I need to pass an Nginx variable to my PHP 7.0 backend using the excellent library https://github.com/openresty/lua-nginx-module
I prefer to use content_by_lua_block
instead of set_by_lua_block
, because the documentation for the 'set' function states "This directive is designed to execute short, fast running code blocks as the Nginx event loop is blocked during code execution. Time consuming code sequences should therefore be avoided.".
https://github.com/openresty/lua-nginx-module#set_by_lua
However, since the 'content_...' function is non-blocking, the following code does not return in time, and $hello is unset when passed to PHP:
location ~ \.php{
set $hello '';
content_by_lua_block {
ngx.var.hello = "hello there.";
}
fastcgi_param HELLO $hello;
include fastcgi_params;
...
fastcgi_pass unix:/run/php/php7.0-fpm.sock;
}
The problem is, my Lua code has the potential to be "time consuming code sequences" if certain code paths are taken, using crypto for example.
The following Nginx location works just fine, but that's because set_by_lua_block() is a blocking function call:
location ~ \.php {
set $hello '';
set_by_lua_block $hello {
return "hello there.";
}
fastcgi_param HELLO $hello;
include fastcgi_params;
...
fastcgi_pass unix:/run/php/php7.0-fpm.sock;
}
My question is, what is the best approach here? Is there a way to call the Nginx directive fastcgi_pass
and related directives from within a content_by_lua_block() only after my variables have been set?