commit 1ac2693a33bb65c6b0d777584ad8024aa743ee88
author Maxim Dounin <mdounin@mdounin.ru> Mon Nov 18 20:48:22 2013 +0400
committer Maxim Dounin <mdounin@mdounin.ru> Mon Nov 18 20:48:22 2013 +0400
tree 3cf6108d0daf072726805e4379fde73af0818201
parent df2fc6a9df06dcf334000a66c1173413883e1aba

Upstream: cache revalidation with conditional requests.

The following new directives are introduced: proxy_cache_revalidate,
fastcgi_cache_revalidate, scgi_cache_revalidate, uwsgi_cache_revalidate.
Default is off.  When set to on, they enable cache revalidation using
conditional requests with If-Modified-Since for expired cache items.

As of now, no attempts are made to merge headers given in a 304 response
during cache revalidation with headers previously stored in a cache item.
Headers in a 304 response are only used to calculate new validity time
of a cache item.

src/http/modules/ngx_http_proxy_module.c

diff --git a/src/http/modules/ngx_http_proxy_module.c b/src/http/modules/ngx_http_proxy_module.c
index cf68711..4046075 100644
--- a/src/http/modules/ngx_http_proxy_module.c
+++ b/src/http/modules/ngx_http_proxy_module.c
@@ -465,6 +465,13 @@
       offsetof(ngx_http_proxy_loc_conf_t, upstream.cache_lock_timeout),
       NULL },
 
+    { ngx_string("proxy_cache_revalidate"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_proxy_loc_conf_t, upstream.cache_revalidate),
+      NULL },
+
 #endif
 
     { ngx_string("proxy_temp_path"),
@@ -622,7 +629,8 @@
     { ngx_string("Keep-Alive"), ngx_string("") },
     { ngx_string("Expect"), ngx_string("") },
     { ngx_string("Upgrade"), ngx_string("") },
-    { ngx_string("If-Modified-Since"), ngx_string("") },
+    { ngx_string("If-Modified-Since"),
+      ngx_string("$upstream_cache_last_modified") },
     { ngx_string("If-Unmodified-Since"), ngx_string("") },
     { ngx_string("If-None-Match"), ngx_string("") },
     { ngx_string("If-Match"), ngx_string("") },
@@ -2454,6 +2462,7 @@
     conf->upstream.cache_valid = NGX_CONF_UNSET_PTR;
     conf->upstream.cache_lock = NGX_CONF_UNSET;
     conf->upstream.cache_lock_timeout = NGX_CONF_UNSET_MSEC;
+    conf->upstream.cache_revalidate = NGX_CONF_UNSET;
 #endif
 
     conf->upstream.hide_headers = NGX_CONF_UNSET_PTR;
@@ -2710,6 +2719,9 @@
     ngx_conf_merge_msec_value(conf->upstream.cache_lock_timeout,
                               prev->upstream.cache_lock_timeout, 5000);
 
+    ngx_conf_merge_value(conf->upstream.cache_revalidate,
+                              prev->upstream.cache_revalidate, 0);
+
 #endif
 
     ngx_conf_merge_str_value(conf->method, prev->method, "");