Tuesday, March 5, 2013

Event Driven Architecture(EDA) and Event Driven SOA

Event: An event is a notable thing that happens inside or outside your business.

An event (business or system) may signify
1. a problem
2. impending problem
3. an opportunity
4. a threshold or
5. a deviation.

Specification and Occurrence: Event refers to both specification(definition) and individual occurrence(instance).

Event in business terms: An event to be meaningful down stream subscribers(human or automated) it is imperative that event(name and body) is specified in business terms not data or application.

Event info should contain:

Header:
 specification ID
 event type
 event name
 event timestamp
 event occurence number
 event creator

Body: should specify what happened

EDA: Notable thing happening in or out of business/system, which goes immediately to interested parties. Interested parties can evaluate and optionally take action(invoke a service, trigger a business process).

1. provide agility and flexibility to business.
2. customer and business works in real time
3. passive request/reply to proactive publish/subscribe
4. active info sharing


EDA principles:

1. decoupled
2. reusability
3. Real time notifications
4. publish/subscribe
5. immediate response
6. freedom to act
7. statelessness


Extreme loose coupling

Event processing styles:

1. Simple event processing: Simple event processing is commonly used to drive the real-time flow of
work—taking lag time and cost out of a business.

2. Stream event processing: Stream event processing is commonly used to drive the real-time flow of information in and around the enterprise––enabling in time decision making.

3. Complex event processing: CEP is commonly used to detect and respond to business anomalies, threats, and opportunities.

Event flow Layers:
1.   Event generators
2.   Event channel
3.   Event processing
4.   Downstream event driven activity


Event-driven architecture implementation components:
1. Event metadata: Event metadata includes event specifications and event processing rules. Event specifications must be made available to event generators, event format     transformers, event processing engines, and subscribers.
2. Event processing: The cores of event processing are the engine and the event occurrence data.simple events engines are usually in house developed. CEP is used for trend analysis and audit.
3. Enterprise Integration: Some of the service are required from integration services are: event pre-processing (filters, routes,and transformations), event channel transport,service invocation, business process invocation,publication and subscription, and enterprise information access.
4. Sources and Targets:
5. Event Tooling: required for event specifications and processing rules, and to manage subscriptions. Event management provides admin and monitoring.



Ref:

https://gupea.ub.gu.se/bitstream/2077/23491/1/gupea_2077_23491_1.pdf

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