varnish cache
TRANSCRIPT
Varnish, The Good, The Awesome, and the Downright Crazy
By Mike Willbanks
Sr. Web Architect Manager
NOOK Developer
Northeast PHP August 12, 2012
2
• Talk
Slides will be online later!
• Me
Sr. Web Architect Manager at NOOK Developer
Prior MNPHP Organizer
Open Source Contributor (Zend Framework and various others)
Where you can find me:
• Twitter: mwillbanks G+: Mike Willbanks
• IRC (freenode): mwillbanks Blog: http://blog.digitalstruct.com
• GitHub: https://github.com/mwillbanks
Housekeeping…
3
• What is Varnish
• The Good : Why…
The quick, easy and hardly informed way…
• The Awesome : How…
VCL’s, Directors and more…
• The Crazy : Go…
ESI, Purging, VCL C, and VMOD…
• Varnish Command Line Apps
varnishtop, varnishstat, etc.
Agenda
What is Varnish? Official Statement
What the hell it means
Graphs, oh my!
5
“Varnish is a web application accelerator. You install it in front of your web application and it will speed it up
significantly.”
Official Statement
6
• Varnish allow you to accelerate your website
By using memory and keeping in mind cookies, request headers and more…
• It caches pages so that your web server can RELAX!
What about my apache, tomcat, nginx and (mongrel|thin|goliath….)
Generally caching by TTL + HTTP Headers (cookies too!)
• A load banancer, proxy and more…
What? …. Yes, it can do that!
What The Hell? Tell me!
7
• CaringBridge Status Server
Getting a message to mobile users.
The system is down, or we want to be able to communicate a message to them about some subject… maybe a campaign.
The apps and mobile site rely on an API
• Trouble in paradise? Few and far in between.
Let an API talk to a server…
A story on crashing and burning before varnish.
A General Use Case
8
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
Small X-Large Small Varnish
Time
Time
0
100
200
300
400
500
600
700
Small X-Large Small Varnish
Req/s
Req/s
0
2
4
6
8
10
12
14
Small X-Large Small Varnish
Peak Load
Peak Load
9
The Raw Data
Small X-‐Large Small Varnish Concurrency 10 150 150 Requests 5000 55558 75000 Time 438 347 36 Req/s 11.42 58 585 Peak Load 11.91 8.44 0.35
Comments 19,442 failed reqs
The Good – Listen Up! Installment
Documentation
Finding Existing VCL’s
11
• RTM : http://goo.gl/hl4Tt
Debian: sudo apt-get install varnish
EPEL: yum install varnish
• only 6.x otherwise you’ll be out of date!
WOOT Compiling #git
• git clone git://git.varnish-cache.org/varnish-cache
• cd varnish-cache
• sh autogen.sh
• ./configure
• make && make install
Installment
12
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).
13
• Reference Manual
https://www.varnish-cache.org/docs/3.0/reference/index.html
• Tutorial – more like a book version of the reference manual
https://www.varnish-cache.org/docs/3.0/tutorial/index.html
• Knock yourselves out! There is a ton of documentation
• Yes, this makes happy developers.
Documentation is very accurate, read carefully.
Focus heavily on VCL’s, that is generally what you need.
I’m attempting to show you some of how this works but you will require the documentation to assist you.
Documentation
14
• VCL’s are available for common open source projects
Hi wordpress and drupal!
• https://www.varnish-cache.org/trac/wiki/VarnishAndWordpress
• https://www.varnish-cache.org/trac/wiki/VarnishAndDrupal
Examples of all sorts of crazy
• https://www.varnish-cache.org/trac/wiki/VCLExamples
Existing VCL’s – The truly lazy…
15
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; } }
Wordpress = Bad Slashdot Bad!!!
The Awesome – Going Places VCL
Directors
A Few Examples
17
VCL’s by Diagram…
18
• 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 own VCL
• 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.
VCL – Varnish Configuration Language
19
• vcl_init – VCL is loaded, no request yet; VMOD initialization
• vcl_recv – Beginning of request, req is in scope
• vcl_pipe – Client & backend data passed unaltered
• vcl_pass – Request goes to backend and not cached
• vcl_hash – call hash_data to add to the hash
• vcl_hit – called on request found in the cache
• vcl_miss – called on request not found in the cache
• vcl_fetch – called on document retrieved from backend
• vcl_deliver – called prior to delivery of cached object
• vcl_error – called on errors
• vcl_fini – all requests have exited VCL, cleanup of VMOD’s
VCL – Subroutines – breaking it down.
20
• Always Available
now – epoch time
• Backend Declarations
.host – hostname / IP
.port – port number
• Request Processing
client – ip & identity
server – ip & port
req – request information
VCL - Variables
• Backend Req Prepartion
bereq – backend request
• Retrieved Backend Request
beresp – backend response
• Cached Object
obj – Cached object, can only change .ttl
• Response Preparation
resp – http stuff
21
• hash_data(string) – adds a string to the hash input.
Request host and URL is default from the default vcl.
