details: http://hg.nginx.org/nginx/rev/1573fc7875fa
branches:
changeset: 5935:1573fc7875fa
user: Piotr Sikora <piotr@cloudflare.com>
date: Wed Nov 26 18:35:37 2014 -0800
description:
Cache: send conditional requests only for cached 200/206 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>

diffstat:

src/http/ngx_http_file_cache.c | 2 ++
src/http/ngx_http_upstream.c | 11 ++++++++---
2 files changed, 10 insertions(+), 3 deletions(-)

diffs (36 lines):

diff --git a/src/http/ngx_http_file_cache.c b/src/http/ngx_http_file_cache.c
--- a/src/http/ngx_http_file_cache.c
+++ b/src/http/ngx_http_file_cache.c
@@ -177,6 +177,8 @@ ngx_http_file_cache_new(ngx_http_request
c->file.log = r->connection->log;
c->file.fd = NGX_INVALID_FILE;

+ c->last_modified = -1;
+
return NGX_OK;
}

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -2565,12 +2565,17 @@ ngx_http_upstream_send_response(ngx_http
}

if (valid) {
- 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);

- if (u->headers_in.etag) {
- r->cache->etag = u->headers_in.etag->value;
+ if (u->headers_in.status_n == NGX_HTTP_OK
+ || u->headers_in.status_n == NGX_HTTP_PARTIAL_CONTENT)
+ {
+ r->cache->last_modified = u->headers_in.last_modified_time;
+
+ if (u->headers_in.etag) {
+ r->cache->etag = u->headers_in.etag->value;
+ }
}

ngx_http_file_cache_set_header(r, u->buffer.start);

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