# HG changeset patch
# User Piotr Sikora <piotr@cloudflare.com>
# Date 1416359233 28800
# Tue Nov 18 17:07:13 2014 -0800
# Node ID 16f4ca8391ddd98ba99b00a46c0b56390f38e0a2
# Parent 99e65578bc80960b2fdf494e048678dd97bba029
Cache: send conditional requests only for cached 200 OK responses.

RFC7232 says:

The 304 (Not Modified) status code indicates that a conditional GET
or HEAD request has been received and would have resulted in a 200
(OK) response if it were not for the fact that the condition
evaluated to false.

which means that there is no reason to send requests with "If-None-Match"
and/or "If-Modified-Since" headers for responses cached with other status
codes.

Also, sending conditional requests for responses cached with other status
codes could result in a strange behavior, e.g. upstream server returning
304 Not Modified for cached 404 Not Found responses, etc.

Signed-off-by: Piotr Sikora <piotr@cloudflare.com>

diff -r 99e65578bc80 -r 16f4ca8391dd src/http/ngx_http_cache.h
--- a/src/http/ngx_http_cache.h Tue Nov 18 17:07:13 2014 -0800
+++ b/src/http/ngx_http_cache.h Tue Nov 18 17:07:13 2014 -0800
@@ -27,7 +27,7 @@
#define NGX_HTTP_CACHE_ETAG_LEN 42
#define NGX_HTTP_CACHE_VARY_LEN 42

-#define NGX_HTTP_CACHE_VERSION 4
+#define NGX_HTTP_CACHE_VERSION 5


typedef struct {
@@ -83,6 +83,7 @@ struct ngx_http_cache_s {

ngx_uint_t min_uses;
ngx_uint_t error;
+ ngx_uint_t status;

ngx_buf_t *buf;

@@ -114,6 +115,7 @@ typedef struct {
time_t last_modified;
time_t date;
uint32_t crc32;
+ u_short status;
u_short header_start;
u_short body_start;
u_char etag_len;
diff -r 99e65578bc80 -r 16f4ca8391dd src/http/ngx_http_file_cache.c
--- a/src/http/ngx_http_file_cache.c Tue Nov 18 17:07:13 2014 -0800
+++ b/src/http/ngx_http_file_cache.c Tue Nov 18 17:07:13 2014 -0800
@@ -561,6 +561,7 @@ ngx_http_file_cache_read(ngx_http_reques
c->valid_sec = h->valid_sec;
c->last_modified = h->last_modified;
c->date = h->date;
+ c->status = h->status;
c->header_start = h->header_start;
c->body_start = h->body_start;
c->etag.len = h->etag_len;
@@ -1117,6 +1118,7 @@ ngx_http_file_cache_set_header(ngx_http_
h->last_modified = c->last_modified;
h->date = c->date;
h->crc32 = c->crc32;
+ h->status = (u_short) c->status;
h->header_start = (u_short) c->header_start;
h->body_start = (u_short) c->body_start;

@@ -1335,6 +1337,7 @@ ngx_http_file_cache_update_header(ngx_ht
if (h.version != NGX_HTTP_CACHE_VERSION
|| h.last_modified != c->last_modified
|| h.crc32 != c->crc32
+ || h.status != c->status
|| h.header_start != c->header_start
|| h.body_start != c->body_start)
{
@@ -1356,6 +1359,7 @@ ngx_http_file_cache_update_header(ngx_ht
h.last_modified = c->last_modified;
h.date = c->date;
h.crc32 = c->crc32;
+ h.status = (u_short) c->status;
h.header_start = (u_short) c->header_start;
h.body_start = (u_short) c->body_start;

diff -r 99e65578bc80 -r 16f4ca8391dd src/http/ngx_http_upstream.c
--- a/src/http/ngx_http_upstream.c Tue Nov 18 17:07:13 2014 -0800
+++ b/src/http/ngx_http_upstream.c Tue Nov 18 17:07:13 2014 -0800
@@ -2560,6 +2560,7 @@ ngx_http_upstream_send_response(ngx_http
}

if (valid) {
+ r->cache->status = u->headers_in.status_n;
r->cache->last_modified = u->headers_in.last_modified_time;
r->cache->date = now;
r->cache->body_start = (u_short) (u->buffer.pos - u->buffer.start);
@@ -4924,6 +4925,7 @@ ngx_http_upstream_cache_last_modified(ng
if (r->upstream == NULL
|| !r->upstream->conf->cache_revalidate
|| r->upstream->cache_status != NGX_HTTP_CACHE_EXPIRED
+ || r->cache->status != NGX_HTTP_OK
|| r->cache->last_modified == -1)
{
v->not_found = 1;
@@ -4952,6 +4954,7 @@ ngx_http_upstream_cache_etag(ngx_http_re
if (r->upstream == NULL
|| !r->upstream->conf->cache_revalidate
|| r->upstream->cache_status != NGX_HTTP_CACHE_EXPIRED
+ || r->cache->status != NGX_HTTP_OK
|| r->cache->etag.len == 0)
{
v->not_found = 1;

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