Previously when requests are issued to HTTP/2 downstream connection,
but it turns out that connection is down, handlers of those requests
are deleted. In some situations, we only know connection is down when
we write something to network, so we'd like to handle this kind of
situation in more robust manner. In this change, certain seconds
passed after last network activity, we first issue PING frame to
downstream connection before issuing new HTTP request. If writing
PING frame is failed, it means connection was lost. In this case,
instead of deleting handler, pending requests are migrated to new
HTTP2/ downstream connection, so that it can continue without
affecting upstream connection.
For HTTP/1 backend, -b option can be used several times to specify
multiple backend address. HTTP/2 backend does not support multiple
addresses and only uses first address even if multiple addresses are
specified.
With the combination of HTTP/1 upstream and HTTP/2 downstream,
downstream tells SHRPX_NO_BUFFER while connecting to the backend
server. Previously, we did not call upstream resume_read and upload
was blocked. This commit now calls upstream resume_read to unblock.
This commit also remove pending output buffer size of Http2Session
when calculating downstream connection's buffer is full. This is
desirable since we only operate resume_read by stream basis.
Even after on_stream_close_callback, Http2DownstreamConnection is
still alive and upstream keeps sending response to the client. The
consumed bytes are processed normally (data_source_read_callback) and
also we have a code to consume all allocated bytes for
Http2DownstreamConnection object when it is deleted. This means that
we don't need to and should not consume response data in downstream
on_stream_close_callback. If we do, we may get assertion error in
Http2DownstreamConnection::resume_read().
It is not used by library for a while. It could be used to pass
unsupported extension frames to application, but its interface
requires library to buffer entire frame, which we'd like to avoid.
For unsupported extension frames, we will add new callbacks which does
not require buffering if they are required.
h2-14 now allows extensions to define new error codes. To allow
application callback to access such error codes, we uses uint32_t as
error_code type for structs and function parameters. Previously we
treated unknown error code as INTERNAL_ERROR, but this change removes
this and unknown error code is passed to application callback as is.
Tatsuhiro Tsujikawa