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当存在 Vary 标头时，Squid 代理拒绝重新验证缓存

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当存在 Vary 标头时，Squid 代理拒绝重新验证缓存

squid配置文件

cache_effective_user squid

http_access allow all

# Squid normally listens to port 3128
http_port 3128 accel defaultsite=localhost no-vhost ignore-cc

cache_peer localhost parent 80 0 no-query originserver name=myAccel
cache_peer_access myAccel allow all

# Uncomment and adjust the following to add a disk cache directory.
cache_dir ufs /usr/local/var/cache/squid 100 16 256

# Leave coredumps in the first cache dir
coredump_dir /usr/local/var/cache/squid

minimum_expiry_time 0

测试.php

<?php

Header( "Cache-Control: max-age=0, must-revalidate" ); 

$headers = getallheaders();
$ims = $headers['If-Modified-Since'];
$lastModified = "Mon, 16 Apr 2012 23:01:32 GMT";
if ($ims == $lastModified) {
    Header( "HTTP/1.1 304 Not Modified" ); 
    exit;
}

Header("Last-Modified: $lastModified");
if ($_GET["vary"]) Header("Vary: Accept-Encoding");

?><html>hi</html>

Squid 3.2.9，通过 Homebrew 安装在 OSX 上

Squid 3.2.9，通过 Homebrew 安装在 OSX 上

localhost: ~ $ squid -v
Squid Cache: Version 3.2.9
configure options:  '--disable-debug' '--disable-dependency-tracking' '--prefix=/usr/local/Cellar/squid/3.2.9' '--localstatedir=/usr/local/var' 'CC=cc' 'CXX=c++' 'PKG_CONFIG_LIBDIR=/usr/lib/pkgconfig'

开始用鱿鱼squid -f squid.conf -d 2 -N

当服务器忽略“Vary:Accept-Encoding”标头时，Squid 使用 If-Modified-Since 条件 GET 重新验证/刷新其缓存。但是当存在“Vary:Accept-Encoding”标头时，Squid 拒绝使用 If-Modified-Since，而是直接忽略其缓存。为什么？

localhost: ~ $ curl --silent -o /dev/null --dump-header /dev/stdout http://localhost:3128/test.php
HTTP/1.1 200 OK
Date: Wed, 17 Apr 2013 00:17:42 GMT
Server: Apache/2.2.22 (Unix) DAV/2 PHP/5.3.15 with Suhosin-Patch mod_ssl/2.2.22 OpenSSL/0.9.8r
X-Powered-By: PHP/5.3.15
Cache-Control: max-age=0, must-revalidate
Last-Modified: Mon, 16 Apr 2012 23:01:32 GMT
Content-Length: 16
Content-Type: text/html
X-Cache: MISS from localhost
Via: 1.1 localhost (squid/3.2.9)
Connection: keep-alive

localhost: ~ $ curl --silent -o /dev/null --dump-header /dev/stdout http://localhost:3128/test.php
HTTP/1.1 200 OK
X-Powered-By: PHP/5.3.15
Last-Modified: Mon, 16 Apr 2012 23:01:32 GMT
Content-Length: 16
Content-Type: text/html
Date: Wed, 17 Apr 2013 00:17:43 GMT
Server: Apache/2.2.22 (Unix) DAV/2 PHP/5.3.15 with Suhosin-Patch mod_ssl/2.2.22 OpenSSL/0.9.8r
Cache-Control: max-age=0, must-revalidate
Age: 0
X-Cache: HIT from localhost
Via: 1.1 localhost (squid/3.2.9)
Connection: keep-alive

localhost: ~ $ curl --silent -o /dev/null --dump-header /dev/stdout "http://localhost:3128/test.php?vary=1"
HTTP/1.1 200 OK
Date: Wed, 17 Apr 2013 00:17:58 GMT
Server: Apache/2.2.22 (Unix) DAV/2 PHP/5.3.15 with Suhosin-Patch mod_ssl/2.2.22 OpenSSL/0.9.8r
X-Powered-By: PHP/5.3.15
Cache-Control: max-age=0, must-revalidate
Last-Modified: Mon, 16 Apr 2012 23:01:32 GMT
Vary: Accept-Encoding
Content-Length: 16
Content-Type: text/html
X-Cache: MISS from localhost
Via: 1.1 localhost (squid/3.2.9)
Connection: keep-alive

localhost: ~ $ curl --silent -o /dev/null --dump-header /dev/stdout "http://localhost:3128/test.php?vary=1"
HTTP/1.1 200 OK
Date: Wed, 17 Apr 2013 00:18:00 GMT
Server: Apache/2.2.22 (Unix) DAV/2 PHP/5.3.15 with Suhosin-Patch mod_ssl/2.2.22 OpenSSL/0.9.8r
X-Powered-By: PHP/5.3.15
Cache-Control: max-age=0, must-revalidate
Last-Modified: Mon, 16 Apr 2012 23:01:32 GMT
Vary: Accept-Encoding
Content-Length: 16
Content-Type: text/html
X-Cache: MISS from localhost
Via: 1.1 localhost (squid/3.2.9)
Connection: keep-alive

答案1

不管怎样，我发现 3.3.4 版本也存在同样的问题，而且似乎这个帖子squid-users 中描述了 3.2.1 中存在的相同问题。我注意到它似乎可以与 3.1.10 配合使用（默认情况下，它随我的包管理器一起安装）。

通过分析日志，我能够确定存储期间（即初始请求）使用的哈希查找键与后续请求期间使用的哈希查找键不同。这就是后续查找缓存未命中的原因。

有了这些信息（额外的搜索条件），我能够找到此错误报告描述问题。该错误尚未解决。

希望这可以帮助！

答案2

这确实是一个错误，目前已修复，更多信息Squid 的错误追踪器。

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