Lightning fast

Using Varnish to accelerate your web applications

By Thijs Feryn

Slow websites suck

Web performance is an essential part of the

user experience

Down

Slowdown ~ downtime

Hi, I’m Thijs

I’m @ThijsFeryn on Twitter

I’m an Evangelist

At

Mo moneyMo servers

Write better code

Cache

Don’t recompute if the data

hasn’t changed

How does Varnish work?

Normally

User Server

With Varnish

User Varnish Server

Why is it so good?

Smart kernel tricks

Stores HTTP output in memory*

Respects HTTP best

practices

Varnish Configuration Language

What about TLS/SSL?

Quick install

& configure

apt-get install apt-transport-https curl https://repo.varnish-cache.org/GPG-key.txt | apt-key add - echo "deb https://repo.varnish-cache.org/debian/ jessie varnish-4.1"\ >> /etc/apt/sources.list.d/varnish-cache.list apt-get update apt-get install varnish

Install on Linux (Debian)

There's stuff for Ubuntu, RHEL

& CentOS too

-a :80 \ -a :81,PROXY \ -T localhost:6082 \ -f /etc/varnish/default.vcl \ -S /etc/varnish/secret \ -s malloc,3g \ -j unix,user=myUser

Simple config

Varnish speaks HTTP

✓Idempotence ✓State ✓Expiration ✓Conditional requests ✓Cache variations

Varnish speaks HTTP

✓GET ✓HEAD -POST -PUT -PATCH -DELETE -TRACE -OPTIONS

Idempotency

Only cache GET & HEAD

✓Doesn't cache when cookies are present ✓Doesn't cache when cookies are set ✓Doesn't cache when Autorization headers are present

State

Avoids caching user-

specific contentAffects hit

rate

Expiration

Expires: Sat, 09 Sep 2017 14:30:00 GMT

Cache-control: public, max-age=3600, s-maxage=86400

Cache-control: private, no-cache, no-store

Expiration precedence

1. beresp.ttl (VCL) 2. s-maxage 3. max-age 4. expires 5. 120 seconds by default

Conditional requests

HTTP/1.1 200 OK Host: localhost Etag: 7c9d70604c6061da9bb9377d3f00eb27 Content-type: text/html; charset=UTF-8

Hello world output

GET /if_none_match.php HTTP/1.1 Host: localhost User-Agent: curl/7.48.0

Conditional requests

HTTP/1.0 304 Not Modified Host: localhost Etag: 7c9d70604c6061da9bb9377d3f00eb27

GET /if_none_match.php HTTP/1.1 Host: localhost User-Agent: curl/7.48.0 If-None-Match: 7c9d70604c6061da9bb9377d3f00eb27

Conditional requests

HTTP/1.1 200 OK Host: localhost Last-Modified: Fri, 22 Jul 2016 10:11:16 GMT Content-type: text/html; charset=UTF-8

Hello world output

GET /if_none_match.php HTTP/1.1 Host: localhost User-Agent: curl/7.48.0

Conditional requests

HTTP/1.0 304 Not Modified Host: localhost Last-Modified: Fri, 22 Jul 2016 10:11:16 GMT

GET /if_none_match.php HTTP/1.1 Host: localhost User-Agent: curl/7.48.0 If-Last-Modified: Fri, 22 Jul 2016 10:11:16 GMT

✓Hostname (or IP) ✓URL

Cache variations

Identify object in

cache

Cache variationsGET / HTTP/1.1 Host: localhost Accept-Language: nl

HTTP/1.1 200 OK Host: localhost Vary: Accept-Language

Hallo, deze pagina is in het Nederlands geschreven.

