ngx.location.capture uses wrong certificate from a different server block

Hi,

I am using Nginx 1.19.5 with ngx_http_lua_module. We have been using ngx.location.capture().

Recently we use more server blocks. From the documentation, we expect subrequest is limited to the same server block. But what we have found is that when the set up is like below, the subrequest will randonly use a certificate from the other server block to fire a subrequest.

server {
  listen 11123 ssl;
  ..
  location /main {
    access_by_lua_block {
      ngx.location.capture("/sub")
    }
    proxy_pass https://www.testing.com;
  }
  location /sub {
    proxy_ssl_certificate crt-1.pem;
    proxy_ssl_certificate_key key-1.key;
    proxy_pass https://www.some-domain.com;
  }
} 

server {
  listen 11124 ssl;
  ..
  location /main {
     access_by_lua_block {
      ngx.location.capture("/sub")
    }
    proxy_pass https://www.testing.com;
  }
  location /sub {
    proxy_ssl_certificate crt-2.pem;
    proxy_ssl_certificate_key key-2.key;
    proxy_pass https://www.some-domain.com;
  }
} 

From the above setup. If the main request is using port 11123, the subrequest will sometimes use crt-2.pem instead of crt-1.pem, causing some issues.

Is this an expected behavior? is there any way to fix the issue? Any suggestions welcomed. Thank you!

Start with the ngx.location.capture entry point and reproduce the configuration using the two server blocks on ports 11123 and 11124. Compare which proxy_ssl_certificate is selected for each subrequest and review the module's handling of server context. Done means the subrequest consistently uses the certificate from the originating server block, with the behavior verified for both ports.