Crate multistore_metering 

Usage metering and quota enforcement middleware.

This crate provides trait abstractions for tracking API usage and enforcing quotas, along with a MeteringMiddleware that wires them into the proxy’s middleware chain. Integrators bring their own storage backends by implementing UsageRecorder and QuotaChecker.

Quick start

use multistore_metering::{MeteringMiddleware, UsageRecorder, QuotaChecker};

// Implement UsageRecorder and QuotaChecker for your storage backend,
// then register the middleware on the ProxyGateway builder:
let metering = MeteringMiddleware::new(my_quota_checker, my_usage_recorder);
gateway_builder.add_middleware(metering);

Architecture

• Pre-dispatch: QuotaChecker::check_quota runs before the request proceeds, using Content-Length as a byte estimate. Return Err(QuotaExceeded) to reject with HTTP 429.
• Post-dispatch: UsageRecorder::record_operation runs after the response is available, recording actual status and byte counts from the backend response.

Structs

MeteringMiddleware

Middleware that enforces quotas pre-dispatch and records usage post-dispatch.

NoopQuotaChecker

A QuotaChecker that always allows requests. Useful when only usage recording is needed, or for testing.

NoopRecorder

A UsageRecorder that does nothing. Useful when only quota checking is needed, or for testing.

QuotaExceeded

Quota violation error returned by QuotaChecker::check_quota.

UsageEvent

A completed operation’s metadata, passed to UsageRecorder::record_operation.

Traits

QuotaChecker

Pre-dispatch quota enforcement.

UsageRecorder

Records completed operations for usage tracking.