Chrome拒绝缓存Javascript [英] Chrome refuses to cache Javascript

问题描述

我对浏览器缓存很合适。我试图让Chrome浏览器使用查询参数永久缓存任何静态文件（用于缓存清除目的）。我已经将Cache-Control和Expires头文件设置为未来，这应该足以说永远缓存。产生的响应头文件：

 
 HTTP / 1.1 200 OK 
 Cache-Control：public，max-age = 315360000 
连接：keep-alive 
内容编码：gzip 
内容类型：application / x-javascript 
日期：2014年7月16日星期三09:29:54 GMT 
 Last -Modified：Wed，16 Jul 2014 03:44:14 GMT 
 Server：nginx / 1.6.0 
 Transfer-Encoding：chunked 
 Vary：Accept-Encoding 
 

Firefox和Safari似乎对所有cachebusted（？v =查询参数）文件都表示尊重。 Chrome主要遵循指令，除了Javascript。大多数情况下，它使用If-Modified-Since标头执行请求，而不是从缓存中加载。有时候，其中一个会从缓存中加载，另一个会产生一个导致304的请求。通常，当从新选项卡加载页面时，它将从缓存中加载，但如果您在地址栏中输入，则不会。

我观察到其他网站使用我认为完全相同的标题，并且文件始终从缓存中加载。我知道缓存行为有点不可预知，但我想确保我不会监督正在做的事情Chrome做到了这一点？

解决方案

我在chrome中遇到了同样的问题，经过几个小时的试验和错误，我发现，似乎有一个与Vary Header的问题

我在我的Apache / .htaccess配置中有这个片段，并且只要我评论这行Header append Vary Accept -EncodingChrome开始缓存.js和.css文件

 < FilesMatch（\.js\.gz | \.css\.gz）$> 
＃服务正确的编码类型。 
头文件集内容编码gzip 
＃强制代理缓存gzipped&非gzip的CSS / JS文件分开。 
 #Header append Vary接受编码
< / FilesMatch> 
  

在通过我们的nignx服务器运行请求时，它仍然不起作用，因为它添加了Vary： Accept-Encoding header，当提供gzip压缩时。

到目前为止，我可以猜测这是一个只会发生在Chrome上的问题，作为一种解决方法，我会将配置更改为只有在chrome（没有检查过safari）不是客户端之前追加标题，直到有更好的解决方案：

 << ; FilesMatch（\.js\.gz | \.css\.gz）$> 
＃服务正确的编码类型。 
头文件集内容编码gzip 
＃强制代理缓存gzipped&非gzip的CSS / JS文件分开。 
 BrowserMatchChromeChromeFound 
标题附加内容Vary Accept-Encoding env =！ChromeFound 
  
  

I am reasonably new to browser caching. I am attempting to get Chrome to permanently cache any static file with a query parameter (for cache busting purposes). I have set Cache-Control and Expires headers way into the future, which should be adequate to say "cache this forever". The resulting response headers:

HTTP/1.1 200 OK
Cache-Control: public, max-age=315360000
Connection: keep-alive
Content-Encoding: gzip
Content-Type: application/x-javascript
Date: Wed, 16 Jul 2014 09:29:54 GMT
Last-Modified: Wed, 16 Jul 2014 03:44:14 GMT
Server: nginx/1.6.0
Transfer-Encoding: chunked
Vary: Accept-Encoding

Firefox and Safari seem to respect this for all cachebusted (?v= query parameter) files. Chrome mostly follows the directives, except for Javascript. Most of the time it does a request with an If-Modified-Since header rather than loading from cache. Sometimes one of them will load from cache and the other will yield a request resulting in a 304. Usually when loading the page from a new tab it will load from cache, but not if you hit enter in the address bar.

I've observed other websites using what I think are the exact same headers, and the files are always loaded from cache. Some of them load from cache even if you do a refresh.

I understand cache behaviour is somewhat unpredictable, but I want to make sure I'm not overseeing something that's making Chrome do that?

解决方案

I had the same issue with chrome and after some hours of trial and error I figuered out, that chrome seems to have a problem with the Vary Header

I've got this snippet in my Apache / .htaccess config and as soon as I comment the line "Header append Vary Accept-Encoding" Chrome starts caching .js and .css files

  <FilesMatch "(\.js\.gz|\.css\.gz)$">
  # Serve correct encoding type.
  Header set Content-Encoding gzip
  # Force proxies to cache gzipped & non-gzipped css/js files separately.
  #Header append Vary Accept-Encoding
</FilesMatch>

It still does not work while running the request via our nignx server, because it is adding the Vary: Accept-Encoding header too, when delivering gzip compressed.

So far I can guess this is a problem that only happens with chrome and as a workaround I would change the configuration to append the header only if chrome (haven't checked for safari) is not the client until there is a better fix:

<FilesMatch "(\.js\.gz|\.css\.gz)$">
  # Serve correct encoding type.
  Header set Content-Encoding gzip
  # Force proxies to cache gzipped & non-gzipped css/js files separately.
  BrowserMatch "Chrome" ChromeFound
  Header append Vary Accept-Encoding env=!ChromeFound
</FilesMatch>

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