proxy_cache not work for 204 responses

[Cícero Verneck Corrêa]

Nginx configuration for the application:

location / {
	uwsgi_pass		unix:/var/tmp/x.sock;
	uwsgi_cache		palco_cache;
	uwsgi_cache_valid	404 1m;
	uwsgi_cache_valid	302 8h;
	uwsgi_cache_valid	200 204 7d;
	uwsgi_cache_key		$uri$is_args$args;
	uwsgi_cache_lock	on;
	uwsgi_cache_use_stale	error updating timeout invalid_header http_500;
	uwsgi_cache_purge	PURGE from all;
	include			uwsgi_params;
	add_header		X-Cache $upstream_cache_status;
	uwsgi_ignore_headers	"Expires" "Cache-Control";
}

The test application has a page that returns 200 and a content whatsoever, and another that returns 204 with the contents empty.

Below lay the answer to both.

204 HEADER:

HTTP/1.1 204 NO CONTENT
Connection: keep-alive
Content-Length: 0
Content-Type: text/html; charset=utf-8
Date: Fri, 04 Jan 2013 21:19:51 GMT
Server: nginx
X-Cache: MISS

200 HEADER:

HTTP/1.1 200 OK
Connection: keep-alive
Content-Encoding: gzip
Content-Type: text/html; charset=utf-8
Date: Fri, 04 Jan 2013 21:37:00 GMT
Server: nginx
Transfer-Encoding: chunked
Vary: Accept-Encoding
X-Cache: HIT

No matter the number of requests, a request that returns 204 is never cached.

[Maxim Dounin]

Works fine here (though I tested it with proxy as in ticket summary, not uwsgi as in your config):

$ env TEST_NGINX_VERBOSE=1 prove -v proxy_cache.t
proxy_cache.t .. 
1..12
# >> GET /204 HTTP/1.0\x0a
# >> Host: localhost\x0a
# >> \x0a
# << HTTP/1.1 204 No Content\x0d\x0a
# << Server: nginx/1.3.10\x0d\x0a
# << Date: Sat, 05 Jan 2013 13:27:43 GMT\x0d\x0a
# << Connection: close\x0d\x0a
# << X-Cache-Status: MISS\x0d\x0a
# << \x0d\x0a
ok 1 - proxy request 204
# >> GET /204 HTTP/1.0\x0a
# >> Host: localhost\x0a
# >> \x0a
# << HTTP/1.1 204 No Content\x0d\x0a
# << Server: nginx/1.3.10\x0d\x0a
# << Date: Sat, 05 Jan 2013 13:27:43 GMT\x0d\x0a
# << Connection: close\x0d\x0a
# << X-Cache-Status: HIT\x0d\x0a
# << \x0d\x0a
ok 2 - proxy request 204 cached
...

With the following patch for the ​test suite:

--- a/proxy_cache.t
+++ b/proxy_cache.t
@@ -59,6 +59,8 @@ http {
 
             proxy_cache_use_stale  error timeout invalid_header http_500
                                    http_404;
+
+            add_header X-Cache-Status $upstream_cache_status;
         }
 
         location /fake/ {
@@ -72,6 +74,10 @@ http {
 
         location / {
         }
+
+        location = /204 {
+            return 204;
+        }
     }
 }
 
@@ -85,6 +91,9 @@ EOF
 
 ###############################################################################
 
+like(http_get('/204'), qr/MISS/, 'proxy request 204');
+like(http_get('/204'), qr/HIT/, 'proxy request 204 cached');
+
 like(http_get('/t.html'), qr/SEE-THIS/, 'proxy request');
 
 $t->write_file('t.html', 'NOOP');

You may want make sure you are able to reproduce the problem without 3rd party modules/patches, and provide debug log with two requests to 204 to see what goes wrong in your case (see ​http://nginx.org/en/docs/debugging_log.html).

[Maxim Dounin]

Feedback timeout.