SOA Design Patterns in the Cloud

Service Oriented Architecture (SOA) is a software design approach in which an application consists of software services and  software service consumers. Some of the attributes of SOA being

• Loose Coupling
• Contracts between service provider and service consumer
• Allows co working of multiple technologies

There may be  some  confusion in the air about the applicability of SOA in a Cloud  managed environment and whether  Cloud is the next generation of SOA, however SOA as a design approach is complimentary to the attributes of Cloud and together they further strengthen the delivery of services over the network.   This articles  explains some of the design patterns of SOA and their usage in a Cloud environment.
For the sake of case study, Oracle SOA 11g Suite is  used as the SOA development platform and Amazon EC2 Suite of products is used for the Cloud platform.

While there is not a specific AMI within Amazon EC2 at this time that also host the Oracle SOA Suite, however Oracle SOA suite can very much be installed be on the  AMI that  contain Windows 2008 Server or  Red hat Enterprise  Linux .
Applicability Of SOA Design Patterns In a Cloud Platform
The following  chart  explains the various  SOA patterns, especially as applicable to Oracle SOA Suite and their  fitment to a Cloud platform.

SOA Pattern	Applicability To  Cloud Platform
Adapter Pattern : It allows to connect to multiple technologies like messaging , databases without knowing much of the internals of them. For example Database Adapter is basically to service enable databases without having to  write SQL. Oracle 11g SOA Suite supports database adapters to multiple databases.	Amazon RDS (Relational Database Services) exposed as an SOAP based interface which can be connected as a Adapter pattern using the regular Services Interface as part of Oracle SOA Suite. Amazon Simple DB is a non relational database service, which can be connected using the regular SOAP interface and can satisfy the needs of Adapter pattern in SOA. Amazon EBS and S3 based instances  can satisfy the needs of  File Adapter in a SOA.
Mediator Pattern : Mediator is the component in charge of interconnecting the other components within a composite application. Oracle SOA suite uses mediator pattern for intra composite  mediation.	With Multiple EC2 Instances can run different services like  basic compute services, storage services like EBS,  database services like  RDS, Simple DB,  it is very much possible to have a mediator  that inter connects the multiple services towards a business process realization.
Binding Pattern : The binding can be used expose the SOA composite applications over SOAP .	With Elastic IP,  Services  can be exposed to outside Cloud Consumers that will act as a Binding.
Business Process Orchestration Pattern : This pattern aims at realizing long running business process through  orchestration  of multiple individual  services. Oracle 11g Suite support BPEL Component to perform orchestration .	With various  services exposed as Services as explained above, a Business process can be orchestrated in a cloud platform much similar  in a  normal data center.
Proxy Pattern : A business service describes the end point being virtualized, its policies and interfaces. A proxy service is what the service bus exposes to service consumers and implements the virtualization logic.	With Elastic IP acting as a proxy interface to multiple virtual machines and abstracts from issues like Virtual machine failure or migration of Virtual machines, Cloud platform adapts the Proxy pattern to support virtualization.
Asynchronous Pattern : In a real world scenario Asynchronous pattern is helpful when When the response might not come back instantly from the service provider When a given request needs to be send to multiple providers or vice versa When the service consumer did not know who will provide the service When consumer and provider will not be online at the same due to geographical and time zone constraints	Amazon SQS is a distributed queue system that enables web service applications to quickly and reliably queue messages that one component in the application generates to be consumed by another component. Using Amazon SQS, you can decouple the components of an application so they run independently, with Amazon SQS easing message management between components. Any component of a distributed application can store any type of data in a fail-safe queue. Any other component can then later receive the data programmatically using the SQS API.

Summary
With SOA is fundamentally a loosely coupled computing paradigm, with the following attributes :

• Loose Coupling
• Discoverability
• Location Transparency

The Cloud Platform  is a ideal platform for implementing  SOA based Business Process Realization and the above mentioned supporting Services in Amazon EC2 will help to realize the Same.

A similar comparison is also possible in the Windows Azure platform with the support from Microsoft framework.  So as we see,   Cloud Platform further compliments to the benefits of SOA platform.