Hello.
I have a task of checking correctness of content, stored in nginx cache, so that users will not receive broken files (say, when there are problems on TCP level).
I want to accomplish this task by automatically computing MD5 value for file being stored and comparing it with Content-MD5 header that came with that file. If values mismatch - nginx should re-request file from origin server.

Question is - approximately how much time will it take to modify existing ngx_http_proxy_module or implement brand new module? Or maybe there is an easier way to accomplish this task?

Thanks!