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为什么不缓存同一图像的第二次和第三次请求？

2017-02-10 147 views
0

原始网站没有按照我认为应该的方式缓存html，css或图片。下面是谷歌Chrome浏览器仅用于一张图片，同时请求网站上的不同页面的结果。它是一个网站的更大浏览的一部分，试图找出为什么浏览器认为它应该被缓存，但浏览器是从服务器重新请求。我删除了所有与这个图像没有特别关系的har。为什么不缓存同一图像的第二次和第三次请求？

我没有任何cache-killer或cache-disabler。我甚至去了相对干净的电脑，以确保没有安装任何可能与缓存混淆的开发工具。

第一个请求中的所有请求/响应头似乎暗示第二个和第三个请求不应该发出重新请求，而是来自浏览器本地缓存。

我错过了什么？

{ 
    "startedDateTime": "2017-02-10T21:21:44.273Z", 
    "time": 56.46199999999624, 
    "request": { 
     "method": "GET", 
     "url": "http://616206ee2c1b2155fd11-21abbde6fa52e03b7fd037b3488bb991.r53.cf1.rackcdn.com/images/default-source/site-cdn/LoginLogo.png", 
     "httpVersion": "HTTP/1.1", 
     "headers": [ 
     { 
      "name": "Accept", 
      "value": "image/webp,image/*,*/*;q=0.8" 
     }, 
     { 
      "name": "Connection", 
      "value": "keep-alive" 
     }, 
     { 
      "name": "Accept-Encoding", 
      "value": "gzip, deflate, sdch" 
     }, 
     { 
      "name": "Referer", 
      "value": "http://authentrip.com/" 
     }, 
     { 
      "name": "Host", 
      "value": "616206ee2c1b2155fd11-21abbde6fa52e03b7fd037b3488bb991.r53.cf1.rackcdn.com" 
     }, 
     { 
      "name": "Accept-Language", 
      "value": "en-US,en;q=0.8" 
     }, 
     { 
      "name": "User-Agent", 
      "value": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36" 
     } 
     ], 
     "queryString": [], 
     "cookies": [], 
     "headersSize": 428, 
     "bodySize": 0 
    }, 
    "response": { 
     "status": 200, 
     "statusText": "OK", 
     "httpVersion": "HTTP/1.1", 
     "headers": [ 
     { 
      "name": "Date", 
      "value": "Fri, 10 Feb 2017 21:21:44 GMT" 
     }, 
     { 
      "name": "Origin", 
      "value": "https://mycloud.rackspace.com" 
     }, 
     { 
      "name": "Last-Modified", 
      "value": "Fri, 09 Dec 2016 05:10:48 GMT" 
     }, 
     { 
      "name": "ETag", 
      "value": "ab904584a8e355da2fd0437065839e10" 
     }, 
     { 
      "name": "Content-Type", 
      "value": "image/png" 
     }, 
     { 
      "name": "X-Timestamp", 
      "value": "1481260247.52133" 
     }, 
     { 
      "name": "Cache-Control", 
      "value": "public, max-age=349" 
     }, 
     { 
      "name": "Content-Length", 
      "value": "6397" 
     }, 
     { 
      "name": "Connection", 
      "value": "keep-alive" 
     }, 
     { 
      "name": "Accept-Ranges", 
      "value": "bytes" 
     }, 
     { 
      "name": "X-Trans-Id", 
      "value": "txbeec00752b6a4e1e9e3b5-00589e2ca4dfw1" 
     }, 
     { 
      "name": "Expires", 
      "value": "Fri, 10 Feb 2017 21:27:33 GMT" 
     } 
     ], 
     "cookies": [], 
     "content": { 
     "size": 6397, 
     "mimeType": "image/png", 
     "compression": 0 
     }, 
     "redirectURL": "", 
     "headersSize": 433, 
     "bodySize": 6397, 
     "_transferSize": 6830 
    }, 
    "cache": {}, 
    "timings": { 
     "blocked": 0.396999999992431, 
     "dns": -1, 
     "connect": -1, 
     "send": 0.13800000000685503, 
     "wait": 23.861999999994016, 
     "receive": 32.06500000000294, 
