我在Apache/2.4.10服务器前面运行一个varnish-3.0.5实例。两者都在同一台Ubuntu 12.04.4机器上。Varnish服务器随机地将一些请求转发到后端服务器，即使它已经在缓存中有页面了。
当我做一个简单的请求时：
GET http://www.example.com/
Accept: */*
Accept-Encoding: gzip, deflate
Host: www.example.com
User-Agent: runscope/0.1
我有时会从缓存中收到正确的响应：
Accept-Ranges: bytes
Age: 5973
Cache-Control: private, no-cache, no-store, must-revalidate
Connection: keep-alive
Content-Encoding: gzip
Content-Length: 10015
Content-Type: text/html; charset=utf-8
Date: Fri, 24 Oct 2014 15:26:35 GMT
Expires: -1
Last-Modified: Fri, 24 Oct 2014 13:47:02 GMT
Server: Apache
Vary: Accept-Encoding
Via: 1.1 varnish
X-Varnish: 10531909 10507062
有时（更经常）直接来自Apache的响应：
Cache-Control: no-cache
Connection: keep-alive
Content-Encoding: gzip
Content-Length: 10015
Content-Type: text/html; charset=utf-8
Date: Fri, 24 Oct 2014 15:28:00 GMT
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Last-Modified: Fri, 24 Oct 2014 15:28:00 GMT
Server: Apache
Set-Cookie: [truncated]
Vary: Accept-Encoding
我确信该项仍在缓存中，因为在直接来自Apache的几次响应之后，我收到了来自Varnish的响应，其中Age标头包含的数字比Varnish上一次回答中的数字更高。
我的VCL文件：
# Default backend definition. Set this to point to your content server.
backend default {
.host = "127.0.0.1";
.port = "8080";
}
# List of IPs allowed to erase things from cache
acl purge {
"localhost";
"127.0.0.1"/8;
}
sub vcl_recv {
# Purge item from the cache
if (req.request == "PURGE") {
if (!client.ip ~ purge) {
error 405 "Not allowed.";
}
return (lookup);
}
# Setting Forwarding header
if (req.restarts == 0) {
if (req.http.x-forwarded-for) {
set req.http.X-Forwarded-For =
req.http.X-Forwarded-For + ", " + client.ip;
} else {
set req.http.X-Forwarded-For = client.ip;
}
}
## Pipeline ajax requests except of requests for [truncated]
if (req.http.X-Requested-With == "XMLHttpRequest" && req.url !~ "^/[truncated]") {
return(pipe);
}
if (req.request != "GET" &&
req.request != "HEAD" &&
req.request != "PUT" &&
req.request != "POST" &&
req.request != "TRACE" &&
req.request != "OPTIONS" &&
req.request != "DELETE") {
/* Non-RFC2616 or CONNECT which is weird. */
return (pipe);
}
if (req.request != "GET" && req.request != "HEAD") {
/* We only deal with GET and HEAD by default */
return (pass);
}
## Remove GCLID param from googles adds
set req.url = regsuball(req.url,"?gclid=[^&]+$",""); # strips when QS = "?gclid=AAA"
set req.url = regsuball(req.url,"?gclid=[^&]+&","?"); # strips when QS = "?gclid=AAA&foo=bar"
set req.url = regsuball(req.url,"&gclid=[^&]+",""); # strips when QS = "?foo=bar&gclid=AAA" or QS = "?foo=bar&gclid=AAA&bar=baz"
### always cache these items:
## JavaScript
if (req.request == "GET" && req.url ~ ".(js)") {
return (lookup);
}
## images
if (req.request == "GET" && req.url ~ ".(gif|jpg|jpeg|bmp|png|tiff|tif|ico|img|tga|wmf)$") {
return (lookup);
}
## various other content pages
if (req.request == "GET" && req.url ~ ".(css|html)$") {
return (lookup);
}
## multimedia
if (req.request == "GET" && req.url ~ ".(svg|swf|ico|mp3|mp4|m4a|ogg|mov|avi|wmv)$") {
return (lookup);
}
## xml
if (req.request == "GET" && req.url ~ ".(xml)$") {
return (lookup);
}
## Do not cache POST requests
if (req.request == "POST") {
