Должны ли Varnish Hits касаться PHP?

У меня есть достаточно большой сайт Drupal, который находится в Varnish на коробке с 4 ГБ памяти. Я думал (надеялся? Предполагал?), Что установка Varnish перед Nginx / PHP-FPM снимет нагрузку с PHP, но PHP все еще кажется очень active, и я получаю больше предупреждений о том, что объем памяти увеличился более чем на 90%, чем я ожидал.

Я в корне неправильно понимаю, что делает Varnish? Я ожидал, что он будет кэшировать полный HTTP-ответ и просто выгнать его, если он был кэширован, и ни один запрос к Nginx, тем более PHP, никогда не будет выполнен, пока запрошенный URL-адрес находится в кеше. Тем не менее, разговаривая с людьми, которые, как мне кажется, будут знать по этой теме больше, чем я знаю, я получаю информацию, которая указывает на обратное.

Кто-нибудь может заполнить эти пробелы? Чего мне следует ожидать от Varnish в контексте сайта Drupal, где обширный большая часть трафика анонимна и поэтому подлежит кешированию Varnish?

ОБНОВИТЬ

По запросу вот мой конфиг (default.vcl - также в суть):

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 {
}