Varnish¶

Description

Varnish is a caching front-end server. This document has notes on how to use Varnish with Plone.

Introduction ¶

This chapter contains information about using the Varnish caching proxy with Plone.

http://varnish-cache.org/

To use Varnish with Plone

Learn how to install and configure Varnish
Add Plone virtual hosting rule to the default varnish configuration

Installation ¶

You can install using packages (RPM/DEB) - consult your operating system instructions. This is the recommended method.
You can install backports
You can install using buildout

Backporting examples (Ubuntu 8.04 Hardy Heron)

http://www.lunix.com.au/blog/sane_varnish_on_hardy/

Buildout examples

http://pypi.python.org/pypi/plone.recipe.varnish

Management console ¶

Telnet console ¶

The telent management console is available on some configurations where varnishadm cannot be used. The functionality is the same.

Example:

ssh yourhost
# Your system does not have a secret handshake file
telnet localhost 6082

Note

Port number depends on your Varnish settings.

Quit console ¶

Quit command:

quit

Purging the cache ¶

This will remove all entries from the Varnish cache:

url.purge .*

Loading new VCL for the live varnish daemon ¶

More often than not, it is beneficial to load new configuration without bringing the cache down for maintenance. Using this method also checks the new VCL for syntax errors before activating it. Logging in to Varnish CLI requires the varnishadm tool, the address of the management interface, and the secret file for authentication.

See the varnishadm man-page for details.

Opening a new CLI connection to the Varnish console, in a buildout-based Varnish installation:

parts/varnish-build/bin/varnishadm -T localhost:8088

Port 8088 is defined in buildout.cfg:

[varnish-instance]
telnet = localhost:8088

Opening a new CLI connection to the Varnish console, in a system-wide Varnish installation on Ubuntu/Debian:

varnishadm -T localhost:6082 -S /etc/varnish/secret

You can dynamically load and parse a new VCL config file to memory:

vcl.load <name> <file>

For example:

vcl.load newconf_1 /etc/varnish/newconf.vcl

vcl.load will load and compile the new configuration. Compilation will fail and report on syntax errors. Now that the new configuration has been loaded, it can be activated with:

vcl.use newconf_1

Note

Varnish remembers <name> in vcl.load, so every time you need to reload your config you need to invent a new name for vcl.load / vcl.use command pair.

Logs ¶

To see a real-time log dump (in a system-wide Varnish configuration):

varnishlog

By default, Varnish does not log to any file and keeps the log only in memory. If you want to extract Apache-like logs from varnish, you need to use the varnishncsa utility.

Stats ¶

Check live "top-like" Varnish statistics:

parts/varnish-build/bin/varnishstat

Use the admin console to print stats for you:

stats
200 2114

       95717  Client connections accepted
      132889  Client requests received
       38638  Cache hits
       21261  Cache hits for pass
      ...

Varnish buildout restart snippet ¶

The following snippet will restart a varnishd instance which has been started from the plone.recipe.varnish buildout directly invoking bin/varnish-instance command.

It will also create an Apache-compatible log file which you can examine using text editing tools by running the varnishncsa command which will read log data from the Varnish memory-mapped file, and write it to a text file in Apache format.

Example:

#!/bin/sh
# Varnish restart script
sudo killall varnishd
sudo bin/varnish-instance
# Create Apache compatible log file
sudo kill `cat var/varnishncsa.pid`
sudo parts/varnish-build/bin/varnishncsa -D -d -a -w var/log/varnish.log -P var/varnishncsa.pid

Virtual hosting proxy rule ¶

When Varnish has been set-up you need to include Plone virtual hosting rule in its configuration file.

If you want to map Varnish backend directly to Plone-as-a-virtualhost (i.e. Zope's VirtualHostMonster is used to map site name to Plone site instance id) use req.url mutating.

The following maps the Plone site id plonecommunity to the plonecommunity.mobi domain. Plone is a single Zope instance, running on port 9999.

