enhancing scalability with intelligent caching

© All rights reserved. Zend Technologies, Inc.

Enhancing Scalability

With Intelligent Caching

By Eric Ritchie ([email protected])


Eric Ritchie bids you welcome!

• Senior Technical Consultant and Trainer at Zend Technologies

• Zend Framework and PHP 5.3 ZCE

• Eighteen years of system administration experience

• Twelve years of PHP (3,4 & 5) and five years Zend

Framework development experience

• Hobbies: Sampling good wines/whiskies (gifts welcome)


• Most caching is badly implemented

• Allow me to explain...

Why am I here?


• A new website is born...

Hey, it works!

Internet

LAMP Server


• the smoke begins...

...or at least it used to work.

Internet

LAMP Server


• Migrating to web clusters:

Classical horizontal scaling

Complicates and imbalances application architecture

Moves bottlenecks over to the DB (usually)

• Scaling DB architecture:

Potentially expensive

Or complicates the application (sharding)

And/or replication issues

• Let‘s just cache something... That‘ll work

No simple solutions


• Dramatic reduction in page delivery time

Reduces the need for expansive server farms

Quick and inexpensive (perhaps)

• But...

Custom data is problematic one way or the other

Complicates the application

Risk of delivering stale content

Dependency on caching usually a recipe for disaster

Page Caching


Page Caching


• Protects the data layer:

Classical vertical scaling

Far easier than scaling the database

• But...

Requires code changes

Custom data is still problematic

Risk of delivering stale content

De-caching can bring down the database

Data caching


• Caching is a divisive topic

• Let me share my experience of...

Providing a highly available cache

Providing a truly scalable cache

Providing a high performance cache

Preventing a run on the database

Ensuring fresh data resides in cache

• Remember, don‘t kill me!

This is not the only way

Let‘s get controversial...


• Network data cache

e.g. Memcache

One common architecture

Internet

LB

Cache

Server

Web Farm

DB Server(s)


• Some advantages

Only one cache to update/invalidate

Most effective way of protecting the data source

• Many disadvantages...

Single point of failure (or uncertainty when in distributed mode)

Limits scalability

Performance bottleneck

Slower

Network data cache


• Shared memory cache

e.g. Zend Data Cache, APC

A different approach

Internet

LB

Cache

Server Web Farm

DB Server(s)

X Cache

Cache

Cache


• Many advantages

Completely scalable (copy/paste architecture)

No single point of failure

Does not require TCP/IP

Very fast

• Some disadvantages...

Not the path of least resistance

More work for the data source and the developer

Your colleagues may laugh at you (but they would be wrong)

Shared memory cache


Demo...

The Great Cache Performance

Head to Head


• Taming the disadvantages

True, we need to work a little, but...

• We can use Zend Server‘s Job Queue to perform remote

cache maintenance

• We can get a list of active servers from the Web API

provided by Zend Server

• Really, we don‘t have to code much ourselves

Shared memory cache


Distributed de-caching

• With Zend Server‘s Job Queue

• ...and the job itself


• Don‘t decache, update

Regenerate the data and insert into the cache

At a minimum do this for all components of the index page

Reduces data source load

Shared memory cache on steroids


So long...

• …and thanks for all the fish.


Enhancing Scalability

With Intelligent Caching

By Eric Ritchie ([email protected])

enhancing scalability with intelligent caching

Documents

zend data cache

scalable cache

available cache

database data

high performance cache

data source

data layer

fresh data