[nginx] HTTP/2: fixed the "http request count is zero" alert.

[Maxim Dounin]

details:   http://hg.nginx.org/nginx/rev/e2f13011343e
branches:  stable-1.10
changeset: 6755:e2f13011343e
user:      Valentin Bartenev <vbart at nginx.com>
date:      Thu Jun 16 20:55:11 2016 +0300
description:
HTTP/2: fixed the "http request count is zero" alert.

When the stream is terminated the HEADERS frame can still wait in the output
queue.  This frame can't be removed and must be sent to the client anyway,
since HTTP/2 uses stateful compression for headers.  So in order to postpone
closing and freeing memory of such stream the special close stream handler
is set to the write event.  After the HEADERS frame is sent the write event
is called and the stream will be finally closed.

Some events like receiving a RST_STREAM can trigger the read handler of such
stream in closing state and cause unexpected processing that can result in
another attempt to finalize the request.  To prevent it the read handler is
now set to ngx_http_empty_handler.

Thanks to Amazon.

diffstat:

 src/http/v2/ngx_http_v2.c |  1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diffs (11 lines):

diff --git a/src/http/v2/ngx_http_v2.c b/src/http/v2/ngx_http_v2.c
--- a/src/http/v2/ngx_http_v2.c
+++ b/src/http/v2/ngx_http_v2.c
@@ -3935,6 +3935,7 @@ ngx_http_v2_close_stream(ngx_http_v2_str
 
     if (stream->queued) {
         fc->write->handler = ngx_http_v2_close_stream_handler;
+        fc->read->handler = ngx_http_empty_handler;
         return;
     }