Architecting an Highly Available and Scalable WordPress Site in AWS

Architecting an Highly Available
and Scalable WordPress Site in
AWS

Harish11g.aws@gmail.com
http://harish11g.blogspot.com

Why this presentation ?

• WordPress is used by over 14.7% of Alexa Internet's
"top 1 million" websites
• As of August 2011 WordPress powers 22% of all
new websites
• As of December 2011, version 3.0 had been
downloaded over 65 million times
• Provide some architectural insights to build Highly
Scalable and Available WordPress sites in AWS
• Help startups and companies who are new to AWS-
WordPress with some blueprints

WordPress Architecture Requirements in
AWS
• Ability to Serve millions of Pages per day
• Ability to scale out/down dynamically depending
upon traffic
• Ability to perform well even with scaling demands
• Should be Highly available without Single Points of
Failure
• Automated Operations – Backup and Monitoring
• Cost effective

Why AWS is better for WordPress Scaling?

• AWS provides flexibility to Scale up and Scale out
• AWS provides Building block services which is
inherently robust and fault tolerant
• AWS provides full range of options from CDN , OS
flavors , Storage Pool , Database , Load Balancers ,
Monitoring etc
• Pay as you go – Save cost by leveraging Auto Scaled
WordPress EC2 instances
• We can start small and grow big in AWS

AWS Building Blocks used in this WordPress
Architecture

Some AWS building blocks

Amazon Amazon Route53 for managing and answering DNS queries
Route 53

Amazon Elastic Load Balancer for load balancing HTTP/S
requests to WordPress Instances

RDS MySQL Database Server for storing the WordPress content

Simple Storage Service (S3) for storing the WordPress
S3
application assets , snapshots and log files

Amazon
Amazon CloudFront CDN for delivering the application static
CloudFront assets from nearest edge locations

Amazon Amazon CloudWatch for monitoring and sending SNS alerts
CloudWatch

Highly Scalable Architecture for WordPress
application

Admin
Amazon
AZ : Amazon Amazon CloudFront
Availability Zones Route 53

AWS Region 1 Static Data

SSH/SFTP Elastic
Load S3
Balancer
Amazon
CloudWatch
Az-1 Az-2
Alarms Auto Scaled
WordPress EC2
WordPress instances
Management Server

Amazon SNS
Notifications
Az-1 Az-2

Az-1 Az-2 Standby

RDS Master
Read Replica

Backups and
Log files File Storage Pool Database Layer Database Layer

Brief about the Architecture

• Multi- Tiered Architecture
• Load balancing tier
• Separate WordPress Management and Instance nodes
• Auto Scaled WordPress EC2 instance nodes
• MySQL M-S database with additional Read Slaves
• S3 + CDN for content delivery
• Monitoring , Backups , Sys alerts

Architectural Tiers Explanation

Now let us see the tiers in detail !!

Load Balancing with Amazon ELB

• Amazon Elastic Load Balancing will Load balance the
http requests to WordPress EC2 instances
• ELB will direct the requests to WordPress EC2 across
Multiple Availability Zones ( for HA)
• Health check , LB algorithms and SSL termination
will be done by the Load Balancer
• Amazon Elastic Load Balancing can keep expanding
its capacity automatically depending upon the
traffic

Load Balancing with Amazon ELB

• Amazon ELB works with Route 53 and Auto Scaling
seamlessly
• Amazon ELB is priced @“ Pay for use” model
• Amazon ELB is a managed service , so
• NO Maintenance headaches
• NO SW/HW upgrades
• NO Capacity planning
• NO manual intervention for expansion

How scalable is this architecture ?

Scalability and Elasticity

• Scalability and Elasticity is built in most of the layers
in this architecture
• WordPress EC2 instances can be scaled out and
down depending upon the traffic
• We can expand the number of WordPress EC2 instances from 1 to
100+ automatically during load peaks
• We can reduce the number of WordPress EC2 instances from 100+
to 1 automatically during valleys
• Can serve millions of pages with ease
• Pay only for the EC2 instance hours used


• Read Scalability is built in the Database layer with
RDS Read Replicas
• New RDS Read Replicas can be added / removed
with ease
• Tips:
• During Campaigns alone we can run more RDS Read Replicas
• Not more than max 5 RDS Read replicas are recommended
• Keep Read Replica’s and RDS Master same EC2 size for better
performance


• Clustered + Distributed File System of the Storage
pool layer can be manually scaled in case needed
• Minimum 2 EC2 Large instances should be used for
Storage Pool Layer ( for HA and better IO)
• Design the Storage Pool Layer with HA (very critical)
• AWS building blocks like S3 , CloudFront ,
CloudWatch , SNS used in this architecture are
inherently designed for scalability

How High Availability and Fault tolerance is
built in this Architecture ?

