我有一个相当大的 Drupal 网站，使用 Varnish 安装在一个有 4GB 内存的机器上。我曾想过（希望？假设？）在 Nginx/PHP-FPM 前面放置 Varnish 可以减轻 PHP 的负担，但 PHP 似乎仍然非常活动，并且我收到比我预期更多的警告，即内存已攀升至 90% 以上。
我是否从根本上误解了 Varnish 的作用？我原本的预期是，它会缓存完整的 HTTP 响应，如果已缓存，则将其踢出，只要请求的 URL 在缓存中，就不会向 Nginx 发出任何请求，更不用说 PHP 了。然而，在与那些我认为比我更了解这个话题的人交谈时，我得到的信息却表明事实并非如此。
有人能填补这些空白吗？在 Drupal 站点的环境中，我应该对 Varnish 有什么期望？广阔的大多数流量是匿名的，因此会受到 Varnish 缓存的影响？
更新
根据要求，这是我的配置（default.vcl-也是要旨)：
backend default {
.host = "127.0.0.1";
.port = "8080";
}
acl purge {
# Add local/internal server IPs
"localhost";
"127.0.0.1";
}
sub vcl_recv {
if (req.http.User-Agent ~ "MS Search (5|6).0 Robot") {
error 403 "Forbidden";
}
if (req.http.User-Agent ~ "Microsoft-WebDAV-MiniRedir") {
error 403 "Forbidden";
}
remove req.http.ETAG;
remove req.http.X-Generator;
set req.grace = 30m;
if (req.url ~"apc.php") {
return (pass);
}
set req.http.host = regsuball(req.http.host, ":.*", "");
if (req.request == "PURGE") {
if (!client.ip ~ purge) {
error 405 "Not allowed.";
}
return(lookup);
}
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;
}
}
#--Add Server Status Exclusion
if (req.url ~ "/status") {
if (client.ip ~ purge) {
return(pass);
}
else {
error 750 "http://"+req.http.host;
}
}
#--Add Munin Exclusion
if (req.url ~ "munin") {
set req.backend = default;
set req.http.X-Cache = "Default-Pass";
return(pass);
}
# Handle compression correctly. Different browsers send different
# "Accept-Encoding" headers, even though they mostly all support the same
# compression mechanisms. By consolidating these compression headers into
# a consistent format, we can reduce the size of the cache and get more hits.=
# @see: http://varnish.projects.linpro.no/wiki/FAQ/Compression
# Properly handle different encoding types
if (req.http.Accept-Encoding) {
if (req.url ~ "(?i)\.(bmp|bz2|gif|gz|ico|img|jpeg|jpg|lzma|mp3|ogg|png|swf|tbz|tga|tgz|wmf|zip)(\?.*|)$") {
remove req.http.Accept-Encoding;
}
else if (req.http.Accept-Encoding ~ "gzip") {
set req.http.Accept-Encoding = "gzip";
}
else if (req.http.Accept-Encoding ~ "deflate") {
set req.http.Accept-Encoding = "deflate";
}
else {
remove req.http.Accept-Encoding;
}
}
if ( req.restarts > 0
&& req.url ~ "(?i)\.(bmp|bz2|css|gif|gz|ico|img|jpeg|jpg|js|lzma|mp3|ogg|png|swf|tbz|tga|tgz|txt|wmf|zip)(\?.*|)$"
) {
return(lookup);
}
if ( req.restarts > 0
|| req.http.Content-Type ~ "multipart/form-data"
|| req.http.X-Requested-With == "XMLHttpRequest" #dont cache ajax requests
|| req.url ~ "nocache"
#|| req.request == "POST" #never cache POST requests
|| req.url ~ "/(delete|add|edit|update)|render=media" #--Dont intercept "itok=" #-- || req.url ~ "itok="
|| ( req.http.Referer ~ "/(delete|add|edit|update)" )
|| req.url ~ "/(upload/profileimage|upload/bannerimage|docbldr/api/uploadimage2|db/item/save)"
|| req.http.Referer ~ "/(upload/profileimage|upload/bannerimage|docbldr/api/uploadimage2|db/item/save)"
) {
return(pass);
}
# Allow the backend to serve up stale content if it is responding slowly.
# Do not cache these paths.
if (req.url ~ "^/status\.php$" ||
req.url ~ "^/update\.php$" ||
req.url ~ "^/ooyala/ping$" ||
req.url ~ "^/admin/build/features" ||
req.url ~ "^/info/.*$" ||
req.url ~ "^/flag/.*$" ||
req.url ~ "^.*/ajax/.*$" ||
req.url ~ "^.*/ahah/.*$"
) {
return (pass);
}
# Do not allow outside access to cron.php or install.php.
if (req.url ~ "^/(cron|install)\.php$" && !client.ip ~ purge) {
error 404 "Page not found.";
}
#--If POST requests don't include file uploads and the master is being overwhelmed by POSTS, uncomment below and comment out the POST line above
if ( req.request == "POST" #never cache POST requests
|| req.url ~ "(admin|login)"
) {
return(pass);
}
## always cache these images & static assets
## MUST OCCUR AFTER "req.restart" CHECK ABOVE!
if (req.request ~ "GET|HEAD" && (req.url ~ "(?i)\.(bmp|bz2|css|gif|gz|ico|img|jpeg|jpg|js|lzma|mp3|ogg|png|swf|tbz|tga|tgz|txt|wmf|zip)(\?.*|)$"
)) {
remove req.http.cookie;
return(lookup);
}
### don't cache authenticated sessions
if (req.http.Cookie && req.http.Cookie ~ "(PHPSESSID|^SESS)") {
return(pass);
}
# DO cache this ajax request. # WordPress
if(req.http.X-Requested-With == "XMLHttpRequest" && req.url ~ "recent_reviews") {
return (lookup);
