We make following HEADERS under priority control:
* push response HEADERS
* HEADERS submitted by nghttp2_submit_response
Currently, HEADERS submitted by nghttp2_submit_headers is not attached
to stream. This is because it may be used as non-final response
header and application may submit final response using
nghttp2_submit_response without checking non-final response header
transmission.
We simulate resource sharing by decreasing weight. The thing is if
weight is wrapped, that item continues to send DATA until its weight
gets lowered under the other items. This commits fix this issue.
We tried several times about this subject, but for the current
HTTP/2.0 priority scheme, we think it is best to serve the highest
priroty streams first (interleaving streams if there are several
higest ones). There are an issue when aggregating several frontend
connections to one connection in backend, but it is HTTP/2.0
spec issue, rather than implementation.