     "ssl": -1 
    }, 
    "serverIPAddress": "204.2.145.184", 
    "connection": "989", 
    "pageref": "page_1" 
    }, 
    { 
    "startedDateTime": "2017-02-10T21:22:48.357Z", 
    "time": 0, 
    "request": { 
     "method": "GET", 
     "url": "http://616206ee2c1b2155fd11-21abbde6fa52e03b7fd037b3488bb991.r53.cf1.rackcdn.com/images/default-source/site-cdn/LoginLogo.png", 
     "httpVersion": "HTTP/1.1", 
     "headers": [ 
     { 
      "name": "Accept", 
      "value": "image/webp,image/*,*/*;q=0.8" 
     }, 
     { 
      "name": "Connection", 
      "value": "keep-alive" 
     }, 
     { 
      "name": "Accept-Encoding", 
      "value": "gzip, deflate, sdch" 
     }, 
     { 
      "name": "Referer", 
      "value": "http://authentrip.com/" 
     }, 
     { 
      "name": "Host", 
      "value": "616206ee2c1b2155fd11-21abbde6fa52e03b7fd037b3488bb991.r53.cf1.rackcdn.com" 
     }, 
     { 
      "name": "Accept-Language", 
      "value": "en-US,en;q=0.8" 
     }, 
     { 
      "name": "User-Agent", 
      "value": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36" 
     } 
     ], 
     "queryString": [], 
     "cookies": [], 
     "headersSize": 428, 
     "bodySize": 0 
    }, 
    "response": { 
     "status": 200, 
     "statusText": "OK", 
     "httpVersion": "HTTP/1.1", 
     "headers": [ 
     { 
      "name": "Date", 
      "value": "Fri, 10 Feb 2017 21:21:44 GMT" 
     }, 
     { 
      "name": "Origin", 
      "value": "https://mycloud.rackspace.com" 
     }, 
     { 
      "name": "Last-Modified", 
      "value": "Fri, 09 Dec 2016 05:10:48 GMT" 
     }, 
     { 
      "name": "ETag", 
      "value": "ab904584a8e355da2fd0437065839e10" 
     }, 
     { 
      "name": "Content-Type", 
      "value": "image/png" 
     }, 
     { 
      "name": "X-Timestamp", 
      "value": "1481260247.52133" 
     }, 
     { 
      "name": "Cache-Control", 
      "value": "public, max-age=349" 
     }, 
     { 
      "name": "Content-Length", 
      "value": "6397" 
     }, 
     { 
      "name": "Connection", 
      "value": "keep-alive" 
     }, 
     { 
      "name": "Accept-Ranges", 
      "value": "bytes" 
     }, 
     { 
      "name": "X-Trans-Id", 
      "value": "txbeec00752b6a4e1e9e3b5-00589e2ca4dfw1" 
     }, 
     { 
      "name": "Expires", 
      "value": "Fri, 10 Feb 2017 21:27:33 GMT" 
     } 
     ], 
     "cookies": [], 
     "content": { 
     "size": 6397, 
     "mimeType": "image/png" 
     }, 
     "redirectURL": "", 
     "headersSize": 433, 
     "bodySize": 0, 
     "_transferSize": 0 
    }, 
    "cache": {}, 
    "timings": { 
     "blocked": -1, 
     "dns": -1, 
     "connect": -1, 
     "send": 0, 
     "wait": 0, 
     "receive": 0, 
     "ssl": -1 
    }, 
    "serverIPAddress": "204.2.145.184", 
    "connection": "989", 
    "pageref": "page_2" 
    } 
    { 
    "startedDateTime": "2017-02-10T21:23:38.412Z", 
    "time": 0, 
    "request": { 
     "method": "GET", 
     "url": "http://616206ee2c1b2155fd11-21abbde6fa52e03b7fd037b3488bb991.r53.cf1.rackcdn.com/images/default-source/site-cdn/LoginLogo.png", 
