When using variables, rewriting the URI on Nginx does not work

map $id $backend_host {
 default http://primary -host;
 1 http://primary-host;
 2 http://secondary-host;
}

location / {
 set $id 1;
 proxy_pass $backend_host;
}

location /second/ {
 set $id 2;
 proxy_pass $backend_host/;
 rewrite ^/second(.*)$$1 break;
}

location /second/ {
 proxy_pass http://secondary-host/;
 rewrite ^/ second(.*)$$1 break;
)

map $id $backend_host {
 default primary-host;
 1 primary-host;
 2 secondary-host;
}

 location / {
 set $id 1;
 pr oxy_pass http://$backend_host;
}

location /second/ {
 set $id 2;
 proxy_pass http://$backend_host/;
 rewrite ^/second(.*)$$1 break;
}

I have this atlas:

map $id $backend_host {
 default http://primary-host; 
 1 http://primary-host;
 2 http://secondary-host;
}

The following locations:

location / {
 set $id 1;
 proxy_pass $backend_host;
}

location /second/ {
 set $id 2;
 proxy_pass $backend_host/;
 rewrite ^/second(.*)$$1 break;
}

When publishing to http: // nginx-host / second / some / uri, I found that it belongs to the second location clause, and the URI is being rewritten, but then it is being proxied to the primary host instead of the secondary host.

On the other hand, when I Set the second position Time:

location /second/ {
 proxy_pass http://secondary-host/;
 rewrite ^/second(.*)$$1 break ;
)

That is to say, without using variables, it will work normally.

Nothing can be found in the document explaining the document.

Try this

map $id $backend_host {
 default primary-host;< br /> 1 primary-host;
 2 secondary-host;
}

location / {
 set $id 1;
 proxy_pass http:/ /$backend_host;
}

location /second/ {
 set $id 2;
 proxy_pass http://$backend_host/;
 rewrite ^ /second(.*)$$1 break;
}

http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_pass

or even like this:

proxy_pass $request;

In this case, search for the server name
The described server group, if not found, use a to determine the
parser.

Note: I did not test it