Question

最近几个小时，我试图弄明白，为什么在第一次请求后，浏览器中没有缓存以下图片：

http://runrpg.net/assets/images/screenshots/placeit_outdoor_wide.jpg

我知道必须设置正确的标头，目前响应标头如下所示：

HTTP/1.1 200 OK
Date: Sat, 04 Jan 2014 16:35:53 GMT
Server: Apache/2.4.4 (Unix) OpenSSL/1.0.1e PHP/5.5.3 mod_perl/2.0.8-dev
    Perl/v5.16.3
Last-Modified: Sat, 30 Nov 2013 01:37:52 GMT
ETag: "1dac5-4ec5afebf3c00-gzip"
Accept-Ranges: bytes
Cache-Control: max-age=2592000
Expires: Mon, 03 Feb 2014 16:35:53 GMT
Vary: Accept-Encoding
Content-Encoding: gzip
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Transfer-Encoding: chunked
Content-Type: image/jpeg

如您所见，“Expires”标题设置为“Mon，03 Feb 2014 16:35:53 GMT”，我还包括“Cache-Control：max-age = 2592000”。

你可以帮助我，告诉我我错过了什么吗？非常感谢您的帮助。

谢谢！

Answer 1

这很可能是由于您的服务器未正确验证ETag。通过Last-Modified标头进行缓存验证效果很好：

$ HEAD -H "If-Modified-Since: Sat, 30 Nov 2013 01:37:52 GMT" http://runrpg.net/assets/images/screenshots/placeit_outdoor_wide.jpg
304 Not Modified
Cache-Control: max-age=290304000, public
Connection: close
Date: Sat, 04 Jan 2014 19:01:30 GMT
ETag: "1dac5-4ec5afebf3c00"
Server: Apache/2.4.4 (Unix) OpenSSL/1.0.1e PHP/5.5.3 mod_perl/2.0.8-dev Perl/v5.16.3
Expires: Thu, 09 Jan 2014 19:01:30 GMT
Client-Date: Sat, 04 Jan 2014 19:01:30 GMT
Client-Peer: 80.70.3.110:80
Client-Response-Num: 1

同样不能用ETags说：

$ HEAD -H 'If-None-Match: "1dac5-4ec5afebf3c00-gzip"' http://runrpg.net/assets/images/screenshots/placeit_outdoor_wide.jpg
200 OK
Cache-Control: max-age=290304000, public
Connection: close
Date: Sat, 04 Jan 2014 19:02:24 GMT
Accept-Ranges: bytes
ETag: "1dac5-4ec5afebf3c00"
Server: Apache/2.4.4 (Unix) OpenSSL/1.0.1e PHP/5.5.3 mod_perl/2.0.8-dev Perl/v5.16.3
Vary: Accept-Encoding
Content-Length: 121541
Content-Type: image/jpeg
Expires: Thu, 09 Jan 2014 19:02:24 GMT
Last-Modified: Sat, 30 Nov 2013 01:37:52 GMT
Access-Control-Allow-Credentials: true
Access-Control-Allow-Headers: origin, x-requested-with, content-type, X-Titanium-Id
Access-Control-Allow-Methods: PUT, GET, POST, DELETE, OPTIONS
Access-Control-Allow-Origin: http://127.0.0.1:8020
Client-Date: Sat, 04 Jan 2014 19:02:24 GMT
Client-Peer: 80.70.3.110:80
Client-Response-Num: 1

底线：问题是您的服务器，而不是任何客户端。这似乎是Apache 2.4.x的known issue。对此的快速解决方案是关闭ETag：

FileETag None

即使设置了标头，图像也不会存储在缓存中

1 个答案: