The SSLSubscriptionWrapper is subject to race conditions if demand increased by request() is not exhausted by the time the subscription is switched by setSubscription.

Some synchronization is required to present a consistent view of the subscripton state, so that pending demand can be consistently transferred to the new the subscription.

This mostly affects HTTP/1.1 over TLS since each new exchange will cause the subscription to be switched to the new exchange. The race condition is elusive and hard to reproduce. when it occurs, it mostly causes tests to fail in jtreg timeout as the demand from upstream may not be transferred properly.