Built-in VCL cheat sheet

✓Only GET & HEAD ✓No Cookie ✓No Authorization

Built-in VCL (frontend)

Lookup in cache

Otherwise pass and don't

cache

✓No Set-Cookie ✓TTL > 0 ✓No "no-cache", "private", "no-store"

Built-in VCL (backend)

Store in cacheOtherwise

blacklist for 120s

The actual VCL code

sub vcl_recv { if (req.method == "PRI") { /* We do not support SPDY or HTTP/2.0 */ return (synth(405)); } if (req.method != "GET" && req.method != "HEAD" && req.method != "PUT" && req.method != "POST" && req.method != "TRACE" && req.method != "OPTIONS" && req.method != "DELETE") { /* Non-RFC2616 or CONNECT which is weird. */ return (pipe); }

if (req.method != "GET" && req.method != "HEAD") { /* We only deal with GET and HEAD by default */ return (pass); } if (req.http.Authorization || req.http.Cookie) { /* Not cacheable by default */ return (pass); } return (hash); }

sub vcl_pipe { # By default Connection: close is set on all piped requests, to stop # connection reuse from sending future requests directly to the # (potentially) wrong backend. If you do want this to happen, you can undo # it here. # unset bereq.http.connection; return (pipe); }

sub vcl_pass { return (fetch); }

sub vcl_hash { hash_data(req.url); if (req.http.host) { hash_data(req.http.host); } else { hash_data(server.ip); } return (lookup); }

sub vcl_purge { return (synth(200, "Purged")); }

sub vcl_hit { if (obj.ttl >= 0s) { // A pure unadultered hit, deliver it return (deliver); } if (obj.ttl + obj.grace > 0s) { // Object is in grace, deliver it // Automatically triggers a background fetch return (deliver); } // fetch & deliver once we get the result return (miss); }

sub vcl_miss { return (fetch); }

sub vcl_deliver { return (deliver); }

sub vcl_backend_fetch { return (fetch); }

sub vcl_backend_response { if (beresp.ttl <= 0s || beresp.http.Set-Cookie || beresp.http.Surrogate-control ~ "no-store" || (!beresp.http.Surrogate-Control && beresp.http.Cache-Control ~ "no-cache|no-store|private") || beresp.http.Vary == "*") { /* * Mark as "Hit-For-Pass" for the next 2 minutes */ set beresp.ttl = 120s; set beresp.uncacheable = true; } return (deliver); }

Reality sucks

Cache-control ?

Legacy

Write VCL

Normalize

vcl 4.0;import std;

sub vcl_recv { set req.http.Host = regsub(req.http.Host, ":[0-9]+", "");

set req.url = std.querysort(req.url);

if (req.url ~ "\#") { set req.url = regsub(req.url, "\#.*$", ""); }

if (req.url ~ "\?$") { set req.url = regsub(req.url, "\?$", ""); }

if (req.restarts == 0) { if (req.http.Accept-Encoding) { if (req.http.User-Agent ~ "MSIE 6") { unset req.http.Accept-Encoding; } elsif (req.http.Accept-Encoding ~ "gzip") { set req.http.Accept-Encoding = "gzip"; } elsif (req.http.Accept-Encoding ~ "deflate") { set req.http.Accept-Encoding = "deflate"; } else { unset req.http.Accept-Encoding; } } }}

sub vcl_recv { if (req.url ~ "^/status\.php$" || req.url ~ "^/update\.php$" || req.url ~ "^/admin$" || req.url ~ "^/admin/.*$" || req.url ~ "^/user$" || req.url ~ "^/user/.*$" || req.url ~ "^/flag/.*$" || req.url ~ "^.*/ajax/.*$" || req.url ~ "^.*/ahah/.*$") { return (pass); }}

URL blacklist

sub vcl_recv { if (req.url ~ "^/products/?" return (hash); }}

URL whitelist

Cookies

vcl 4.0;

sub vcl_recv { set req.http.Cookie = regsuball(req.http.Cookie, "has_js=[^;]+(; )?", ""); set req.http.Cookie = regsuball(req.http.Cookie, "__utm.=[^;]+(; )?", ""); set req.http.Cookie = regsuball(req.http.Cookie, "_ga=[^;]+(; )?", ""); set req.http.Cookie = regsuball(req.http.Cookie, "_gat=[^;]+(; )?", ""); set req.http.Cookie = regsuball(req.http.Cookie, "utmctr=[^;]+(; )?", ""); set req.http.Cookie = regsuball(req.http.Cookie, "utmcmd.=[^;]+(; )?", ""); set req.http.Cookie = regsuball(req.http.Cookie, "utmccn.=[^;]+(; )?", ""); set req.http.Cookie = regsuball(req.http.Cookie, "__gads=[^;]+(; )?", ""); set req.http.Cookie = regsuball(req.http.Cookie, "__qc.=[^;]+(; )?", ""); set req.http.Cookie = regsuball(req.http.Cookie, "__atuv.=[^;]+(; )?", ""); set req.http.Cookie = regsuball(req.http.Cookie, "^;\s*", "");