Example:

backend plonecommunity {
        .host = "127.0.0.1";
        .port = "9999";
}

sub vcl_recv {
        if (req.http.host ~ "^(www.)?plonecommunity.mobi(:[0-9]+)?$"
            || req.http.host ~ "^plonecommunity.mfabrik.com(:[0-9]+)?$") {

                set req.backend = plonecommunity
                set req.url = "/VirtualHostBase/http/" req.http.host ":80/plonecommunity/VirtualHostRoot" req.url;
                set req.backend = plonecommunity;
        }
}

Varnishd port and IP address to listen ¶

You give IP address(s) and ports to Varnish to listen to on the varnishd command line using -a switch. Edit /etc/default/varnish:

DAEMON_OPTS="-a 192.168.1.1:80 \
             -T localhost:6082 \
             -f /etc/varnish/default.vcl \
             -s file,/var/lib/varnish/$INSTANCE/varnish_storage.bin,1G"

Cached and editor subdomains ¶

You can provide an uncached version of the site for editors:

http://serverfault.com/questions/297541/varnish-cached-and-non-cached-subdomains/297547#297547

Varnish and I18N ¶

Please see cache issues related to LinguaPlone.

Sanitizing cookies ¶

Any cookie set on the server side (session cookie) or on the client-side (e.g. Google Analytics Javascript cookies) is poison for caching the anonymous visitor content.

HTTP caching needs to deal with both HTTP request and response cookie handling

HTTP request Cookie header. The browser sending HTTP request with Cookie header confuses Varnish cache look-up. This header can be set by Javascript also, not just by the server. Cookie can be preprocessed in vcl_recv.
HTTP response Set-Cookie header. This is server-side cookie set. If your server is setting cookies Varnish does not cache these responses by default. Howerver, this might be desirable behavior if e.g. multi-lingual content is served from one URL with language cookies. Set-Cookie can be post-processed in vcl_fetch.

Example how remove all Plone related cookies besides ones dealing with the logged in users (content authors):

sub vcl_recv {

  if (req.http.Cookie) {
      # (logged in user, status message - NO session storage or language cookie)
      set req.http.Cookie = ";" req.http.Cookie;
      set req.http.Cookie = regsuball(req.http.Cookie, "; +", ";");
      set req.http.Cookie = regsuball(req.http.Cookie, ";(statusmessages|__ac|_ZopeId|__cp)=", "; \1=");
      set req.http.Cookie = regsuball(req.http.Cookie, ";[^ ][^;]*", "");
      set req.http.Cookie = regsuball(req.http.Cookie, "^[; ]+|[; ]+$", "");

      if (req.http.Cookie == "") {
          remove req.http.Cookie;
      }
  }
  ...

# Let's not remove Set-Cookie header in VCL fetch
sub vcl_fetch {

    # Here we could unset cookies explicitly,
    # but we assume plone.app.caching extension does it jobs
    # and no extra cookies fall through for HTTP responses we'd like to cache
    # (like images)

    if (!beresp.cacheable) {
        return (pass);
    }
    if (beresp.http.Set-Cookie) {
        return (pass);
    }
    set beresp.prefetch =  -30s;
    return (deliver);
}

The snippet for stripping out non-Plone cookies comes from http://www.phase2technology.com/node/1218/

That article notes that "this processing occurs only between Varnish and the backend [...]; the client, typically a user’s browser, still has all the cookies. Nothing is happening to the client’s original request." While it's true that the browser still has the cookies, they never reach the backend and are therefor ignored.

Another example how to purge Google cookies only and allow other cookies by default:

sub vcl_recv {


         # Remove Google Analytics cookies - will prevent caching of anon content
         # when using GA Javascript. Also you will lose the information of
         # time spend on the site etc..
         if (req.http.cookie) {
            set req.http.Cookie = regsuball(req.http.Cookie, "__utm.=[^;]+(; )?", "");
            if (req.http.cookie ~ "^ *$") {
                remove req.http.cookie;
            }
          }

          ....