     "httpVersion": "HTTP/1.1", 
     "headers": [ 
     { 
      "name": "Accept", 
      "value": "image/webp,image/*,*/*;q=0.8" 
     }, 
     { 
      "name": "Connection", 
      "value": "keep-alive" 
     }, 
     { 
      "name": "Accept-Encoding", 
      "value": "gzip, deflate, sdch" 
     }, 
     { 
      "name": "Referer", 
      "value": "http://authentrip.com/" 
     }, 
     { 
      "name": "Host", 
      "value": "616206ee2c1b2155fd11-21abbde6fa52e03b7fd037b3488bb991.r53.cf1.rackcdn.com" 
     }, 
     { 
      "name": "Accept-Language", 
      "value": "en-US,en;q=0.8" 
     }, 
     { 
      "name": "User-Agent", 
      "value": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36" 
     } 
     ], 
     "queryString": [], 
     "cookies": [], 
     "headersSize": 428, 
     "bodySize": 0 
    }, 
    "response": { 
     "status": 200, 
     "statusText": "OK", 
     "httpVersion": "HTTP/1.1", 
     "headers": [ 
     { 
      "name": "Date", 
      "value": "Fri, 10 Feb 2017 21:21:44 GMT" 
     }, 
     { 
      "name": "Origin", 
      "value": "https://mycloud.rackspace.com" 
     }, 
     { 
      "name": "Last-Modified", 
      "value": "Fri, 09 Dec 2016 05:10:48 GMT" 
     }, 
     { 
      "name": "ETag", 
      "value": "ab904584a8e355da2fd0437065839e10" 
     }, 
     { 
      "name": "Content-Type", 
      "value": "image/png" 
     }, 
     { 
      "name": "X-Timestamp", 
      "value": "1481260247.52133" 
     }, 
     { 
      "name": "Cache-Control", 
      "value": "public, max-age=349" 
     }, 
     { 
      "name": "Content-Length", 
      "value": "6397" 
     }, 
     { 
      "name": "Connection", 
      "value": "keep-alive" 
     }, 
     { 
      "name": "Accept-Ranges", 
      "value": "bytes" 
     }, 
     { 
      "name": "X-Trans-Id", 
      "value": "txbeec00752b6a4e1e9e3b5-00589e2ca4dfw1" 
     }, 
     { 
      "name": "Expires", 
      "value": "Fri, 10 Feb 2017 21:27:33 GMT" 
     } 
     ], 
     "cookies": [], 
     "content": { 
     "size": 6397, 
     "mimeType": "image/png" 
     }, 
     "redirectURL": "", 
     "headersSize": 433, 
     "bodySize": 0, 
     "_transferSize": 0 
    }, 
    "cache": {}, 
    "timings": { 
     "blocked": -1, 
     "dns": -1, 
     "connect": -1, 
     "send": 0, 
     "wait": 0, 
     "receive": 0, 
     "ssl": -1 
    }, 
    "serverIPAddress": "204.2.145.184", 
    "connection": "989", 
    "pageref": "page_3" 
    }

来源

2017-02-10 DFBerry

回答

1

事实上，Chrome确实为来自缓存的第二个和第三个请求提供了响应。你需要看看entry.response.bodySize属性。

从HAR specification相关摘录：

bodySize [数字] - 所接收的响应主体的以字节为单位的大小。如果响应来自缓存（304），则设置为零。如果信息不可用，则设置为-1。

也有趣的是HAR Viewer GitHub issue。他们使用下面的函数来确定是否响应请求是从缓存服务的：

HarModel.isCachedEntry = function(entry) { 
    var response = entry.response; 
    var resBodySize = response.bodySize > 0 ? response.bodySize : 0; 
    return (response.status == 304 || (resBodySize === 0 && response.content && response.content.size > 0)); 
};

来源

2017-02-13 08:51:24

+0

谢谢。它应该从缓存中提供，但我无法'看到'发生了什么。很高兴得到答案 – DFBerry

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