The careerswales.com platform manages the education and professional progression of millions of people in Wales. When challenged with upgrading its ageing application stack to suit modern standards, we devised a solution with Symfony2 at its core. In this talk I'll discuss how the new stack was implemented, focussing on how we took advantage of Symfony2's first-class support for reverse-proxy Varnish to phase the deployment of the new system and improve performance by a significant amount. I'll also talk about the API we created to bridge its SQL Server / MySQL database platforms, and how Symfony2 was used to provide a single-sign-on solution across all of its web applications.

1. Transforming legacy
applications with Symfony2
and Varnish

4. JULY 2012
10 CONCURRENT USERS
~20 SECONDS AVERAGE
HOMEPAGE -> LOGIN -> PERSONAL DETAILS

5. Why so slow?
PHP4
SQL Server and Windows Server
Sub-optimal caching strategy

7. “Rewriting the code from scratch ... (is) the single
worst strategic mistake a software company can
make.”
- Joel Spolsky

8. “... the quick fix is like quicksand: The clarity of
code goes down and confusion is harvested in its
place.”
- Venkat Subramaniam and Andy Hunt

9. The Plan
Reduce cost, improve performance
Develop new application framework
Gradual deployment to careerswales.com
API to access shared data
Single sign on and shared sessions

10. Legacy CMS New Applications
CAREERSWALES.COM

11. ... ENTER SYMFONY2

12. Why Symfony2?
Used successfully in other projects
Excellent 3rd party libraries
Flexible and easy to extend
Facilitates best practice

13. PART 1: THE CMS

14. Catalyst CMS
Cutting edge stack - PHP 5.4, Nginx, FPM
Reusable code through Symfony2 bundles
Inspired by Symfony2 CMF and Sonata
Fraction of the code to maintain

16. PART 2: THE API

17. Take it to the bridge
Bridges MSSQL & MySQL databases
Acts as a facade
Linux + MSSQL = PAIN
Caching with Symfony2 and Doctrine

18. SQL
Server
API
Application
(Symfony2)
Third parties
MySQL
Website
Application
(Symfony2)

19. PART 3: SINGLE SIGN ON

20. Single sign on
Single authentication system for all applications
Uses Central Authentication Service (CAS)
protocol
BeSimpleSsoAuthBundle does heavy lifting
Custom modifications via DI container

21. PART 4: VARNISH

22. Varnish
Frontend proxy or HTTP accelerator
Sits between client and server
Shares cached responses between clients
Can perform load balancing and routing

23. Without Varnish
Client
Client
Client
HTTP://WWW.CAREERSWALES.COM/EN/

24. Without Varnish
Client
Client
Client
TTL = 1 DAY
TTL = 1 DAY
TTL = 1 DAY
HTTP://WWW.CAREERSWALES.COM/EN/

25. With Varnish
Client
Client
Client
Varnish
HTTP://WWW.CAREERSWALES.COM/EN/

26. With Varnish
Client
Client
Client
Varnish
TTL = 1 DAY
TTL = 1 DAY
TTL = 1 DAY
TTL = 1 DAY
HTTP://WWW.CAREERSWALES.COM/EN/

27. With Varnish
Client
Client
Client
Varnish
Client
Client Client Client
HTTP://WWW.CAREERSWALES.COM/EN/

28. With Varnish
Client
Client
Client
Varnish
Client
Client Client Client
HTTP://WWW.CAREERSWALES.COM/EN/

29. ESI Caching
Edge Side Includes
Identifies blocks of HTML which are dynamic
Blocks are independent of the main response
Blocks can be cached and expired individually
Blocks can be identified as public (cacheable) or
private (not cacheable)

30. TTL = 5 MINS
TTL = 5 DAYS

31. INVALIDATED
INVALIDATED
INVALIDATED

32. Carousel Block Caching
Straightforward caching
No personalisation, same for all users

33. Carousel Block Caching
public function indexAction()
{
$response = new Response();
// cache for 1 minute
$response->setMaxAge(60);
$response->setPublic();
return $this->render(
'BoxUK:Default:index.html.twig',
array(),
$response
);
}

34. Login Button Caching
More complex: two different states
Can use varying to store two different caches
Use cookies to provide information to Varnish
BUT don’t want to vary on cookie

35. Login Button Caching
public function indexAction()
{
$response = new Response();
// cache for 1 minute
$response->setMaxAge(60);
$response->setPublic();
$response->setVary('Logged-In');
return $this->render(
'BoxUK:Default:index.html.twig',
array(),
$response
);
}

36. Login Button Caching
public function onKernelResponse(
FilterResponseEvent $event
)
{
$response = $event->getResponse();
$loggedIn = $this->context->isGranted(
'IS_AUTHENTICATED_FULLY'
) ? 'true' : 'false';
$response
->headers
->set('Logged-In', $loggedIn);
}

37. Login Button Caching
public function onKernelResponse(
FilterResponseEvent $event
)
{
$response = $event->getResponse();
$cookie = new Cookie('Logged-In',
$loggedIn, ...);
$response
->headers
->setCookie($cookie);
}

38. Login Button Caching
if (req.http.Cookie ~ 'Logged-In=true') {
set req.http.Logged-In = 'true';
}
Varnish cache keys are hashed on URL (host, path,
etc) and vary data
Symfony takes care of the way out
On the way in, we have to fake the header to
reproduce the hash

39. Routing
Varnish directs requests to given ‘backends’
Load balancing, e.g. round robin
More complex logic via VCL (Varnish Configuration
Language)
No EC2 load balancers!

40. Routing
Old
applications
New
applications
10.1.2.1
10.1.2.2
Client Varnish
Examine
request

41. Defining backends
backend legacy_applications {
.host = "10.1.2.1";
.port = "80";
}
backend new_applications {
.host = "10.1.2.2";
.port = "80";
}

42. Routing by regex
sub vcl_recv {
! if (req.url ~
"^(.*)www.careerswales.com/old-request-format") {
! set req.backend = legacy_applications;
! return(pipe);
! }
! if (req.url ~
"^(.*)www.careerswales.com/new-request-format") {
! set req.backend = new_applications;
! return(pipe);
! }
}

43. OLD APPLICATIONS
Client
Varnish
NEW APPLICATIONS
SQL
Server
MySQL
SSO
App
API
APP
www.careerswales.com
/old-request-format
www.careerswales.com
/new-request-format

44. JULY 2012
10 CONCURRENT USERS
~20 SECONDS AVERAGE
HOMEPAGE -> LOGIN -> PERSONAL DETAILS

45. JULY 2013
10 CONCURRENT USERS
~4 SECONDS AVERAGE
HOMEPAGE -> LOGIN -> PERSONAL DETAILS

46. Conclusions
Observable speed increase of 560%No loss of
functionality or downtime
No loss of functionality or downtime
Substantially less ‘hardware’
More complex environment

49. Questions?
@craigmarvelley