Evolving Archetecture

Evolving architecture
make development easy and your site faster

Leo Lapworth @ YAPC::EU 2007
http://leo.cuckoo.org/

Covering

How running websites has evolved

Covering

Servers improved

Covering

Servers improved
Architecture improved

Covering

Servers improved
Development tools improved

Covering

Servers improved
Development tools improved
Code (and code libraries) got better

but not...

Covering anything in depth

Concepts stolen from

Mod_perl guide


Mod_perl guide
Léon Brocard


Mod_perl guide
Léon Brocard
Six Apart


Mod_perl guide
Léon Brocard
Six Apart
Yahoo!


Mod_perl guide
Léon Brocard
Six Apart
Yahoo!
+ many other people...


Mod_perl guide
Léon Brocard
Six Apart
Yahoo!
+ many other people...

... this is social Perl

Templates
An example of how things have improved...

Recognise this?
use CGI;
$q = CGI->new();
$name = $q->param('name');
print $q->header('text/html');
$link = 'http://foo.com/';
print quot;<html><head><title>HTML and code
together</title></head><body>quot;;
print quot;<a href=quot;$link/$namequot;>quot;;
print quot;Click here $name</a><br />nquot;;
print quot;<table>quot; . join(quot;nquot;, map {
quot;<tr><td>$_</td></tr>quot;
} qw(this is hard to maintain));
print quot;</table>quot;;

How about...

Now, was it cellspacing, or
cellpadding I need for ie4.02?

and...
I'm a developer, not a designer. I
shouldn't have to know this £@$%!

Use templates...

use Template;

Code, not HTML
use CGI;
use Template;

$q = CGI->new();
print $q->header('text/html');
my %vals = (
name = $q->param('name'),
);

$template =
Template->new({ INCLUDE => '/path/' });
$template->process('hello.html',%vals);

I just code, I have
clean code and I don't
have to know HTML or
browser compatibility
issues

Simple changes make
a huge difference

Single server

Internet

Web server
(static & dynamic)
All editing
Database server

and...

I thought I only
changed one thing, but
it's still broken

1 live server
1 development server

1 live server
1 development server

Internet

Live server Development server

Web server Web server
All editing
(static & dynamic) (static & dynamic)

Database server Database server

Does not solve:

What did I change last?
Who changed what / when?

Version control & docs

Use SVK with Subversion



Clkao - SVK



Use Trac (http://trac.edgewall.org)

Clkao - SVK



- wiki

Clkao - SVK



- wiki
- task tracker

Clkao - SVK



- wiki
- task tracker
- web interface to Subversion

Clkao - SVK

Tests - all you need on one slide


Write tests, write tests often


Run tests, run tests often


Tests are good


Tests are good
Found a bug? - write the test that replicates it.
You know it's ﬁxed when your test passes


Tests are good
Found a bug? - write the test that replicates it.
You know it's ﬁxed when your test passes
Use Test::More, and then test some more!

mod_perl
Code caching (loaded/compiled once)

mod_perl
Server only spends time running the code

mod_perl
Apache::Registry for old/existing code

mod_perl
Apache::SizeLimit (safety net)

mod_perl
Set it high

mod_perl
Set it high
Check it

Front/back end split

Internet

Slow
Back end
Front end
(application server)
Fast
Web server
Web server
(static & proxy to
(dynamic)
application server)
Database server

Development
server

or put another way...

Internet
slow and
demanding
kids
(users)

Canteen

Internet Front end
slow and Dinner-ladies - good at
demanding serving precooked
kids (static) food. Can order
(users) from à la carte chefs
and then serve

Canteen Kitchen

Internet Front end Back end
slow and Dinner-ladies - good at Chefs - good at
demanding serving precooked making à la carte
kids (static) food. Can order (dynamic) food
(users) from à la carte chefs
and then serve

Internet

Slow
Back end
Front end
Fast
Web server
Web server
(static & proxy to
(dynamic)
application server)
Database server

Development
server

Speed up the frequent...

Are you re-creating the same objects/data
structures again and again?

Speed up the frequent...

Are you re-creating the same objects/data
structures again and again?
Can this information persist for a period of
time?

Add caching

Persisting data for a period of time

Add caching

Simple to implement:

Add caching

Does cache exist?

Add caching

Does cache exist?
YES -> retrieve it and return it

Add caching

Does cache exist?
YES -> retrieve it and return it
NO -> create data/object, store in cache
and return it

Things you might cache

Search result sets (a list of ids)


Individual items


Individual items
Look-ups of information from a database


Individual items
Look-ups of information from a database
Fetching of information from external sources

Centralise

Put caching methods in one package

Centralise

Put caching methods in one package
Put any generic methods in a package

We now have a cache

Internet

Slow
Back end
Front end
Fast
Web server
Web server
(static & proxy to Cache
(dynamic)
application server)
Database server

Development
server

We now have a cache

Internet

Slow
Back end
Front end
Fast
Web server
Web server
(static & proxy to Cache
Cache
(dynamic)
application server)
Database server

Development
server

Adding in the cache...

