This is same issue described in https://github.com/h2o/h2o/issues/268.
That is if SSL object has decrypted data buffered inside it, and
application does not read it for some reason (e.g., rate limit), we
have to check the existence of data using SSL_pending. This is
because buffered data inside SSL is not notified by io watcher. It is
obvious, but we totally missed it.
nghttpx code normally reads everything until SSL_read returns error
(want-read). But if rate limit is involved, we stop reading early.
Also in HTTP/1 code, while processing one request, we just read until
buffer is filled up. In these cases, we may suffer from this problem.
This commit fixes this problem, by performing SSL_pending() and if it
has buffered data and read io watcher is enabled, we feed event using
ev_feed_event().
To avoid buffer copy in nghttp2_data_source_read_callback, this commit
introduces NGHTTP2_DATA_FLAG_NO_COPY and nghttp2_send_data_callback.
By using NGHTTP2_DATA_FLAG_NO_COPY in
nghttp2_data_source_read_callback, application can avoid to copy
application data to given buffer. Instead, application has to
implement nghttp2_send_data_callback to send complete DATA frame by
itself. We see noticeable performance increase in nghttpd and
tiny-nghttpd using this new feature. On the other hand, nghttpx does
not show such difference, probably because buffer copy is not
bottleneck. Using nghttp2_send_data_callback adds complexity, so it
is recommended to measure the performance to see whether this extra
complexity worth it.
It turns out that the cause of complication in backend request line
construction is a absolute-form in HTTP/1 request. In HTTP/2, we have
separated pseudo-header fields and no problem at all. In this commit,
we parse request URI in HTTP/1 frontend and extract values from it to
make backend logic simpler. This patch removes host header field
emission in HTTP/2 backend if :authority is emitted. It also rewrites
host header field with authority part in absolute-form URI as per RFC
7230.
Currently, we use same number of HTTP/2 sessions per worker with given
backend addresses. New option to specify the number of HTTP/2 session
per worker will follow.
Tatsuhiro Tsujikawa
mod-h2-dev