Make Your Websites Fly!

Come Fly With Me

Presenter Notes

What is Reverse Proxy?

Reverse Proxy

While a forward proxy is usually situated between the client application (such as a web browser) and the server(s) hosting the desired resources, a reverse proxy is usually situated closer to the server(s) and will only return a configured set of resources.

http://en.wikipedia.org/wiki/Reverse_proxy

Presenter Notes

Varnish Cache

Come Fly With Me

Presenter Notes

Varnish Makes Websites Fly

We love Varnish because it's

built from the ground up as a reverse proxy
64bit, and blindingly fast
focused exclusively on HTTP
full of programmable behaviours
open source & commercially supported

Varnish Community https://www.varnish-cache.org/

Presenter Notes

Come Fly With Me

Facebook uses Varnish to serve billions of requests every day to users around the world.

David Recordon, Head of open source initiatives, Facebook.

Presenter Notes

"Facebook uses Varnish to serve billions of requests every day to users around the world. We like its simple architecture, which is designed for modern operating systems and find that it does not consume much CPU while handling heavy loads. Varnish is our favored HTTP cache and we use it heavily; whenever you load photos and profile pictures of your friends on Facebook, there's a very good chance that Varnish is involved."

David Recordon, Head of open source initiatives, Facebook.

Varnish Running On

Google top 1000 list:
 16 www.twitter.com (search.twitter.com)
 49 www.weather.com (www.weather.com)     
 53 www.answers.com (www.answers.com) 
 80 www.globo.com (www.globo.com)         
116 www.nytimes.com (or so they tell themselves)
160 www.slideshare.net (www.slideshare.net)      
186 www.livejournal.com (www.livejournal.com)  
etc

Global Alexa toolbar users:
(Note that facebook (#2) is using varnish, but this is not automatically discovered
  9 twitter.com (search.twitter.com)
 76 livejournal.com     
 95 weather.com     
111 globo.com         
112 stumbleupon.com
144 answers.com      
203 wikia.com            
220 squidoo.com 
etc

Varnish usage stats as at 2011-06-15

Presenter Notes

Google top 1000 list: Place 16 Varnish running on www.twitter.com (search.twitter.com) Place 49 Varnish running on www.weather.com (www.weather.com)
Place 53 Varnish running on www.answers.com (www.answers.com)
Place 80 Varnish running on www.globo.com (www.globo.com)
Place 116 Varnish running on www.nytimes.com (or so they tell themselves) Place 160 Varnish running on www.slideshare.net (www.slideshare.net)
Place 186 Varnish running on www.livejournal.com (www.livejournal.com)
Place 208 Varnish running on www.mercadolivre.com.br (www.mercadolivre.com.br) Place 215 Varnish running on www.y8.com (www.y8.com)
Place 313 Varnish running on www.robtex.com (www.robtex.com)
Place 368 Varnish running on www.manta.com (www.manta.com)
Place 370 Varnish running on www.squidoo.com (www.squidoo.com)
Place 403 Varnish running on www.taleo.net (www.taleo.net)
Place 488 Varnish running on www.gazeta.pl (www.gazeta.pl)
Place 564 Varnish running on www.wetter.com (www.wetter.com)
Place 579 Varnish running on www.spiegel.de (www.spiegel.de)
Place 596 Varnish running on www.merriam-webster.com (www.merriam-webster.com) Place 603 Varnish running on www.wat.tv (www.wat.tv)
Place 614 Varnish running on www.rutube.ru (www.rutube.ru)
Place 619 Varnish running on www.mercadolibre.com.mx (www.mercadolibre.com.mx) Place 652 Varnish running on www.zappos.com (www.zappos.com)
Place 693 Varnish running on www.xpg.com.br (www.xpg.com.br)
Place 700 Varnish running on www.espncricinfo.com (www.espncricinfo.com) Place 722 Varnish running on www.stumbleupon.com (www.stumbleupon.com)
Place 739 Varnish running on www.wwe.com (www.wwe.com)
Place 766 Varnish running on www.kapook.com (www.kapook.com)
Place 795 Varnish running on www.mercadolibre.com.ar (www.mercadolibre.com.ar) Place 870 Varnish running on www.xywy.com (www.xywy.com)
Place 885 Varnish running on www.break.com (www.break.com)
Place 969 Varnish running on www.mobifiesta.com (www.mobifiesta.com)
Place 987 Varnish running on www.mercadolibre.com (www.mercadolibre.com) Place 991 Varnish running on www.popcap.com (www.popcap.com)

