IPC Varnish

7/27/2019 IPC Varnish

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Mike Willbanks | Barnes & Noble

Varnish Cache



Housekeeping…

• Talk

– Slides will be posted after the talk.

• Me – Sr. Web Architect Manager at NOOK

Developer

– Prior MNPHP Organizer

– Open Source Contributor

– Where you can find me:• Twitter : mwillbanks G+: Mike Willbanks

• IRC (freenode): mwillbanks Blog:http://blog.digitalstruct.com

• GitHub: https://github.com/mwillbanks



Agenda• Varnish?

• The Good : Getting Started

•

The Awesome : General Usage• The Crazy : Advanced Usage

• Gotchas



WHAT IS VARNISH?

Official StatementWhat it does

General use case



Official Statement

“Varnish is a web application accelerator. You install it in front of your web application and it will speed it

up significantly.”









You can cache…

Both dynamic and static files and contents.



A Scenario• System Status Server

– Mobile apps check current status.

– If the system is down do we communicate?

– If there are problems do we communicate?

– The apps and mobile site rely on an API

• Trouble in paradise? Few and far in between.



The Graph - AWS

0

10000

20000

30000

40000

50000

60000

70000

80000

Small X-Large Small Varnish

Requests

Requests

0

50

100

150

200

250

300

350

400

450

500


Time

Time

0

2

4

6

8

10

12

14


Peak Load

Peak Load

0

100

200

300

400

500

600

700


Req/s

Req/s



The Raw DataSmall X-Large SmallVarnish

Concurrency 10 150 150

Requests 5000 55558 75000

Time 438 347 36Req/s 11.42 58 585

PeakLoad 11.91 8.44 0.35

Comments

19,442failed

requests



Traditional LAMP Stack

HTTP Server Cluster

Database

Load Balancer





THE GOOD – JUMP START

Installation

General Information

Default VCL



Installationrpm --nosignature -i http://repo.varnish-cache.org/redhat/varnish-3.0/el5/noarch/varnish-release-3.0-1.noarch.rpm

yum install varnish

curl http://repo.varnish-cache.org/debian/GPG-key.txt | sudo apt-key add -echo "deb http://repo.varnish-cache.org/ubuntu/ lucid varnish-3.0" | sudo

tee -a /etc/apt/sources.listsudo apt-get update

sudo apt-get install varnish

git clone git://git.varnish-cache.org/varnish-cachecd varnish-cache

sh autogen.sh./configure

make && make install



Varnish Daemon• varnishd

– -a address[:port] listen for client

– -b address[:port] backend requests

– -T address[:port] administration http

– -s type[,options] storage type (malloc, file,persistence)

– -P /path/to/file PID file – Many others; these are generally the most

important. Generally the defaults will do with just modification of the default VCL (more on it

later).







So what’s actually caching?• Any requests containing

– GET / HEAD

– TTL > 0

• What cause it to miss?

– Cookies

– Authentication Headers

– Vary “*”

– Cache-control: private





HTTP Caching• RFC 2616 HTTP/1.1 Headers

– Expiration

• Cache-Control

• Expires

– Validation

• Last Modified

• If-Modified-Since

• ETag

• If-None-Match



TTL Priority• VCL

– beresp.ttl

• Headers

– Cache-control: s-max-age

– Cache-control: max-age

– Expires

– Validation



Use Wordpress?backend default {

.host = "127.0.0.1“;

.port = "8080";

}

sub vcl_recv {

if (!(req.url ~ "wp-(login|admin)")) {unset req.http.cookie;

}

}

sub vcl_fetch {if (!(req.url ~ "wp-(login|admin)")) {

unset beresp.http.set-cookie;

}}





Varnish Configuration

Language• VCL State Engine

– Each Request is Processed Separately &Independently

– States are Isolated but are Related – Return statements exit one state and start another

– VCL defaults are ALWAYS appended below your ownVCL

• VCL can be complex, but…

– Two main subroutines; vcl_recv and vcl_fetch – Common actions: pass, hit_for_pass, lookup, pipe,

deliver

– Common variables: req, beresp and obj

– More subroutines, functions and complexity can arise

dependent on condition.