Internet
Kids


Internet Front end
Kids Dinner-ladies


Internet Back end
Front end
Kids Chefs
Dinner-ladies


Cache
Internet Back end
Front end Magic
Kids Chefs
Dinner-ladies freezer

Coping with more trafﬁc
Development
Internet
Stage server server (in the
ofﬁce)

Front end
Back end
Web server (application server)
Database
(static & proxy
server
to application Web server
server) (dynamic)

Back end

Web server
(dynamic)

That's two separate disks

Development
Internet
ofﬁce)

Front end
Back end
Database
(static & proxy
server
to application Web server Cache
server) (dynamic)

Back end

Web server Cache

(dynamic)

Second kitchen, two
freezers...

Second kitchen, two
freezers...

Internet
Kids

Second kitchen, two
freezers...

Internet Front end
Kids Dinner-ladies

Second kitchen, two
freezers...
Kitchen 1

Kitchen 2

Internet Front end Back end
Kids Dinner-ladies Chefs

Second kitchen, two
freezers...
Kitchen 1

Kitchen 2

Internet Front end Back end Cache
Kids Dinner-ladies Chefs Freezers

We want a cache across
servers...

servers...

Enter
Memcache

servers...

Enter
Memcache

See Léon Brocard's talk
at 16:20 for the details

Development
Internet
ofﬁce)

Front end
Back end
Database
(static & proxy
server
to application Web server
server) (dynamic)
Cache

Back end

Web server
(dynamic)

Shared freezer

Internet
Kids

Shared freezer

Internet Front end
Kids Dinner-ladies

Shared freezer

Kitchen 1

Kitchen 2

Internet Front end
Kids Dinner-ladies Back end
Chefs

Shared freezer

Kitchen 1

Kitchen 2

Internet Front end
Kids Dinner-ladies Back end Cache
Chefs Freezer

Maintaining servers
Keep all servers identical where possible

Maintaining servers
Package your code (e.g. .debs)

Maintaining servers
Centralise your crontabs and conﬁguration ﬁles
(and put in version control)

Maintaining servers
Centralise your crontabs and conﬁguration ﬁles
(and put in version control)
Deploy with one script: rsync + ssh + apt-get
update & apt-get upgrade (or your OS
equivalent) to each server

Simplify further
Development
Internet
ofﬁce)

Front end
Back end
Perlbal
Web server
load balancer /
(static+dynamic)
proxy
Database
Cache
server
Back end

Web server
(static+dynamic)

Waiters: cheaper, faster and
less demanding

less demanding

Internet
Kids

less demanding

Front end
Internet
Waiters - good at serving
Kids
quickly and dealing with
annoying customers or
Kitchens

less demanding
Kitchen 1

Kitchen 2

Front end
Internet
Kids Back end
quickly and dealing with
annoying customers or Chefs - simple and complex meals
(static and dynamic)
Kitchens

less demanding
Kitchen 1

Kitchen 2

Front end
Internet
Kids Back end
quickly and dealing with Cache
annoying customers or Chefs - simple and complex meals Freezer
(static and dynamic)
Kitchens

More tips for faster user
experience

mod_gzip

gzip
HTML/css/xml

mod_gzip

gzip
HTML/css/xml Users

mod_gzip

gzip
HTML/css/xml Users

If a browser support compressions... compress
(javascript can be tricky - at least minify)

Cache headers (expiry)

Let web browsers know how long to cache

Cache somethings forever

/includes/js/<VERSION>/common.js



Ensures user has version which matches HTML
(client could have cache of old HTML)



Ensures user has version which matches HTML
(client could have cache of old HTML)
Use include ﬁle to update all pages

Handling images: MogileFS
Store images by group (replication levels)

Spread IO across disks & servers

Retrieve from fastest server

Integrate with Perlbal, hidden from the user

Integrate with Perlbal, hidden from the user
Automatic resilience

Basic rules to consider
Centralise (code/templates/conﬁguration/
deployment etc)

deployment etc)
Test, run lots of them

deployment etc)
Cache if you need it; memcache is great

deployment etc)
Keep is simple (perlbal especially)

deployment etc)
Keep is simple (perlbal especially)
Sometimes it's just easier to buy another server
(this is not always true)

We covered...
perlbal
memcached

We covered...
perlbal
memcached
svk (subversion)

We covered...
perlbal
memcached
svk (subversion)
trac

We covered...
perlbal
memcached
svk (subversion)
trac
rsync

We covered...
perlbal
memcached
svk (subversion)
trac
rsync
gzip

We covered...
perlbal mogileFS
memcached
svk (subversion)
trac
rsync
gzip

We covered...
perlbal mogileFS
server architecture
memcached
svk (subversion)
trac
rsync
gzip

We covered...
perlbal mogileFS
server architecture
memcached
Test::More
svk (subversion)
trac
rsync
gzip

We covered...
perlbal mogileFS
server architecture
memcached
Test::More
svk (subversion)
mod_perl
trac
rsync
gzip

We covered...
perlbal mogileFS
server architecture
memcached
Test::More
svk (subversion)
mod_perl
trac
Template::Toolkit
rsync
gzip

We covered...
perlbal mogileFS
server architecture
memcached
Test::More
svk (subversion)
mod_perl
trac
Template::Toolkit
rsync
HTTP Cache headers
gzip

We covered...
perlbal mogileFS
server architecture
memcached
Test::More
svk (subversion)
mod_perl
trac
Template::Toolkit
rsync
HTTP Cache headers
gzip

and...

...how a kitchen should run

Any questions?

Evolving architecture
http://leo.cuckoo.org/projects/ea/

Leo Lapworth
http://leo.cuckoo.org/

Evolving Archetecture

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