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.

1 files changed, 4 insertions, 2 deletions

diff --git a/src/http/ngx_http_cache.h b/src/http/ngx_http_cache.h
index 2a2d72291..193a35322 100644
--- a/src/http/ngx_http_cache.h
+++ b/src/http/ngx_http_cache.h
@@ -19,8 +19,9 @@
 #define NGX_HTTP_CACHE_EXPIRED       3
 #define NGX_HTTP_CACHE_STALE         4
 #define NGX_HTTP_CACHE_UPDATING      5
-#define NGX_HTTP_CACHE_HIT           6
-#define NGX_HTTP_CACHE_SCARCE        7
+#define NGX_HTTP_CACHE_REVALIDATED   6
+#define NGX_HTTP_CACHE_HIT           7
+#define NGX_HTTP_CACHE_SCARCE        8
 
 #define NGX_HTTP_CACHE_KEY_LEN       16
 
@@ -143,6 +144,7 @@ void ngx_http_file_cache_create_key(ngx_http_request_t *r);
 ngx_int_t ngx_http_file_cache_open(ngx_http_request_t *r);
 void ngx_http_file_cache_set_header(ngx_http_request_t *r, u_char *buf);
 void ngx_http_file_cache_update(ngx_http_request_t *r, ngx_temp_file_t *tf);
+void ngx_http_file_cache_update_header(ngx_http_request_t *r);
 ngx_int_t ngx_http_cache_send(ngx_http_request_t *);
 void ngx_http_file_cache_free(ngx_http_cache_t *c, ngx_temp_file_t *tf);
 time_t ngx_http_file_cache_valid(ngx_array_t *cache_valid, ngx_uint_t status);