• regsub(string, regex, sub) – substitution on first occurance
sub can contain numbers 0-n to inject matches from the regex.
• regsuball(string, regex, sub) – substitution on all occurances
• ban(expression) – Ban all objects in cache that match
• ban(regex) – Ban all objects in cache that have a URL match
VCL - Functions
22
• Directors allow you to talk to the backend servers
• Directors are a glorified reverse proxy
Allows for certain types of load balancing
Allows for talking to a cluster
“A director is a logical group of backend servers clustered together for redundancy. The basic role of the director is to let Varnish choose a backend server
amongst several so if one is down another can be used.”
Directors
23
• Random Director – picks a backend by random number
• Client Director – picks a backend by client identity
• Hash Director – picks a backend by URL hash value
• Round-Robin Director – picks a backend in order
• DNS Director – picks a backend by means of DNS
Random OR Round-Robin
• Fallback – picks the first “healthy” backend
Directors – The Types
24
• To ensure healthy backends, you need to use probing.
It really sounds like a colonoscopy for servers; which it is.
• Variables
.url
.request
.window
.threshold
.intial
.expected_response
.interval
.timeout
Director - Probing
25
Example VCL Configuration
The Crazy ESI – Edge-Side Includes
Purging
VMOD
27
• ESI is a small markup language much like SSI (server side includes) to include fragments (or dynamic content for that matter).
• Think of it as replacing regions inside of a page as if you were using XHR (AJAX) but single threaded.
• Three Statements can be utilized.
esi:include – Include a page
esi:remove – Remove content
<!-- esi --> - ESI disabled, execute normally
ESI – Edge Side Includes
28
ESI – By Diagram
29
• In vcl_fetch, you must set ESI to be on
set beresp.do_esi = true;
By default, ESI will still cache, so add an exclusion if you need it
• if (req.url == “/show_username.php”) { return (pass); }
• This is a good thing, you may want to cache user information to the right people (aka by cookie value) so that you don’t reload it on every request.
Varnish refuses to parse content for ESI if it does not look like XML
• This is by default; so check varnishstat and varnishlog to ensure that it is functioning like normal.
Using ESI
30
<html>
<head><title>Rock it with ESI</title></head>
<body>
<header>
<esi:include src="/user_header.php" />
<!-- Don't do this as you'd lose the advantage of varnish -->
<!--esi
<?php include 'user_header.php'; ?>
-->
</header>
<section id="main"></section
<footer></footer>
</body>
</html>
ESI – By Example
31
• The various ways of purging
varnishadm – command line utility
• It’s the ole finger in the back of the throat
Sockets (port 6082) – everyone likes a good socket wrench
• Sure, Ipecac is likely overkill.
HTTP – now that is the sexiness
• A few headers, nothing forced.
Purging
32
varnishadm -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
Purging Examples
33
• Distributed Purging… like a sorority party.
Use a message queue (or gearman job server)
Have a worker that knows about the varnish servers
Submit the request to clear the cache in the asynchronously or synchronously depending on your use case.
• Have enough workers to make this effective at purging the cache quickly.
This will make it far easier to scale; you can either store the servers in a config file, database or anything else you think is relevant.
Distributed Purging
34
• Before getting into VMOD; did you know you can embed C into the VCL for varnish?
• Want to do something crazy fast or leverage a C library for pre or post processing?
• I know… you’re thinking that’s useless..
On to the example; and a good one from the Varnish WIKI!
Embedding C in VCL – you must be crazy
35
C{
#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
VCL - Embedded C for syslog – uber sexy
36
• Taking VCL embedded C to the next level
• Allows you to extend varnish and create new functions
• Now, if you are writing modules for varnish you have a specialty use case!
Go read up on it!
https://www.varnish-cache.org/docs/trunk/reference/vmod.html
VMOD – Varnish Modules / Extensions
37
• The VMOD std is shipped with varnish; it provides some useful commands
toupper
tolower
set_up_tos
random
log
VMOD - std
syslog
fileread
duration
integer
collect
Varnish Command Line Apps varnish varnishadm varnishhist
varnishlog varnishncsa varnishreplay
varnishsizes varnishstat varnishtest
varnishtop
39
• What is varnish doing right now?
• How do I debug what is happening?
varnishtop
What is Varnish doing…
40
What is Varnish doing…
41
• Many times people want to log the requests to a file
By default Varnish only stores these in shared memory.
Apache Style Logs
• varnishncsa –D –a –w log.txt
This will run as a daemon to log all of your requests on a separate thread.
Logging
42
Logging
43
• Need to warm up your cache before putting a sever in the queue or load test an environment?
varnishreplay –r log.txt
• Replaying logs can allow you to do this. This is great for when you are going to be deploying code to check for performance issues.
Although… be careful so that you don’t POST data or create data on peoples accounts. Maybe cat the file and remove anything that executes on data.
Cache Warmup
44
• How to see your cache hit ratios…
varnishstat
• Want to parse them from XML so you can create a sexy administration panel?
varnishstat –x
Cache Hit Ratios? No Problem
45
Cache Hit Ratios? No Problem
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