Global Alexa toolbar users: (Note that facebook (#2) is using varnish, but this is not automatically discovered Place 9 Varnish running on twitter.com (search.twitter.com) Place 76 Varnish running on livejournal.com
Place 95 Varnish running on weather.com
Place 111 Varnish running on globo.com
Place 112 Varnish running on stumbleupon.com Place 144 Varnish running on answers.com
Place 203 Varnish running on wikia.com
Place 220 Varnish running on squidoo.com
Place 241 Varnish running on espncricinfo.com Place 251 Varnish running on slideshare.net Place 373 Varnish running on soundcloud.com
Place 389 Varnish running on drupal.org
Place 392 Varnish running on mercadolivre.com.br Place 403 Varnish running on businessinsider.com Place 435 Varnish running on forbes.com
Place 441 Varnish running on gazeta.pl
Place 479 Varnish running on posterous.com

Getting Started with Varnish

Download & Install

Use your standard package manager (HomeBrew, AppGet, etc). You'll need CYGWIN for Windows (sucks to be you :(

Point Varnish at your web site

# Simple .VCL file
backend default {
    .host = "varnish.local";
    .port = "80";
}

The default varnish configuration is automatically appended to yours.

Default varnish installation serves cached content from port 6081 proxied from 127.0.0.1:80.

Fire up the service

varnishd -f /usr/local/etc/varnish/default.vcl -s malloc,1G -a 0.0.0.0:8080

-T telnet listen address/port, -s storage, -a varnish address/port

Presenter Notes

Simple CFML Page

<CFHEADER NAME="Cache-Control" VALUE="s-maxage=600">

<cfoutput>
<html>
    <body>
        <h1>Hello cruel world!</h1>

        <strong>Generated by server:</strong> 
        #dateformat(now(),'ddd, mmm d yyyy')# #timeformat(now(),'HH:mm:ss')#<br>

        <strong>Loaded by browser:</strong> 
        <script type="text/javascript">document.write(new Date());</script>
    </body>
</html>
</cfoutput>

Shows the server time (affected by the cache) and the client time on the browser.

CFHEADER to send caching instructions; must use s-maxage (seconds)
No Cookies! Sessions should be disabled; by default varnish will invalidate caches if cookies are present

Don't worry you can have your cookies back later!

Presenter Notes

The Nature of Cookies

COOKIES!!! UMM-NUM-NUM-NUM-NUM!!!

Cookie Monster, CEO, No More Cookies Inc.

Cookie Monster

Presenter Notes

Varnish VCL

Come Fly With Me

Presenter Notes

How Varnish Works

8 subroutines control how Varnish behaves:

vcl_recv() Called after a request is received from the browser, but before it is processed.

vcl_pipe() Called when a request must be forwarded directly to the backend with minimal handling by Varnish (think HTTP CONNECT)

vcl_hash() Called to determine the hash key used to look up a request in the cache.

vcl_hit() Called after a cache lookup when the object requested has been found in the cache.

vcl_miss() Called after a cache lookup when the object requested was not found in the cache.

vcl_pass() Called when the request is to be passed to the backend without looking it up in the cache.

vcl_fetch() Called when the request has been sent to the backend and a response has been received from the backend.

vcl_deliver() Called before a response object (from the cache or the web server) is sent to the requesting client.

