relayConcurrency property
Bounded relay handling (issue #794): at most relayConcurrency relays run at once; overflow queues up to relayQueueLimit deep and answers 503 beyond that — backpressure, not OOM. A request body larger than relayMaxBodyBytes is a 413; the upstream leg gets a relayConnectTimeout and a per-chunk relayIdleTimeout (which also bounds a stalled client body). Defaults are modest.
Implementation
final int relayConcurrency;