Nginx error -Starting nginx: nginx: emerg unknown "status" variable - nginx

Question

What I am trying to do using nginx is- to call a backend for authentication and if the response is successful I will redirect to website 1 (for example -google.com) and if authentication fail I will redirect to website2(facebook for example).
Below is my nginx.conf-
user nginx;
worker_processes 1;
error_log /var/log/nginx/error.log;
pid /var/run/nginx.pid;
events {
worker_connections 1024;
}
http {
include /etc/nginx/mime.types;
default_type application/octet-stream;
log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'[===>$status] $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';
access_log /var/log/nginx/access.log main;
sendfile on;
keepalive_timeout 65;
# Load config files from the /etc/nginx/conf.d directory
# The default server is in conf.d/default.conf
include /etc/nginx/conf.d/default.conf;
}
The default.conf file is as below -
server {
listen 80 default_server;
server_name _;
#charset koi8-r;
#access_log logs/host.access.log main;
location / {
# root /usr/share/nginx/html;
# index index.html index.htm;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header Host $host;
proxy_pass http://backend_ip_Address;
set $my_var 0;
if ($status = "200"){
set $my_var 1;
}
#if($status = 4xx) {
# set $my_var 2;
#}
if ($my_var = 1){
proxy_pass http://www.google.com;
}
if ($my_var = 2) {
proxy_pass http://www.facebook.com;
}
}
error_page 404 /404.html;
location = /404.html {
root /usr/share/nginx/html;
}
# redirect server error pages to the static page /50x.html
#
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root /usr/share/nginx/html;
}
}
The issue I am facing is when I am trying to execute sudo service nginx restart with this configuration I am getting below error-
Starting nginx: nginx: [emerg] unknown "status" variable
The same $status is also present in nginx.conf log configuration and it's logging the response code properly like 301, 200 etc. But the same status variable is not working in default.conf file. Any help on what I am doing wrong?
I tried replacing status with body_bytes_sent header and it's works.
By google search https://www.google.co.in/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=nginx++unknown+%22status%22+variable only related information is https://www.drupal.org/node/2738983 but no much help to resolve this.

Answer 1

status variable is defined on very late phase, after request is processed and response is ready to sent back.
You cannot use it for conditional routing.
Usually it's used for logging.
Here you may read about nginx directives execution order and phases:
https://openresty.org/download/agentzh-nginx-tutorials-en.html