But really it boils down to just `vcl_recv()` and `vcl_fetch()`.

Presenter Notes

"The principal configuration mechanism is VCL (Varnish Configuration Language), a domain-specific language (DSL) used to write hooks which are called at critical points in the handling of each request. Most policy decisions are left to VCL code, making Varnish far more configurable and adaptable than most other HTTP accelerators. When a VCL script is loaded, it is translated to C, compiled to a shared object by the system compiler, and linked directly into the accelerator." Wikipedia: Varnish Cache

VCL_RECV

Processing Client Request

sub vcl_recv {
    # Remove user agent
    if (req.http.User-Agent) {
        set req.http.User-Agent = "";
    }
    # remove any cookies from client request
    unset req.http.cookie;
    # look up the cache
    return(lookup);
}

Modify Inbound Request from a Browser

tidy up the request; simplify the headers etc
get rid of cookies; but not always!
normalise the User-Agent; otherwise a cache per agent
look up the cache or; let them through

Presenter Notes

VCL_FETCH

Grabbing the Content Off Your Website

sub vcl_fetch {
  # cache period (ttl: time to live)
  set beresp.ttl = 45s;
  # cache grace period; serve dirty
  set beresp.grace = 15s;
}

How to Fetch Content

finding the backend
manage the cache timeout
getting dirty ;)
handling slow or unresponsive servers

Presenter Notes

Varnish Configuration

vcl_recv & vcl_fetch

# simple.vcl
backend default {
    .host = "varnish.local";
    .port = "80";
}

sub vcl_recv {
    # Remove user agent
    if (req.http.User-Agent) {
        set req.http.User-Agent = "";
    }
    # remove any cookies from client request
    unset req.http.cookie;
    # look up the cache
    return(lookup);
}

sub vcl_fetch {
  # cache period (ttl: time to live)
  set beresp.ttl = 45s;
  # cache grace period; serve dirty
  set beresp.grace = 15s;
}

Presenter Notes

Caching Strategies

Come Fly With Me

Presenter Notes

Caching Static Assets

Dealing with non-programmable things

sub vcl_recv {
    if (req.url ~ "\.(jpg|jpeg|gif|png|ico|css|zip|pdf|txt|tar|wav|bmp|rtf|js|flv|swf|html|htm)$") {
        unset req.http.Accept-Encoding;
        // Remove user agent
        if (req.http.User-Agent) {
            set req.http.User-Agent = "";
        }
        unset req.http.Cookie;
        return(lookup);
    }
}

~ is a regex operator for strings, set and unset update and remove a property, req.http properties are request headers, return(lookup) returns control to varnish, requesting a cache lookup if possible.

Apache Config: ./virtuals/mysite.conf

<VirtualHost *:80>
    # Set up caching on media files for 1 year (forever?)
    <FilesMatch "\.(jpg|jpeg|gif|png|ico|css|zip|pdf|txt|tar|wav|bmp|rtf|js|flv|swf|html|htm)$">
        ExpiresDefault A29030400
        Header append Cache-Control "public"
    </FilesMatch>
</VirtualHost>

Presenter Notes

This configuration leaves control of cache timeouts with Apache, but you can force a cache timeout in varnish with a line like "set beresp.ttl = 48h;"

Flush Varnish Cache

# IPs/domains that can access the purge url
acl purge {
    "localhost";
    "203.26.11.39";
}
sub vcl_recv {
    # Purge everything url - this isn't the squid way, but works
    if (req.url ~ "^/varnishpurge") {
       if (!client.ip ~ purge) {
            error 405 "Not allowed.";
       }
       if (req.url == "/varnishpurge") {
            ban("req.http.host == " + req.http.host + " && req.url ~ ^/");
            error 841 "Purged site.";
       }
       else {
            ban("req.http.host == " + req.http.host + " && req.url 
            \ ~ ^" + regsub( req.url, "^/varnishpurge(.*)$", "\1" ) + "$" );
            error 842 "Purged page.";
       }
    }
}

Use an ACL to restrict access to the sensitive functionality like flushing. For ACLs, the ~ operator is an 'in' check.

