn work(&self) -> Work;

    // Provided method
    fn set_measurement_mode(&self, _mode: ProducerMeasurementMode) { ... }
}

The side that consumes decoded bytes: mapping, aligning, counting.

Implementors resize a worker pool and report how much work it has done.

Required Methods

fn set_threads(&self, n: usize) -> Result<(), ResizeError>

Ask for n worker threads. May take effect gradually.

Returning success acknowledges the request, not its completion. The broker observes Self::live_threads before spending the released capacity on the producer.

fn live_threads(&self) -> usize

Workers actually running now, which may lag what was asked for.

Diagnostic only, and deliberately not “the target”: the broker tracks what it asked for itself. The gap between the two is what you want in a log when a split looks wrong, because it separates “the broker decided badly” from “the broker decided well and the pool has not caught up”. Reporting the target here would hide exactly that distinction.

fn work(&self) -> Work

Cumulative work. See Work for the two contracts that matter.

Publish more often than once per batch. A counter updated only at batch boundaries cannot be sampled faster than a batch completes, and a window containing no completed batch reads as zero work — indistinguishable from a totally idle consumer, and reporting maximum starvation for one running flat out. BusyMeter handles this.

Provided Methods

fn set_measurement_mode(&self, _mode: ProducerMeasurementMode)

Switch instrumentation between decision-quality and settled cadence.

Most consumers can leave this as a no-op. Consumers for which publishing progress is itself measurable work may use a finer cadence only while a decision is open and a coarser cadence in steady state.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors