id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	uname	nginx_version
1997	"Error nginx: [emerg] unknown ""upstream_first_byte_time"" variable"	opiumfor@…		"Hello!

I've added the $upstream_first_byte_time to my log format in nginx.conf like this:

log_format json escape=json 
...here goes some other fields...
'""upstream_first_byte_time"": ""$upstream_first_byte_time"", '
...here goes some other fields...
;

But unfortunately the output of ""nginx -V && nginx -T"" is:

nginx version: nginx/1.19.0
built by gcc 9.2.0 (Alpine 9.2.0) 
built with OpenSSL 1.1.1d  10 Sep 2019 (running with OpenSSL 1.1.1g  21 Apr 2020)
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' --with-ld-opt=-Wl,--as-needed

2020/06/05 13:49:21 [emerg] 1#1: unknown ""upstream_first_byte_time"" variable
nginx: [emerg] unknown ""upstream_first_byte_time"" variable
nginx: configuration file /etc/nginx/nginx.conf test failed

What I am doing wrong?

"	defect	closed	major		nginx-module	1.19.x	invalid	ngx_stream_upstream_module		Linux 03870119ec4e 5.4.0-33-generic #37-Ubuntu SMP Thu May 21 12:53:59 UTC 2020 x86_64 Linux	"nginx version: nginx/1.19.0
built by gcc 9.2.0 (Alpine 9.2.0) 
built with OpenSSL 1.1.1d  10 Sep 2019 (running with OpenSSL 1.1.1g  21 Apr 2020)
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' --with-ld-opt=-Wl,--as-needed"