Presenter Notes

Flush Cache URLs

For example, flushing the entire site

http://www.fullasagoog.com/varnishpurge

For example, flushing a specific URL

http://www.fullasagoog.com/varnishpurge/blog/daemonite

Can be used as a hook to manage the cache from your upstream server. Allows administrators to flush problem pages on demand easily.

Presenter Notes

ban is for varnish 3 what purge was for 2. Bans are stored in memory, and every page request is checked against every ban - there are performance implications.

CTRL F5 to Force Cache Flush

acl CTRLF5 {
   "192.168.100.100";
}

sub vcl_hit {

  if (client.ip ~ CTRLF5) {
    if (req.http.pragma ~ "no-cache" || req.http.Cache-Control ~ "no-cache")
    {
      set obj.ttl = 0s;
      return(pass);
    }
    else { return(deliver); }
  }
  else { return(deliver); }
}

Hat Tip Dr Carter Blog

Allow administrators to easily flush the cache from their browser

Presenter Notes

Invalidate cache from client side

# IPs/domains that bypass cache
acl bypass {
    "1.2.3.4";
}

sub vcl_recv {
    if (client.ip ~ bypass) {
        return(pass);
    }
}

return(pass) passes the request through to the backend, bypassing the cache.

Useful if you want content contributors to see "live" content all the time.

Presenter Notes

Bypass Cache for a Cookie

sub vcl_recv {
    if (req.http.Cookie ~ "LOGGED-IN=1") {
        return(pass)
    }
}

Bypasses cache if there is a LOGGED-IN cookie with value 1.

Caches everything for anonymous users but gives a pass to authenticated users.

Presenter Notes

Punch through Cache with Header

sub vcl_recv {
    if (req.http.X-Requested-With == "XMLHttpRequest") {
        return(pass)
    }
}

ajax requests bypass cache. Keep everything static except personlised regions that are ajaxed into place.

Make sure you Javascript implementation for AJAX actually sets XMLHttpRequest :)

Presenter Notes

Normalising Headers

Varnish can include the user-agent and accept-encoding headers in cache hash, so normalising them is a good idea:

sub vcl_recv {
    if (req.http.Accept-Encoding) {
        if (req.http.Accept-Encoding ~ "gzip") {
            # if the browser supports it, we'll use gzip
            set req.http.Accept-Encoding = "gzip";
        } elsif (req.http.Accept-Encoding ~ "deflate") {
            # next, try deflate if it is supported
            set req.http.Accept-Encoding = "deflate";
        } else {
            # unknown algorithm. Probably junk, remove it
            unset req.http.Accept-Encoding;
        }
    }

    # Remove user agent
    if (req.http.User-Agent) {
        set req.http.User-Agent = "";
    }
}

Presenter Notes

Dishing Up Mobile

If your website serves different HTML to mobile users, you might use code like this:

if (req.http.User-Agent ~ "iP(hone|od)" || req.http.User-Agent ~ "Android" || 
\ req.http.User-Agent ~ "Symbian" || req.http.User-Agent ~ "^BlackBerry" || 
\ req.http.User-Agent ~ "^SonyEricsson" || req.http.User-Agent ~ "^Nokia" || 
\ req.http.User-Agent ~ "^SAMSUNG" || req.http.User-Agent ~ "^LG" || 
\ req.http.User-Agent ~ " webOS") {
    set req.http.User-Agent = "mobile";
}
else {
    set req.http.User-Agent = "desktop";
}

