id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	uname	nginx_version
2142	keepalive_timeout 0 will break http2	Jeroen		"From the https://nginx.org/en/CHANGES and the latest change `1.19.7`

>    *) Change: connections handling in HTTP/2 has been changed to better
>       match HTTP/1.x; the ""http2_recv_timeout"", ""http2_idle_timeout"", and
>       ""http2_max_requests"" directives have been removed, the
>       ""keepalive_timeout"" and ""keepalive_requests"" directives should be
>       used instead.

If someone is upgrading from earlier versions in this patch release, http2 will break if there is a `0` for `keepalive_timeout`.
Because we had different parameters in the past, this will silently break your system for http2 clients.

I think what happens is that the requesting end will keeps it's stream open, but nginx will terminate it because 0 has passed.

We use `nginx:alpine` docker image, which was automatically updated.

To reproduce using docker, but will work on any environment:

Start nginx with self-signed certificate and `http2` enabled

{{{
docker run --rm -it --name=host --entrypoint=/bin/sh nginx:1.19.7-alpine

apk add --no-cache openssl

cd /etc/nginx
openssl req -keyout cert.key -nodes -out cert.crt -newkey rsa:4096 -days 365 -x509
# ENTER A FEW TIMES

# update keepalive and logging
sed -e 's/keepalive_timeout\s*65;/keepalive_timeout 0;/' -e 's#error_log\s*/var/log/nginx/error.log#error_log stdout#' -e 's#access_log */var/log/nginx/access.log#access_log /dev/stdout#' -i nginx.conf

}}}

`conf.d/default.conf`
{{{
server {
    listen       80;
    listen      443 ssl http2;
    server_name  localhost;

ssl_certificate cert.crt;
ssl_certificate_key cert.key;

... snap


}}}

start nginx without a daemon: `nginx -g'daemon off;'`

In a new console:
{{{
docker run --rm -it --link host alpine

apk add --no-cache curl

curl -vk 'https://host/' -http2 # http2 is the default in latest curl's
# repeat several times, sometimes a succesfull response can be generated
}}}

change the value to something else than `0` and start again.
{{{
sed -e 's/keepalive_timeout\s*0;/keepalive_timeout 65;/' -i nginx.conf

nginx -g'daemon off;'
}}}

If you `curl` again, everything will work just fine.

My suggestion would be to raise an error/warning on start when a zero value is set and `http2` is enabled, `http2` should never accept a zero value for `keepalive_timeout`

"	defect	closed	major	nginx-1.19	nginx-core	1.19.x	fixed	keepalive_timeout			"nginx version: nginx/1.19.7
built by gcc 10.2.1 20201203 (Alpine 10.2.1_pre1) 
built with OpenSSL 1.1.1i  8 Dec 2020 (running with OpenSSL 1.1.1j  16 Feb 2021)
TLS SNI support enabled
configure arguments: --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --modules-path=/usr/lib/nginx/modules --conf-path=/etc/nginx/nginx.conf --error-log-path=/var/log/nginx/error.log --http-log-path=/var/log/nginx/access.log --pid-path=/var/run/nginx.pid --lock-path=/var/run/nginx.lock --http-client-body-temp-path=/var/cache/nginx/client_temp --http-proxy-temp-path=/var/cache/nginx/proxy_temp --http-fastcgi-temp-path=/var/cache/nginx/fastcgi_temp --http-uwsgi-temp-path=/var/cache/nginx/uwsgi_temp --http-scgi-temp-path=/var/cache/nginx/scgi_temp --with-perl_modules_path=/usr/lib/perl5/vendor_perl --user=nginx --group=nginx --with-compat --with-file-aio --with-threads --with-http_addition_module --with-http_auth_request_module --with-http_dav_module --with-http_flv_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_mp4_module --with-http_random_index_module --with-http_realip_module --with-http_secure_link_module --with-http_slice_module --with-http_ssl_module --with-http_stub_status_module --with-http_sub_module --with-http_v2_module --with-mail --with-mail_ssl_module --with-stream --with-stream_realip_module --with-stream_ssl_module --with-stream_ssl_preread_module --with-cc-opt='-Os -fomit-frame-pointer -g' --with-ld-opt=-Wl,--as-needed
"