QueueInputStream

A blocking InputStream fed by chunks pushed from a reactive (push-based) source, letting a blocking http4k handler consume a body that the underlying framework delivers asynchronously.

The source calls push/end/fail; the http4k handler (on a worker thread) pulls via read. requestMore is invoked whenever the consumer needs the next chunk, so the source only delivers when asked - that is the backpressure. The blocking read must never run on the same thread that calls push, or it deadlocks.