Best method to create a c++ app to communicate with nginx

No one here seems to have addressed the actual question, though some nice work arounds have been offered. I've been able to build C++ modules for nginx with a couple of minor changes.

1. Change the module source file name to end with .cpp so gcc realizes it is dealing with C++.
2. Make sure all your Nginx includes (e.g. ngx_config.h, ngx_core.h, etc.) are wrapped with an extern "C" { } structure. Similarly make sure any functions called through Nginx function pointers are declared with a wrapper.
3. Add --with-ld-opt="-lstdc++" to your "configure" invocation when setting up Nginx.

With those three steps your module should compile, build, link, and actually work.

I think I will go forward with Nginx module devlopment http://www.evanmiller.org/nginx-modules-guide.html

Why ?

1. It don't require any other library dependency like fastcgi andother.
2. I can use all feature of nginx inside my module.

What you are asking is basically how to turn the c++ process that holds your data strutures into a webserver. That might not be the best way to go about it. (Then again, maybe it is in your situation. It depends on the complexity of the c++ process's interfaces you are trying to expose i guess.)

Anyways, I would try to stick a small http frontend in between the c++ process and the clients that could do the http work and communicate with the c++ backend process using some simple messaging protocol like ZeroMQ/zmq.

zmq in c/c++ is fairly straight forward, and its very efficient and very fast. Using zmq you could very quickly setup a simple webserver frontend in python, or whatever language you prefer that has zmq bindings, and have that frontend communicate asyncronously or syncronously with the backend c++ process using zmq.

The c++ examples and the guide are nice starting points if you are looking into using zmq.

For Node.js there are also a few examples.