Presenter Notes

Custom Cache Hash

For example, caching by user role

sub vcl_hash {
    # these 2 entries are the default ones used for vcl. Below we add our own.
    set req.hash += req.http.host;
    set req.hash += req.url;

    set req.http.X-Varnish-Hashed-By = req.http.host req.url;

    if (req.http.Cookie ~ "ROLES") {
       set req.hash += regsub( req.http.Cookie, "^.*?ROLES=([^;]*);*.*$", "\1" );
       set req.http.X-Varnish-Hashed-By = req.http.X-Varnish-Hashed-By regsub( req.http.Cookie, "^.*?ROLES=([^;]*);*.*$", "\1" );
    }

    return(hash);
}

Adds a cookie ROLES to the cache key. req.http.X-Varnish-Hashed-By adds a helpful header for debugging.

Presenter Notes

Pass Original IP

Pass along original IP address as a custom header

sub vcl_recv {
    // Pass along the IP for uncached pages
    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;
    }
}

Great when you are doing something like Geo-Blocking on the server.

Presenter Notes

Varnish in the Wild

Come Fly With Me

Presenter Notes

AdNews: www.adnews.com.au

// vcl_fetch()
// Let any non "GET" / "HEAD" right through
if (req.request != "GET" && req.request != "HEAD"){
    set beresp.http.X-Cacheable = "NO:Not GET or HEAD";
    return(pass);
}
// strip cookies for everything except specific pages
elsif ( req.url ~ "profile" || req.url ~ "Login" || req.url ~ "login" || req.url ~ "logout" ) {
    set beresp.http.X-Cacheable = "NO:Login or logout page";
    return(pass);
}
else {
    unset beresp.http.set-cookie;
}

Dealing with comment forms, secure content & newsletter driven rushes on the site

pass form posts (ie not GET) and AJAX traffic (ie not HEAD)
pass member session pods for login/logout
cache everything else

Presenter Notes

Bomb Proof: fullasagoog.com

sub vcl_recv {
    set req.grace = 300s;
}
sub vcl_fetch {
    if (beresp.status == 500) {
        set beresp.saintmode = 20s;
        if (req.request != "POST") {
           return(restart);
        } else {
           error 500 "Failed";
        }
        set beresp.ttl = 5s;
    }
    set beresp.grace = 300s;
}

req.grace defines how old a cache can be if there is a backend problem
beresp.saintmode flags the current page on the current back end as "bad"
return(restart) to retry the request; if there is no "good" backend for the page, the grace will kick in
POST information can't really be restarted
beresp.grace is effectively the maximum grace the request can have
beresp.ttl is the cache timeout - setting it overrides the value in the Cache-Control header

Presenter Notes

Misbehaving Servers

Grace mode

When several clients are requesting the same page Varnish will send one request to the backend and place the others on hold while fetching one copy from the back end. In some products this is called request coalescing and Varnish does this automatically.

Saint mode

Sometimes servers get flaky. They start throwing out random errors. You can instruct Varnish to try to handle this in a more-than-graceful way - enter Saint mode. Saint mode enables you to discard a certain page from one backend server and either try another server or serve stale content from cache.

God mode

IDDQD

Presenter Notes

Tuning Varnish

Come Fly With Me

Presenter Notes

Varnish Tools

#show a histogram of hits (|) and misses (#) by the request time
varnishhist

#show the misses by most frequent
varnishtop -b -i txurl

#show general stats (e.g. proportion of hits to misses over time)
varnishstat

#live varnish logs (this is VERY verbose)
varnishlog

#varnish logs, grouped by request, for the daemon office IP
varnishlog -c -o SessionOpen 203.26.11.39

