send 304 header by this module

[lloydzhou]

i make one location, to using lua code, and check the Etag to send 304 status code. but when i use this module to cache this location, it always hit the cache, and send 200 status code, also send the body every time.

[lloydzhou]

I make some mistake..... please just close this issue.

[lloydzhou]

i have read source code "ngx_http_srcache_fetch.c", this module just send 304 when check the "r->headers_out.last_modified_time".

i want to add check for etag.

[lloydzhou]

i have fork you code, and add the etag check in "ngx_http_srcache_fetch.c". you can review the code here https://github.com/lloydzhou/srcache-nginx-module/commit/d5303ac35ea99f253e0c01f309182cba25dc9543.

[lloydzhou]

may be we no need to check if modified or not, when hit the cache in "srcache_fetch". if hit cache, the response data from cache always the latest data. so, if user send any header to check if modified, just send 304 status. is this right?

[agentzh]

@lloydzhou I've just committed a fix to git master of this module so that it no longer bypasses the standard ngx_not_modified module's header filter. That way ngx_srcache supports both If-Modified-Since (for Last-Modified) and If-None-Match (for ETag) request headers out of the box.

The following test case demonstrates the usage:

https://github.com/openresty/srcache-nginx-module/blob/master/t/etag.t#L80

Please try it out on your side and let me know if it works for you.

But please note that due to a bug in the NGINX core, the Last-modified response header is required for ETag to take effect, see

http://osdir.com/ml/nginx/2013-11/msg00015.html

BTW, the suggestion in your last comment is not valid because browser-side cache and server-side cache may have different TTL settings (not to mention it also breaks RFC rules horribly).

[lloydzhou]

good job!!!

[lloydzhou]

i have update code, using master branch code. but some times the ngx_srcache module do not store the response body, only http headers...

this is my config: \ outner location:

        location ~ '/api/(.*)' {
            set $key $uri;
            set_escape_uri $escaped_key $key;
            srcache_fetch GET /redis $key;
            srcache_store PUT /redis2 key=$escaped_key&exptime=60*60;

            add_header X-Fetch-Status $srcache_fetch_status;
            add_header X-Store-Status $srcache_store_status;

            add_header Access-Control-Allow-Origin '*';
            add_header Access-Control-Allow-Methods 'PUT, POST, GET, OPTIONS';
            add_header Access-Control-Allow-Headers 'X-Requested-With';
            add_header Access-Control-Allow-Credentials 'true';

            header_filter_by_lua 'ngx.header.Content_Type="application/json; charset=utf-8;" ngx.header.Etag = ngx.time(); ngx.header.Last_Modified = ngx.http_time(ngx.time()+60*60);';
            echo_location '/internal/$1';
        }

\ internal location:

        location ~ '/internal/user/([0-9]+)'{
            drizzle_query 'select * from users where id=$1';
            drizzle_pass backend;
            rds_json on;
        }

some times i get 200 status code, and not get the body...the "X-Fetch-Status" is "HIT", and the "X-Store-Status" is "BYPASS"... so i check the reids, and see there's only http header, no http body stored...

redis 127.7.97.4:16379> get 7924bb905466929097060e3b256878d7
"HTTP/1.1 200 OK\r\nContent-Type: application/json; charset=utf-8;\r\nEtag: 1398786039\r\nLast-Modified: Tue, 29 Apr 2014 16:40:39 GMT\r\n\r\n"
redis 127.7.97.4:16379> get 4d2bf7b90748140382303e0dff53378a
"HTTP/1.1 200 OK\r\nContent-Type: application/json; charset=utf-8;\r\nEtag: 1398786066\r\nLast-Modified: Tue, 29 Apr 2014 16:41:06 GMT\r\n\r\n"

[agentzh]

@lloydzhou For your latest issue, to quote the related part in ngx_srcache's official documentation:

"The srcache_store directive can not be used to capture the responses generated by echo-nginx-module's subrequest directivees like echo_subrequest_async and echo_location."

See https://github.com/openresty/srcache-nginx-module#known-issues

And this is due to the internal limiation in the nginx core and I can do nothing about it on my side.

You're recommended to use the ngx_lua module to initiate and capture subrequests, which should work with ngx_srcache. Because you'll use Lua to do subrequests to ngx_drizzle anyway, you're recommended to use the lua-resty-mysql library instead, which should be more efficient (and also simpler): https://github.com/openresty/lua-resty-mysql#readme

[lloydzhou]

thank you very much!

[agentzh]

Consider it resolved.