if (req.http.cookie ~ "^\s*$") { unset req.http.cookie; }}

Remove tracking cookies

vcl 4.0;

sub vcl_recv { 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, ";(PHPSESSID)=", "; \1="); set req.http.Cookie = regsuball(req.http.Cookie, ";[^ ][^;]*", ""); set req.http.Cookie = regsuball(req.http.Cookie, "^[; ]+|[; ]+$", "");

if (req.http.cookie ~ "^\s*$") { unset req.http.cookie; } }}

Only keep session cookie

sub vcl_recv { 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, ";(language)=", "; \1="); set req.http.Cookie = regsuball(req.http.Cookie, ";[^ ][^;]*", ""); set req.http.Cookie = regsuball(req.http.Cookie, "^[; ]+|[; ]+$", "");

if (req.http.cookie ~ "^\s*$") { unset req.http.cookie; return(pass); }

return(hash); }}

sub vcl_hash { hash_data(regsub( req.http.Cookie, "^.*language=([^;]*);*.*$", "\1" ));}

Language cookie cache variation

Alternative language cache

variation

sub vcl_hash { hash_data(req.http.Accept-Language);}

HTTP/1.1 200 OK Host: localhost Vary: Accept-Language

Hash language

Or just use

Cookie guidelines

✓Don't throw everything in a session ✓Use dedicated cookies ✓Strip off tracking cookies in VCL ✓Match cookies in VCL & make decisions ✓Perform cache variations on cookie values ✓Only use session cookies when you really have to ✓Use JWT to store session state client-side

Cookie guidelines

Block caching

Code renders

single HTTP response

Lowest denominator:

no cache

<esi:include src="/header" />

Edge Side Includes

✓Placeholder ✓Parsed by Varnish ✓Output is a composition of blocks ✓State per block ✓TTL per block

sub vcl_recv { set req.http.Surrogate-Capability = "key=ESI/1.0";}

sub vcl_backend_response { if (beresp.http.Surrogate-Control ~ "ESI/1.0") { unset beresp.http.Surrogate-Control; set beresp.do_esi = true; }}

Edge Side Includes

ESI vs

AJAX

<esi:include src="/header" />

Choose wisely

<hx:include src="/header"></hx:include>

ESI, parsed by Varnish

HInclude, parsed by Javascript

Breaking news isn't breaking

Purging

acl purge { "localhost"; "127.0.0.1"; "::1";}

sub vcl_recv { if (req.method == "PURGE") { if (!client.ip ~ purge) { return (synth(405, “Not allowed.”)); } return (purge); }}

Purging

acl purge { "localhost"; "127.0.0.1"; "::1";}

sub vcl_backend_response { set beresp.http.x-url = bereq.url; set beresp.http.x-host = bereq.http.host; }

sub vcl_deliver { unset resp.http.x-url; unset resp.http.x-host; }

sub vcl_recv { if (req.method == "PURGE") { if (!client.ip ~ purge) { return (synth(405, "Not allowed")); } if(req.http.x-purge-regex) { ban("obj.http.x-host == " + req.http.host + " && obj.http.x-url ~ " + req.http.x-purge-regex); } else { ban("obj.http.x-host == " + req.http.host + " && obj.http.x-url == " + req.url); } return (synth(200, "Purged")); }}

Banning

Banningcurl -XPURGE "http://example.com/products"

curl -XPURGE -H "x-purge-regex:/products" \ "http://example.com"

varnishadm> ban obj.http.x-host == example.com && obj.http.x-url ~ ^/product/[0-9]+/details

Want more?

VMODs

Write less VCL

Write more code

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