#live varnish logs in apache/NCSA "combined" log format
varnishncsa

Presenter Notes

varnishhist

Varnish History Graph

Presenter Notes

varnishtop -b -i txurl

 8.89 TxURL          /registered-user/displayTypeLoginPod/ajaxmode/1
 7.99 TxURL          /post/rss
 5.62 TxURL          /favicon.ico
 4.95 TxURL          /xml/ColdFusionMX.xml
 4.17 TxURL          /googblogpost/rss?format=xml
 3.94 TxURL          /googblogpost/rss
 3.74 TxURL          /xml/fullasagoog50.xml
 3.71 TxURL          /
 3.57 TxURL          /F15D6000-0A77-11E1-ACA5005056A301A8/redirect
 3.53 TxURL          /xml/export.xml
 3.47 TxURL          /8D5BD510-0A76-11E1-ACA5005056A301A8/redirect
 3.43 TxURL          /xml/FlashMX.xml
 3.35 TxURL          /index.cfm?objectID=08579C9F-C085-7808-85EB3D1CD6488792&flushcache=1
 3.11 TxURL          /cache/webskinAjaxLoader--0-D41D8CD98F00B204E9800998ECF8427E-D41D8CD98F00B204E9800998ECF8427E-313CA0907DADE6EA6215AA16A0685740.js
 3.11 TxURL          /cache/fcga--1311305428809-2FC28720EE6EF54DA2F5353760DAEA80-D41D8CD98F00B204E9800998ECF8427E-D41D8CD98F00B204E9800998ECF8427E.js
 3.11 TxURL          /cache/jquery--1305519744181-AA09F36EDAB33BAEF6A415F165FE5657-D41D8CD98F00B204E9800998ECF8427E-4CD1C3C5B197FB174E1BC7C9641A5874.js
 3.09 TxURL          /lib/tnw_pr

Shows cache misses by most frequent. Review this periodically for a sanity check on what's not getting cached.

Presenter Notes

Fully Sick & Radical Stuff

Come Fly With Me

Presenter Notes

Backend Mashups

https://www.varnish-cache.org/docs/trunk/tutorial/advanced_backend_servers.html

Map different server content into a single URL. Introduce a PHP application into your CFML web site. Imagine we hack the thing onto port 8000. Now, Varnish magic:

backend default {
    .host = "127.0.0.1";
    .port = "80";
}
backend php {
    .host = "127.0.0.1";
    .port = "8000";
}

Mash it up in vcl_recv

sub vcl_recv {
    if (req.url ~ "^/forums/") {
        set req.backend = php;
    } else {
        set req.backend = default.
    }
}

Mobile devices from a different backend? No problem.

if (req.User-agent ~ /mobile/)

Presenter Notes

Totally arbitrary data -- it's awesome.

Load Balancing

https://www.varnish-cache.org/docs/trunk/tutorial/advanced_backend_servers.html

Group several backend into a group of backends, aka directors. You can define several backends and group them together in a director.

backend server1 {
    .host = "192.168.0.10";
}
backend server2{
    .host = "192.168.0.10";
}

Now we create the director.:

director example_director round-robin {
    { .backend = server1; }
    { .backend = server2; }
}

round-robin director; distributes the incoming requests on a round-robin basis. random director; distributes requests randomly.

Presenter Notes

But what if one of your servers goes down? Can Varnish direct all the requests to the healthy server? Sure it can. This is where the Health Checks come into play.

Health checks, backend probes

Fail over for unhealthy servers

backend server1 {
    .host = "server1.example.com";
    .probe = {
        .url = "/";
        .interval = 5s;
        .timeout = 1s;
        .window = 5;
        .threshold = 3;
    }
}
backend server2 {
    .host = "server2.example.com";
    .probe = {
        .url = "/";
        .interval = 5s;
        .timeout = 1s;
        .window = 5;
        .threshold = 3;
    }
}

Seriously.

Presenter Notes

url What URL should varnish request.

interval How often should we poll

timeout What is the timeout of the probe

window Varnish will maintain a sliding window of the results. Here the window has five checks.

threshold How many of the .window last polls must be good for the backend to be declared healthy.

initial How many of the of the probes a good when Varnish starts - defaults to the same amount as the threshold.