Request

Response

vcl_recv

re q.

vcl_hash

vcl_hit

vcl_miss

vcl_fetch

vcl_deliver

re q.

re q.

o b j.

res p.

re q.

bere q.

beres p.

re q.

bere q.

vcl_pipe

re q.

bere q.

vcl_pass

re q.

bere q.





















vcl_fetch• Fetch retrieves the response from the

backend.

• No Cache if …

– TTL is not set or not greater than 0.

– Vary headers exist.

– Hit-For-Pass means we will cache a passthrough.



GENERAL ADJUSTMENTS

Common adjustments to make.











Directors – The TypesDirector Type Description

Random Picks based on random and weight.

Client Picks based on client identity.

Hash Picks based on hash value.

Round Robin Goes in order and starts over

DNS Picks based on incoming DNS host,random OR round robin.

Fallback Picks the first “healthy” server.





Load Balancing

Implementing a simple varnish load balancer.

Varnish does not handle SSL termination.







Purging• The various ways of purging

– varnishadm – command line utility

– Sockets (port 6082) – HTTP – now that is the sexiness



Purging Examplesvarnishadm -T 127.0.0.1:6082 purge req.url == "/foo/bar“

telnet localhost 6082

purge req.url == "/foo/bar

telnet localhost 80

Response:

Trying 127.0.0.1...

Connected to localhost.

Escape character is '^]'.

PURGE /foo/bar HTTP/1.0

Host: bacon.org

curl –X PURGE http://bacon.org/foo/bar



Distributed Purging• curl multi-request (in php)

• Use a message queue

– Use workers to do the leg work for you

• You will need to store a list of servers “somewhere”







VERIFY YOUR VCL

You likely want to ensure that your cache is:

1. Working Properly

2. Caching Effectively



What is Varnish doing…

Varnishtop will show you real time information on your system.

• Use -i to filter on specific tags.

• Use -x to exclude specific tags.





THE CRAZY

ESI – Edge-Side Includes

Varnish Administration

VMOD



ESI – Edge Side Includes

• ESI is a small markup language much likeSSI (server side includes) to includefragments (or dynamic content for that

matter).• Think of it as replacing regions inside of a

page as if you were using XHR (AJAX) butsingle threaded.

• Three Statements can be utilized. – esi:include – Include a page

– esi:remove – Remove content

–  - ESI disabled, execute normally



ESI Diagram

Page Content

<esi:includesrc="header.php" />

Backend

Varnish

Varnish detects ESI, requests from backend OR checks cachedstate.





ESI Usage<html>

<head><title>Rock it with ESI</title></head>

<body>

<header>

<esi:include src=”header.php" />

</header>

<section id="main">...</section>

<footer></footer>

</body>

</html>





Embedded C for syslogC{

#include <syslog.h>

}C

sub vcl_something {

C{

syslog(LOG_INFO, "Something happened at VCL line XX.");

}C

}

# Example with using varnish variables

C{

syslog(LOG_ERR, "Spurious response from backend: xid %s request %s%s \"%s\" %d \"%s\" \"%s\"", VRT_r_req_xid(sp),

VRT_r_req_request(sp), VRT_GetHdr(sp, HDR_REQ, "\005host:"),

VRT_r_req_url(sp), VRT_r_obj_status(sp), VRT_r_obj_response(sp),VRT_GetHdr(sp, HDR_OBJ, "\011Location:"));

}C



Varnish Modules / Extensions

• Taking VCL embedded C to the next

level

• Allows you to extend varnish and createnew functions

• You could link to libraries to provide

additional functionality



VMOD - std

• toupper

• tolower

• set_up_tos• random

• log

• syslog

• fileread

• duration• integer

• collect





Management Console

• varnishadm –T localhost:6062

– vcl.list – see all loaded configuration

– vcl.load – load new configuration – vcl.use – select configuration to use

– vcl.discard – remove configuration





GOTCHAS

Having Keep-Alive off

No SSL Termination

No persistent cache

ESI multiple fragments

Cookies*



QUESTIONS?

These slides will be posted to SlideShare & SpeakerDeck.

SpeakerDeck: http://speakerdeck.com/u/mwillbanks

Slideshare: http://www.slideshare.net/mwillbanks

Twitter: mwillbanks

G+: Mike Willbanks

IRC (freenode): mwillbanks

Blog: http://blog.digitalstruct.com GitHub: https://github.com/mwillbanks

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