Module concurrency 

Available on crate feature cloud only.

Adaptive in-flight concurrency controller for cloud IO (Input only).

Admission control for concurrency uses two budgets:

• A (primary) bytes-based budget to model the bandwidth-delay product (BDP)
• A (secondary) count-based budget to limit the number of in-flight requests

Two models set the bytes-based budget (POLARS_INFLIGHT_BYTE_BUDGET_MODEL):

• Knee (default, knee.rs): measures the smallest budget at which the delivered bandwidth stops growing with the budget.
• TTFB: models the BDP as BW_max * TTFB_est, with Model (records IO observations and models the network: BW_max, TTFB_est, BDP) and Regime (state machine: Init / RampUp / Stable / ProbeUp).

Admission enforces the byte-based and request-based budgets.

Structs

ConcurrencyController

ControllerConfig

HeadRttChannel

Windowed round-trip time of 0-byte metadata (HEAD) requests. Diagnostic only, not to be used for BDP estimation.

HeadRttWindow

One control tick’s worth of HeadRttChannel observations.

InFlightBudget

InFlightPermit

InFlightStats

IoSample

Model

Regime

Enums

RegimeState

Functions

get_inflight_floor_request_budget

Minimum number of requests concurrently in flight, if demand is there.

get_inflight_request_budget

Maximum number of requests concurrently in flight.