Edge Side Includes (ESI)

Roughly speaking, ESI consists of three parts, of which Varnish so far, implements only one:

<esi:include>, <esi:remove> and  (implemented)
Content substitution based on variables and cookies (not yet)
Caching policy control (not relevant)

<esi:include> is to web content what <cfinclude> is to CFML

You can have recursive <esi:include> constructs, but their depth is limited by the parameter max_esi_includes defaulting to 5.
You can have any number of <esi:include> instructions in one document.
At the moment, only the src-Attribute is supported, alt and onerror are silently ignored.

Presenter Notes

ESI Standard (Varnish only supports a sub-set)

ESI element tags are inserted into HTML or other text based content during creation. Instead of being displayed to viewers these ESI tags are directives that instruct an ESI processor to take some action. The XML based ESI tags indicate to the edge-side processing agent the action that needs to be taken to complete the page's assembly. One simple example of an ESI element is the include tag which is used to include content external to the page. An ESI include tag placed in-line within an HTML document would look like this:

In this case the ESI processor would retrieve the src URL, or failing that the alt URL, or if that failed do nothing. The ESI system is usually a caching proxy server so it may have a local copy of these files which it can insert without going back to the server. Alternatively the whole page with the ESI tags may be cached, and only the ESI requests may be made to the origin server. This allows different caching times for different parts of the page, or different degrees of personalisation.

Wikipedia: ESI

Using ESIs

Embed ESI tags in your HTML output

<HTML>
<BODY>
Latest news: <esi:include src="/hotnews.cfm"/>
</BODY>
</HTML>

Activate ESI processing in your VCL

sub vcl_fetch {
    if (req.url == "/test.html") {
       set beresp.do_esi = true; /* Do ESI processing               */
       set beresp.ttl = 24 h;    /* Sets the TTL on the HTML above  */
    } elseif (req.url == "/hotnews.cfm") {
       set beresp.ttl = 1m;      /* Sets a one minute TTL on        */
                                 /*  the included object            */
    }
}

Presenter Notes

Example: esi remove The remove keyword allows you to remove output. You can use this to make a fall back of sorts, when ESI is not available, like this::

www.example.com

Example: This is a special construct to allow HTML marked up with ESI to render without processing. ESI Processors will remove the start ("") when the page is processed, while still processing the contents. If the page is not processed, it will remain, becoming an HTML/XML comment tag. For example:

This assures that the ESI markup will not interfere with the rendering of the final HTML if not processed.

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Notes	2
Help	h

We love Varnish because it's

Varnish Community https://www.varnish-cache.org/

Download & Install

Point Varnish at your web site

Fire up the service

Don't worry you can have your cookies back later!

8 subroutines control how Varnish behaves:

But really it boils down to just vcl_recv() and vcl_fetch().

Processing Client Request

Modify Inbound Request from a Browser

Grabbing the Content Off Your Website

How to Fetch Content

vcl_recv & vcl_fetch

Dealing with non-programmable things

Apache Config: ./virtuals/mysite.conf

For example, flushing the entire site

For example, flushing a specific URL

Allow administrators to easily flush the cache from their browser

Useful if you want content contributors to see "live" content all the time.

Caches everything for anonymous users but gives a pass to authenticated users.

If your website serves different HTML to mobile users, you might use code like this:

For example, caching by user role

Great when you are doing something like Geo-Blocking on the server.

Grace mode

Saint mode

God mode

Shows cache misses by most frequent. Review this periodically for a sanity check on what's not getting cached.

Mash it up in vcl_recv

Fail over for unhealthy servers

Seriously.

Embed ESI tags in your HTML output

Activate ESI processing in your VCL

Keep your application as simple as possible

Set up sub-domains for simple access

Reverse Proxies are FAST

Varnish Cache is awesome

Sixties Air Travel FTW

You have been listening to the dulcet tones of Geoff Bowers (@modius)

URLs that matter

Table of Contents

Help

But really it boils down to just `vcl_recv()` and `vcl_fetch()`.