A rejected request answered 200 with the failure only in the body, so every
layer that reads the status line counted it as served: load balancers, metrics,
client-side retry. A load test against this reported the limiter's own
rejections as successful traffic and overstated throughput more than tenfold.
The threshold was a constant in the middleware, which made 200 QPS the ceiling
of every deployment with nothing in the configuration to reveal it. It now
reads extend.rateLimit.inboundQPS; an absent value keeps 200, so an upgrade
changes nothing, and zero disables the limiter for a deployment behind its own
gateway.
Also drops Strategy: system.BBR. Reading sentinel's source, the adaptive
strategy is consulted only for Load and CpuUsage - for InboundQPS the trigger
count is compared directly - so it read as if the limit adapted to the machine
when it never did.