High Availability

• HA @ WordPress Layer
• Multiple WordPress EC2 instances avoid single point of
failure
• WordPress EC2 instances are launched across multiple –
AZ’s inside a region for High Availability
• HA @ DB Layer
• RDS MySQL Master and Standby are launched in 2
different availability zones for High Availability
• RDS Read Replicas are created in Multiple –AZ’s

High Availability

• HA @ Storage Pool Layer
• Two EC2 instances used for Storage Pool Layer
• Storage Pool is setup in replicated mode for High
Availability
• AWS building blocks like S3 , Cloud Front ,
CloudWatch , ELB , SNS ,EBS used in this
architecture are inherently designed for Fault
tolerance and HA

How the Database Tier is Architected ?

Database layer

• RDS Master and Standby provide High availability
• RDS Read Replicas provide Read performance
• HyperDB plugin is configured to use multiple
endpoints like RDS master and RDS read replicas in
this architecture
• DB security groups will allow DB access only to
WordPress EC2 instances
• Periodic Dumps , Snapshots and Point in time
recovery is possible in this architecture

What performance aspects are taken care in
this Architecture ?

Performance

• APC (or) Xcache plugin can be used for PHP opscode
caching
• W3TotalCache+CloudFront (or)
BatCache+Memcached can be used for Page
caching
• Multiple RDS Read Replicas for Read performance
• RDS Master and Read Replicas are separated to get
independent write and read performance
• Amazon ELB + Auto Scaling improves the overall Site
performance when the load increases

Content Delivery

• Amazon CloudFront will be the Content Delivery
Network (CDN)
• W3TotalCache plugin will be configured to use
Amazon CloudFront for enhanced performance and
reduced latency
• Static assets , templates , themes , images etc will
delivered from the nearest edge locations of the
CDN

Deployment

• Distributed File Storage Pool is configured between
WordPress Management and Content instances
• WordPress Management and Content instances
share the common storage pool for files and plugins
• Deployment of files and plugins will happen
through the WordPress management node
• Files and plugins will be immediately available for
use in the auto scaled WordPress EC2 instances

Monitoring

• Amazon CloudWatch will monitor the CPU and
Network utilization of the entire setup
• Amazon CloudWatch alarms configured with
Amazon SNS provides Email/SMS alerts to System
Administrators

Backup

• Custom ops scripts will backup the necessary files
from Storage pool to S3 periodically
• S3 can be configured to remove old backups
automatically
• RDS MySQL is configured to take periodic data
dumps and DB snapshots
• RDS layer can be recovered point in time from the
backups

Security

• Suitably hardened OS for WordPress Mgmt and
WordPress instances
• Firewall (or) AWS security groups configured
between all the layers in the architecture
• SFTP/FTP access only to the WordPress
management node
• AWS IAM policies to manage user account access
• Install WordPress Security plugins

Advantages

• Highly Available and Scalable architecture
• Can elastically scale out to serve millions of hits in
a day
• Can grow with load demands in future
• Usage of inherently fault tolerant AWS building
blocks adds Stability
• High performance using CDN and suitable cache
plugins
• Monitoring , Backup and Recovery is built in
• Pay for use

Disadvantages

• Complex to setup and maintain
• Will not be ideal for smaller sites that do not need
scale
• Will not be cost efficient for sites that have less
traffic

Key Points to Remember

• Log files generated in WordPress EC2 instances have
to rotated
• Use Amazon EBS for Storage Pool and WordPress
EC2 instances
• Start with EC2 m1.Large Instances for the storage
pool and WordPress instances
• More Memory – Better Performance for DB
• Start with RDS Large for Master
• Keep RDS Master and RDS Read Replica’s in same size to
improve read performance


• RDS MySQL supports only Innodb engine
• Separate the WordPress Management and
WordPress Content instances for scalability
• Do not Scale out/down rapidly in a hour, it will cost
more in AWS
• Combine AWS On-Demand and Reserved Instance
pricing to get more savings per month


• Amazon Availability Zones(AZ’s) are distinct physical
locations with Independent power , cooling
,network and security having Low latency network
connectivity between them inside the same region
• Leverage them in WordPress , Storage Pool and DB layers
for HA as mentioned in the architecture

How do I setup Scalable WordPress
architecture on AWS?

Leave it to the experts , we will
handle this

Cloud Architecture Consulting
Cloud Application Development
Cloud Migration & Implementation
Cloud Adoption Strategy

“Let's get the job done”

Contact

Harish11g.aws@gmail.com
http://in.linkedin.com/in/harishganesan
www.twitter.com/harish11g
http://harish11g.blogspot.com

Architecting an Highly Available and Scalable WordPress Site in AWS

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