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, 2 insertions, 0 deletions

diff --git a/src/http/ngx_http_upstream.h b/src/http/ngx_http_upstream.h
index fd4e36b1f..469988eed 100644
--- a/src/http/ngx_http_upstream.h
+++ b/src/http/ngx_http_upstream.h
@@ -178,6 +178,8 @@ typedef struct {
     ngx_flag_t                       cache_lock;
     ngx_msec_t                       cache_lock_timeout;
 
+    ngx_flag_t                       cache_revalidate;
+
     ngx_array_t                     *cache_valid;
     ngx_array_t                     *cache_bypass;
     ngx_array_t                     *no_cache;