Previously we scheduled the transmission of response HEADERS using
priority tree in the belief that it allows more better utilization of
bandwidth for prioritized streams. But to reduce the overhead of
reconstruction of priority queue when connection level flow control
window is depleted, we just don't check priority tree in this case.
This means that response HEADERS frames are not sent even though they
are not flow controlled. This could waste bandwidth. To improve this
situation, we stop scheduling response HEADERS with priority tree for
now. Now they are just sent in the order they submitted. The
response body DATA continued to be scheduled with priority tree as
before.
The added API is nghttp2_session_change_stream_priority(). This
provides the same functionality to re-prioritize stream when PRIORITY
frame. is received, but we do it without PRIORITY frame. This could
be useful for server to change pushed stream's priority silently.
HTTP/2 and HPACK are going to be published as RFC, but ALTSVC is still
in draft state. To make our API stable, it would be better to remove
ALTSVC API for 1.0.0 release.
nghttp2_submit_request and nghttp2_submit_response will set
NGHTTP2_FLAG_END_STREAM after all given data is sent (data could be
0). This means we have no way to send trailers. In this commit, we
added NGHTTP2_DATA_FLAG_NO_END_STREAM flag. The application can set
this flag in *data_flags inside nghttp2_data_source_read_callback. If
NGHTTP2_DATA_FLAG_EOF is set, library automatically set
NGHTTP2_FLAG_END_STREAM. But if both NGHTTP2_DATA_FLAG_EOF and
NGHTTP2_DATA_FLAG_NO_END_STREAM are set, NGHTTP2_FLAG_END_STREAM will
not set by library. Then application can use new
nghttp2_submit_trailer() to send trailers. nghttp2_submit_trailer()
will set NGHTTP2_FLAG_END_STREAM and it is actually thing wrapper of
nghttp2_submit_headers().
nghttp2_submit_shutdown_notice() is used to notify the client that
graceful shutdown is started. We expect that after this call, the
server application should send another GOAWAY using
nghttp2_submit_goaway() with appropriate last_stream_id. In this
commit, we also added nghttp2_session_get_last_proc_stream_id(), which
can be used as last_stream_id parameter.
This commit implements graceful shutdown in nghttpx. The integration
test for graceful shutdown is also added.
nghttp2_mem structure is introduced to hold custom memory allocator
functions and user supplied pointer. nghttp2_mem object can be passed
to nghttp2_session_client_new3(), nghttp2_session_server_new3(),
nghttp2_hd_deflate_new2() and nghttp2_hd_inflate_new2() to replace
standard malloc(), free(), calloc() and realloc(). nghttp2_mem
structure has user supplied pointer mem_user_data which can be used as
per session/object memory pool.
This change will utilize last_stream_id in GOAWAY extensively. When
GOAWAY is received with a last_stream_id, library closes all outgoing
streams whose stream_id > received last_stream_id.
nghttp2_on_stream_callback is called for each stream to be closed.
When GOAWAY is sent with a last_stream_id, library closes all incoming
streams whose stream_id > sent last_stream_id.
nghttp2_on_stream_callback is called for each stream to be closed.
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.
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.
Motivation:
The send window size is currently fixed by a macro at compile time.
In order for users of the library to impact the send window size they
would have to change a macro at compile time. The window size may be dynamic
depending on the environment and deployment scheme. The library users
currently have no way to change this parameter.
Modifications:
Add a new optional callback method which is called before data is sent to
obtain the desired send window size. The callback return value will be
subject to a range check for the current session, stream, and settings
limits defined by flow control.
Result:
Library users have control over their send sizes.
Reworked no automatic WINDOW_UPDATE feature. We added new API
nghttp2_session_consume() which tells the library how many bytes are
consumed by the application. Instead of submitting WINDOW_UPDATE by
the application, the library is now responsible to submit
WINDOW_UPDATE based on consumed bytes. This is more reliable method,
since it enables us to properly send WINDOW_UPDATE for stream and
connection individually. The previous implementation of nghttpx had
broken connection window management.
Since we do not call on_data_chunk_recv_callback for ignored DATA
chunk, if nghttp2_option_set_no_auto_connection_window_update is used,
application may not have a chance to send connection WINDOW_UPDATE.
To fix this, we accumulate those received bytes, and if it exceeds
certain number, we automatically send connection-level WINDOW_UPDATE.
Add last_stream_id parameter to nghttp2_submit_goaway(). To terminate
connection immediately with application chosen last stream ID,
nghttp2_session_terminate_session2() was added.
ALTSVC and BLOCKED frames are now extension frames. To add new
extension frame without modifying nghttp2_frame union, which causes so
name bump, we separated extension frames from core frames.
nghttp2_frame includes generic nghttp2_extension. The payload member
of nghttp2_extension will point to the structure of extension frame
payload. The frame types of extension frames are defined in
nghttp2_ext_frame_type.
Previously stream ID was assigned just before HEADERS or PUSH_PROMISE
was serialized and nghttp2_submit_{request, headers, push_promise} did
not return stream ID. The application has to check assigned stream ID
using before_frame_send_callback. Now it is apparent that priority is
meant to DATA transfer only. Also application can reorder the
requests if it wants. Therefore we can assign stream ID in
nghttp2_submit_* functions and return stream ID from them. With this
change, now application does not have to check stream ID using
before_frame_send_callback and its code will be simplified.
nghttp2_submit_{headers,request}: Return NGHTTP2_ERR_INVAILD_ARGUMENT
if pri_spec->type is invalid.
nghttp2_submit_push_promise: Return NGHTTP2_ERR_PROTO if issued by
client.
nghttp2_submit_altsvc: Return NGHTTP2_ERR_PROTO instead of
NGHTTP2_ERR_INVALID_STATE if issued by client.
Tatsuhiro Tsujikawa
Alexis La Goutte
Scott Mitchell