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When we have to use an Event Driven Architecture?Initially, Current Practices and Future
What we will cover hereWhat is the Event Driven Apps?When is the Event Driven Architecture was
started?What is the Benefit?When we have to use?What is the Implementation in the real
world?What is the trend?
What is the Event Driven Apps?What is an Event?What is in an Event?What is the Reaction when an Event fires?
Ask Wiki!An event is a notable thing that happens
inside or outside your businessThe term event is often used interchangeably
to refer to both the specification (definition) of the event, and each individual occurrence (instance) of the event
Each event occurrence has an event header and event body as the delivered information
How’s an Event being consumed?It should be Published!And then Fired! And someone must Listen!And he /she will give some Reaction!Or, just ignore it!...
Simply, EDA will be as
Event Listener
Event Action
The Problem on Event TriggerTriggered by Predictable Events
Triggered by Un Predictable EventsRequired Active Listeners
The Problem on the ActionSynchronous Action
Asynchronous Action
When is the Event Driven Architecture was started?Four years from now, "mere mortals" will
begin to adopt an event-driven architecture (EDA) for the sort of complex event processing that has been attempted only by software gurus building operating systems or systems management tools, and sophisticated developers at financial institutions. (Roy Schulte, an analyst at Stamford, Conn.-based Gartner - 2003)
What is the Benefit?ScalableReaction basedStagedStaged + Reaction =
When we have to use?Best used for Asynchronous Flows of Work
and InformationWhen you need a Fast Responsive in front,
but Asynchronous process in the backgroundFire and Forget handling
Samples:The Web Server
What else? (Quiz)
ReplicationSchedulerReportingSynchronizationMessenger
Use these following key words:
Then add with word “Engine“
What is the Implementation in the real world?SOA based implementationMessaging based solutionAutomation solutionWorkflow solution
Sample of Messaging Solution
Sample of Workflow
Sample of Complex Workflow
Existing SampleNatPOS WindMills using SEDA
Implementation
What is the trend?Workflow enabled applicationFrom Enterprise Level to Single Instance
Application
To Single Instance: WWFSequential WorkflowState Machine WorkflowRule Driven Activities
Rules-driven Activities
Step2
Step1Rule1
Rule2
DataRules + data statedrive processing order
•Data-driven•Simple Conditions, complex Policies •Constrained Activity Group
State Machine Workflow
State2
State1Event
Event
External events drive processingorder
•Reactive, event-driven•Skip/re-work, exception handling•Graph metaphor
Sequential WorkflowStep1
Step2
Sequentialstructure prescribesprocessing order
•Prescriptive, formal•Automation scenarios•Flowchart metaphor
References:4 Years prediction on SOA implementation - Gartner
Event Driven Architecture – InfoQ articleMicrosoft .NET Framework 3.0, 3.5, WWF
NatPOS workflow engine - WindMills