Notes on the nphase module
---

To install, compile nginx with this ./configure option:

    --add-module=path/to/this/directory

This module is an experimental module for providing a distribute file system by
nginx. There are two phases processed looply.

Phase 1: send a subrequest to backend to query file position. In case of 200 
code, the subrequest would write data to client. In case of 302 code, the main 
request would request backend by Location header line returning, and go into 
phase 2 process.

Phase 2: send a subrequest to backend to download file, only 200 or 206 
should be accepted. If downstream sent length equal to request range, the 
request finished. Otherwise, main request would go to phase 1 and set request 
range by sent length and file size parsed from header string(X-NP-File-Size) 
from phase 1 backend.

Given that large files stored in many backend servers. The large files are 
split into many small segments, and the meta information stored in a chunk 
server(eg. GFS). This module acts as a fronted proxy for downloading files
by http.

nginx.conf file example:

        location /down {
            nphase_uri /dummy;
            nphase_set_uri_var $np_uri;
            nphase_set_range_var $np_range;
            set $np_uri http://10.1.1.10;
            set $np_range "bytes=0-";
        }

        location /dummy {
            proxy_pass $np_uri;
            proxy_set_header Range $np_range;
        }


Changelogs
  v0.1
    *   first release