gistfile1.c

static ngx_int_t my_http_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
{
     ngx_int_t                  rc;
     ngx_uint_t                 last;
     ngx_chain_t               *cl;
     ngx_http_request_t        *sr;
     ngx_str_t           uri = SOME_INTERNAL_URI;
 
     if (in == NULL || r->header_only ) {
         return ngx_http_next_body_filter(r, in);
     }

     /* check is it last chunk */
     /* http://www.evanmiller.org/nginx-modules-guide.html#filters-body */
     last = 0;
     for (cl = in; cl; cl = cl->next) {
         if (cl->buf->last_buf) {
             cl->buf->last_buf = 0;
             cl->buf->sync = 1;
             last = 1;
     }
 
     rc = ngx_http_next_body_filter(r, in);
 
    if (rc == NGX_ERROR || rc > NGX_OK || !last) {
        return rc;
    }

    if (r != r->main) {
        /* we are processing a subrequest */
        return rc
    }

     if (ngx_http_subrequest(r, &uri, NULL, &sr, NULL, 0) != NGX_OK) {
        /* the big difference with Evan's tutorial */
        /* but this is usual pattern in some modern modules */
         return NGX_ERROR;
     }

     return NGX_AGAIN;
 }