return (pipe);
}
## Do not cache the [truncated]
if (req.url ~ "^/[truncated]") {
return (pipe);
}
## Cache the [truncated]
if (req.url ~ "^/[truncated]") {
return (lookup);
}
## Cache the [truncated]
if (req.url ~ "^/[truncated]") {
return (lookup);
}
## Do not cache the [truncated]
if (req.url ~ "^/[truncated]") {
return (pipe);
}
## Exceptions for [truncated]
if (req.url ~ "^/[truncated]") {
return (pass);
}
## Exceptions for [truncated]
if (req.url ~ "^/[truncated]") {
return (pipe);
}
return (lookup);
}
sub vcl_hash {
hash_data(req.url);
if (req.http.host) {
hash_data(req.http.host);
} else {
hash_data(server.ip);
}
## Make a request to check the logged in status of the current user
if (req.request == "GET" && req.url !~ ".(js|css|html|gif|jpg|jpeg|bmp|png|tiff|tif|ico|img|tga|wmf|svg|swf|ico|mp3|mp4|m4a|ogg|mov|avi|wmv|xml)$" && req.http.cookie ~ "cache-logged-in=1") {
hash_data("logged-in");
}
return (hash);
}
#
sub vcl_hit {
if (req.request == "PURGE") {
purge;
error 200 "Purged.";
}
return (deliver);
}
#
sub vcl_miss {
if (req.request == "PURGE") {
purge;
error 200 "Purged.";
}
return (fetch);
}
#
sub vcl_fetch {
## If the request to the backend returns a code other than 200, restart the loop
## If the number of restarts reaches the value of the parameter max_restarts,
## the request will be error'ed. max_restarts defaults to 4. This prevents
## an eternal loop in the event that, e.g., the object does not exist at all.
## this rule also allows for 301's and 302's redirects...
## Unset cookies sent from the backend if they are not necessary
if (req.url ~ "[truncated]")) {
if (beresp.http.set-cookie !~ "cache-logged-in") {
unset beresp.http.set-cookie;
}
}
if (beresp.status != 200 && beresp.status != 403 && beresp.status != 404 && beresp.status != 301 && beresp.status != 302 && beresp.status != 303) {
return (restart);
}
# if I cant connect to the backend, ill set the grace period to be 7200 seconds to hold onto content
set beresp.ttl = 7200s;
set beresp.grace = 7200s;
# If the header X-nocache is present, do not cache the item
if (beresp.http.x-nocache) {
return (hit_for_pass);
}
if (beresp.status == 404) {
set beresp.ttl = 0s;
}
if (beresp.status >= 500) {
set beresp.ttl = 0s;
}
if (req.request == "GET" && req.url ~ ".(gif|jpg|jpeg|bmp|png|tiff|tif|ico|img|tga|wmf)$") {
set beresp.ttl = 86400s;
}
else if (req.request == "GET" && req.url ~ ".(css|html)$") {
## various other content pages
set beresp.ttl = 86400s;
}
else if (req.request == "GET" && req.url ~ ".(js)$") {
set beresp.ttl = 86400s;
}
else if (req.request == "GET" && req.url ~ ".(xml)$") {
set beresp.ttl = 86400s;
}
else if (req.request == "GET" && req.url ~ ".(svg|swf|ico|mp3|mp4|m4a|ogg|mov|avi|wmv)$") {
## multimedia
set beresp.ttl = 86400s;
}
else {
set beresp.http.Expires = "-1";
set beresp.http.Cache-Control = "private, no-cache, no-store, must-revalidate";
}
return(deliver);
}
转发给apache的请求与清漆中的请求不同，这是简单的解释。至于它们的差异，有多种选项需要查看完整的请求，但可能包括：-cookie（请注意，apache请求正在设置cookie，所以我将从这里开始）。-url大小写的差异（您的hash区分大小写）。
在vcl_recv中取消设置req.http.cookie。