Nice performance using Sf2 cache wrapping Sf1 application - Paris

Nice performance using SF2 cache wrapping sf1 application Marc Weistroff Emmanuel Cohen Sf Live SF 2011 Thursday, March 3 2011

Who we are
Emmanuel Cohen
Project manager at Sensio Labs
4 year experience with PHP5
5+ year experience with Java EE
Learned Basic on Amstrad CPC 6128

Who we are
Marc Weistroff
Developer at Sensio Labs since 11/2009
Lead developer on this project
Experiences with C, and PHP from version 3
Encountered programming with Amos Basic on Amiga 500

This talk
Symfony2
symfony 1
HTTP Cache
Edge Side Includes (ESI)
Web architecture
Online media

Our client
L’Express Magazine
Express-Roularta Group
Magazine created in 1953
http://www.lexpress.fr
Top 3 French online news
Need for speed!

The project
A cultural knowledge base
A bridge between hot news and cultural knowledge
An extension of www.lexpress.fr

Technical objectives
Performance
A full scale Proof-of-Concept for the future
Keep it Simple

Constraints
Heterogeneous XML Sources
Solution based on symfony 1
Adaptability (for future extensions)

How does this app work ?

Our symfony 1 application design HTML Renderer XML Server OCARI Culture OCARI Content
Stores
Normalizes
Aggregates
Serves XML
Sources deliver heterogeneous data
Renders HTML with XSL
Renders static layouts

Our symfony 1 application design
Highly specialized applications
Loose coupling
Front dedicated to delivering content fast

Addressing performance with Symfony2

Addressing performance with Sf2
With Symfony2 built-in Gateway :
HTTP cache
ESI : Edge Side Includes

Performance with Symfony2 : HTTP Cache
HTTP RFC
http://tools.ietf.org/wg/httpbis/
http://tools.ietf.org/html/draft-ietf-httpbis-p6-cache-12

Symfony2 uses HTTP cache headers to handle cache
s-maxage or max-age
Etag, Last-Modified, If-Modified-Since
http://tools.ietf.org/html/draft-ietf-httpbis-p6-cache-12

symfony 1
Applicative cache
Symfony2
Light-weight HttpKernel
The application is not hit
Supports a standard

Find out what’s stale
The problem of invalidation
Performance with Symfony2: Cache issues

Selective caching
Do not regenerate the whole page when you just need to regenerate small parts of it
Performance with Symfony2: Cache issues

Performance with Symfony2: ESI
Edge-Side include: A markup language
W3C note from Akamai
http:// www.w3.org/TR/esi-lang
http:// www.akamai.com/html/support/esi.html

ESI : A page in lexpress.fr

Each fragment has its own ttl or validation rule => the fragments are selectively refreshed

Dependance is defined once and for all
In expiration: simply set your ttl for each fragment

How does ESI work?

Represented by an HTML Tag
<esi:include src=“/movie/dogma/critics” />
Processed by a proxy
Transformed into HTTP Request to the application
Response is inserted in place of the esi tag
HTTP cache is handled independently for each esi tag

/movie/dogma

Html Fragment
Pure HTML
Inserted in lieu of the <esi /> tag
No <html>, <body> or <head> tag in this case

What you need
Any client!
A proxy that handles ESI (ie: Varnish or Symfony2)
An application that delivers HTML and HTTP cache headers
Serve HTML pages that contain ESI tags

First request ever Client Proxy Application /movie/dogma /movie/dogma miss Cache-Control: s-maxage=600 /movie/dogma/casting /movie/dogma/critics Cache-Control: s-maxage=3600 Cache-Control: s-maxage=300

Request at t+200 Client Proxy Application /movie/dogma hit

The application is never hit! As if the complete page was cached in the reverse proxy

Request at t+500 Client Proxy Application /movie/dogma /movie/dogma/critics Cache-Control: s-maxage=300 hit

The application is partially hit And has to build only a small fragment of the page

Pros
You use HTTP cache, not the application one.
Performance improvements!
Granularity: Different cache strategy or TTL on different parts of your page

Cons
Your app will be hit n times upon the very first request
Your app have to be designed to support the rendering of fragments

But our app is symfony 1 right ?

What to do with your symfony 1 application when you are dying to use Symfony2?
Wrap it. Our app is symfony 1

Our symfony 1 application design HTML Renderer XML Server OCARI Culture OCARI Content Symfony1 wrapper Edge side Symfony2
Stores
Normalizes
Aggregates
Serves XML
Sources deliver heterogeneous data
Renders HTML with XSL
Renders static layouts

Wrapping symfony 1 with Symfony2

Constraint
We use the Symfony2 ESI/Cache proxy
All the call to our app is done in the same PHP process

symfony 1 needs tweaking in order to work around a few obstacles

Which ones ?
It is not reentrant
sfConfig singleton
sfContext singleton
It sends the response directly to the client
Filter chain execution
At the end, sfRenderingFilter sends the complete response

What about Symfony2?
Better architecture: Symfony2 is reentrant
Symfony2 is heavily based on interfaces
Symfony2 is divided into several components
HttpKernelHttpKernelInterface

HttpKernelHttpKernelInterface
Lightweight (1 method)
Forces to implement a “handle” method that accepts a Symfony2 Request object and returns a Symfony2 Response object
Used by all the classes that act as a Kernel in Symfony2 (ie: HttpKernelHttpCache)

Addressing the issues
Reentrance
Override the super globals
Create a fresh new context each time
Filter chain
Replace sfRenderingFilter by a noRenderingFilter class
Create a Symfony2 Response object and returns it

Final app architecture EsiCacheKernel SymfonyWrapperKernel symfony 1 application

https://github.com/marcw/sflive-2011

Then… You have to design your app to serve HTML fragments!

Designing your app
Don’t think partials or components, think actions!
Actions render HTML fragments
Actions MUST define explicitly the response cache headers.

And now where happy

Or are we ?

Our choices
The choice of symfony 1
The choice of Symfony2
The choice to mix
Expiration over validation

This is symfony1 : DO NOT TRY ANY OF THIS AT HOME!

Our results
It works!
The frontend is scalable and extensible
Performance is nice, but we needed to improve the Store.php class

What to do next ?

Implementing cache validation
The application needs to garantee freshness
How to avoid hitting the application ?

Proxy ESI New response Or 304 URL-> {ETag} ETag-> lastmodified If Etag absent or stale Response with HTTP headers Etag LastModified Client Request with HTTP headers If-None-Match If-Modified-Since App New response Or 304 If cache entry is not fresh enough Cache Validation Optimizer

Contact @ L’Express
Sébastien Angèle
[email_address]
Jérôme Macias
[email_address]

Questions ?
Marc Weistroff
@futurecat
[email_address]
http://www.marcw.net
Emmanuel Cohen
@emmanuelcohen
[email_address]

Thank you! Please rate this talk at http://joind.in/2749

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Nice performance using Sf2 cache wrapping Sf1 application - Paris

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