I have implemented an H.264 pseudo streaming module. And now I want to add cache
feature to this module.

My situation is that we have some data centers across country, and each data
center has some servers to provide video clips to our users. >Because we want to
simplify the management of the storage and video files synchronization problem,
we maintain only one central storage. >The servers on edge data centers should
cache the most visited video clips based on LRU algorithm.

I read the ngx_httpd_proxy_module.c file, and I think it is a good starting
point. I know a simplified module capable of this cache >feature should work
like this: Step 1.if the requested file has been found on local disk, return the file Step 2.if the requested file has not been found on local disk, proxy this
request to original server and send the response to user and >save the file to
local disk.

I know I can implement Step 1 on ngx_http_proxy_handler function. For Step 2 I
know I should create the proxy request on >ngx_http_proxy_create_request
function, but I do NOT know on which function I can save the response file to
local disk and how. Should I >implement this feature on
ngx_http_proxy_finalize_request function? And which data structure contains the
returned file data, is it >u->buffering?