More info ¶

Do not cache error pages ¶

You can make sure that Varnish does not accidentally cache error pages. E.g. it would cache front page when the site is down:

sub vcl_fetch {
        if ( beresp.status >= 500 ) {
                set beresp.ttl = 0s;
                set beresp.cacheable = false;
        }
        ...
}

More info

https://www.varnish-cache.org/lists/pipermail/varnish-misc/2010-February/003774.html

Custom and full cache purges ¶

Below is an example how to create an action to purge the whole Varnish cache.

First you need to allow HTTP PURGE request in default.vcl from localhost. We'll create a special PURGE command which takes URLs to be purged out of the cache in a special header:

acl purge {
        "localhost";
        # XXX: Add your local computer public IP here if you
        # want to test the code against the production server
        # from the development instance
}

...

sub vcl_recv {

        ...

        # Allow PURGE requests clearing everything
        if (req.request == "PURGE") {
                if (!client.ip ~ purge) {
                        error 405 "Not allowed.";
                }
                # Purge for the current host using reg-ex from X-Purge-Regex header
                purge("req.http.host == " req.http.host " && req.url ~ " req.http.X-Purge-Regex);
                error 200 "Purged.";
        }
}

Then let's create a Plone view which will make a request from Plone to Varnish (upstream localhost:80) and issue PURGE command. We do this using Requests Python lib.

Example view code:

import requests

from Products.CMFCore.interfaces import ISiteRoot
from five import grok

from requests.models import Request

class Purge(grok.CodeView):
    """
    Purge upstream cache from all entries.

    This is ideal to hook up for admins e.g. through portal_actions menu.

    You can access it as admin::

        http://site.com/@@purge

    """

    grok.context(ISiteRoot)

    # Onlyl site admins can use this
    grok.require("cmf.ManagePortal")

    def render(self):
        """
        Call the parent cache using Requets Python library and issue PURGE command for all URLs.

        Pipe through the response as is.
        """

        # This is the root URL which will be purged
        # - you might want to have different value here if
        # your site has different URLs for manage and themed versions
        site_url = self.context.portal_url() + "/"

        headers = {
                   # Match all pages
                   "X-Purge-Regex" : ".*"
        }

        resp = requests.request("PURGE", site_url + "*", headers=headers)

        self.request.response["Content-type"] = "text/plain"
        text = []

        text.append("HTTP " + str(resp.status_code))

        # Dump response headers as is to the Plone user,
        # so he/she can diagnose the problem
        for key, value in resp.headers.items():
            text.append(str(key) + ": " + str(value))

        # Add payload message from the server (if any)

        if hasattr(resp, "body"):
                text.append(str(resp.body))

More info

Round robin balancing ¶

Varnish can do round robin load balancing internally. You want to distribute CPU intensive load between several ZEO front end client instances each listeting to its own port.

Example:

# Round-robin between two ZEO front end clients

backend app1 {
.host = "localhost";
.port = "8080";
}

backend app2 {
.host = "localhost";
.port = "8081";
}

director app_director round-robin {
  {
      .backend = app1;
  }
  {
      .backend = app2;
  }
}


sub vcl_recv {

 if (req.http.host ~ "(www\.|www2\.)?app\.fi(:[0-9]+)?$") {
    set req.url = "/VirtualHostBase/http/www.app.fi:80/app/app/VirtualHostRoot" req.url;
    set req.backend = app_director;
  }

Varnish¶

Introduction ¶

Installation ¶

Management console ¶

`varnishadm`¶

Telnet console ¶

Quit console ¶

Purging the cache ¶

Loading new VCL for the live varnish daemon ¶

Logs ¶

Stats ¶

Varnish buildout restart snippet ¶

Virtual hosting proxy rule ¶

Varnishd port and IP address to listen ¶

Cached and editor subdomains ¶

Varnish and I18N ¶

Sanitizing cookies ¶

More info ¶

Do not cache error pages ¶

Custom and full cache purges ¶

Round robin balancing ¶

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