}
# Remove all cookies that Drupal doesn't need to know about. ANY remaining
# cookie will cause the request to pass-through to Apache. For the most part
# we always set the NO_CACHE cookie after any POST request, disabling the
# Varnish cache temporarily. The session cookie allows all authenticated users
# to pass through as long as they're logged in.
if (req.http.Cookie) {
set req.http.Cookie = ";" + req.http.Cookie;
set req.http.Cookie = regsuball(req.http.Cookie, "; +", ";");
set req.http.Cookie = regsuball(req.http.Cookie, ";(SESS[a-z0-9]+|NO_CACHE)=", "; \1=");
set req.http.Cookie = regsuball(req.http.Cookie, ";[^ ][^;]*", "");
set req.http.Cookie = regsuball(req.http.Cookie, "^[; ]+|[; ]+$", "");
if (req.http.Cookie == "") {
unset req.http.Cookie;
return(lookup);
}
else {
return (pass);
}
}
return (lookup);
}
sub vcl_hit {
if (req.request == "PURGE") {
purge;
error 200 "Purged.";
}
}
sub vcl_miss {
if (req.request == "PURGE") {
error 404 "Not in cache.";
}
if (req.url ~ "(?i)\.(bmp|bz2|css|gif|gz|ico|img|jpeg|jpg|js|lzma|mp3|ogg|png|swf|tbz|tga|tgz|txt|wmf|zip)(\?.*|)$") {
unset req.http.cookie;
set req.url = regsub(req.url, "\?.*", "");
}
}
sub vcl_hash {
hash_data(req.url);
if (req.http.host) {
hash_data(req.http.host);
} else {
hash_data(server.ip);
}
if (req.http.x-forwarded-proto) {
hash_data(req.http.x-forwarded-proto);
}
return (hash);
}
sub vcl_fetch {
set beresp.grace = 30m;
remove beresp.http.ETAG;
remove beresp.http.X-Generator;
remove beresp.http.Link;
remove beresp.http.Server;
if (beresp.status == 404 && req.restarts == 0) {
return(restart);
}
# Keep static content in Browser Cache and Varnish Cache for a while. Tweak as needed.
if (req.url ~ "(?i)\.(bmp|bz2|css|gif|gz|ico|img|jpeg|jpg|js|lzma|mp3|ogg|png|swf|tbz|tga|tgz|txt|wmf|zip)(\?.*|)$") {
#-- Prevent Varnish from caching unsuccessful static requests
if (beresp.status != 200 && req.restarts == 0) {
return(restart);
}
unset beresp.http.set-cookie;
set beresp.http.cache-control = "max-age=3600; public";
set beresp.ttl = 1800s;
}
set beresp.http.X-Host = req.http.host;
set beresp.http.X-URL = req.url;
# make Varnish compress content before storing it in cache and store text content for a while.
if (beresp.http.content-type ~ "text") {
set beresp.ttl = 1800s;
set beresp.do_gzip = true;
}
}
sub vcl_error {
# Redirect to some other URL in the case of a homepage failure.
if (obj.status == 750) {
set obj.http.Location = obj.response;
set obj.status = 302;
return(deliver);
}
# Otherwise redirect to the homepage, which will likely be in the cache.
set obj.http.Content-Type = "text/html; charset=utf-8";
synthetic {"
<html>
<head>
<title>Page Unavailable</title>
<style>
body { background: #303030; text-align: center; color: white; }
#page { border: 1px solid #CCC; width: 500px; margin: 100px auto 0; padding: 30px; background: #323232; }
a, a:link, a:visited { color: #CCC; }
.error { color: #FFF;font-size:24px;padding:15px; }
</style>
</head>
<body onload="setTimeout(function() { window.location = '"} + req.url + {"' }, 5000)">
<div id="page">
<h1 class="title">Page Unavailable</h1>
<p>The page you requested is temporarily unavailable.</p>
<p>We'll try again in 5 seconds.</p>
<div class="error">(Error "} + obj.status + " " + obj.response + {")</div>
</div>
</body>
</html>
"};
return (deliver);
}
sub vcl_deliver {
}
答案1
这实际上取决于你的网站是如何设置的。如果出现以下情况，Varnish 不会缓存页面：
- 它包含身份验证标头
- 它包含 cookie 标头
- 仅缓存 GET 和 HEAD 请求
- 缓存的最小 TTL 为 120 秒，因此你可能需要增加该值
如果您正在使用 PHP 会话，那么您可能会遇到第二点。
我不知道 PHP 本身是否默认发送缓存控制标头，但也许如果你使用某些框架，这会自动完成。
实现诸如图像之类的内容的缓存非常容易（只要它们位于恒定路径下），但诸如 PHP 生成的页面之类的动态内容在实现方面可能需要多加考虑。
编辑：剪掉我看到你的配置中有与 APC 相关的代码，所以放弃实现 PHP 加速器的建议吧！
修改 2：好吧，现在想起来，我的回答有点短。使用 varnishncsa 将帮助您查看哪些页面命中或丢失，因此请尝试运行以下命令：
varnishncsa -f -m 'TxHeader:X-Cache: MISS'
-m 开关与运行 varnishlog 时为每个事务标记的标签相同（按其编号分组）。
其他有用的命令可以帮助您的是 varnishstat（统计，显示命中率百分比），varnishtop（显示所有请求中的顶级标签）和 varnishhist（从客户端接收到服务器接收的事务直方图[来自内存]，管道字符是缓存命中，哈希字符是缓存未命中，尺度是对数，1-e0 为 1 秒）。