Post on 11-Apr-2017
Building Event Driven Systems
Shiroshica KulatilakeSolutions Architect
Setting Expectations
o Today’s Enterprise Systems and how events fit in
o What is Event Driven Architecture
o Patterns for building Event Driven Systems
o Summarize
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Enterprise Systems & Events
Enterprises Today
o Distributed- Functionality is broken down into several sub systems - Located in multiple places
o Ubiquitous - Based on parties interacting through different means
o Connected- Built based on synergies- Own as well as partner systems need to interact with each
other efficiently
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Events in Enterprise Systems
o Occurrence within the context of interest o A series of events depicting one event in the real world
- e.g. A customer placing an order in a retail systemo Not all events are of interest o Most everyday events can be dealt in an asynchronous manner o Occurrence of an situation (relevant event) requires something to
react to it - to move from one state to another o For this events should be detected, situations filtered and
processes notifiedo Leads to Event Driven Architecture
Event Driven Architecture
Evolutiono SOA
- Synchronous request response systems with asynchronous message delivery
- Technically loosely coupled - Functionally tightly coupled - Mostly centralized
o Evolving into EDA- Based on message driven model for information propagation- Spatial and temporal decoupling- Analogous to the operational model of an organisation where a
series of events take place
o Suited where- Distributed environments - Higher level of autonomy is needed at unit level
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Main Components
o Event - significant happening which results in change of state from a business perspective
o Event generator- publishes eventso Event processor- consumes events and decide what to doo Event channel - medium where event lies before consumption
Principles
o Immediate information dissemination and reactive business process execution
o Fire and forget - push based mechanismo Single responsibility at practiceo Autonomous messages for the receiver to processo Higher decoupling - no need to bind to contractso Logical decoupling of functional units - not dependent and less
impact from change o Receiver driven flow control - more responsibility lies with receivers o Near real time information consistency
Advantages
o Effective data integrationo Low latency of information o High reactivenesso More accurate responseso High flexibility o Higher business agility
Generic EDA Pattern
Event Mediator Pattern
http://radar.oreilly.com/2015/02/variations-in-event-driven-architecture.html
Event Mediator Pattern
o Need to orchestrate multiple steps
o Orchestration happens through a central mediator
o Multiple steps need to happen in a certain order
o Processing will be done by separate entities which need to be invoked in many ways
o Fits scenarios which are complex, have some sort of orchestration logic and approval tasks etc as well
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Broker Pattern
http://radar.oreilly.com/2015/02/variations-in-event-driven-architecture.html
Broker Pattern
o Message flow is distributed across several processors with no orchestration
o Fits for use cases where the flow is entirely dependent on event receiving with no timing
o Once a processor is done with processing another event will be fired to the broker which will be consumed by another processor
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Components in an Event Driven System
o Process Engine
o Mediation Engine
o Message Broker
o Business Activity Monitor
o Complex Event Processor
o Business Rules Manager
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Patterns in building Event Driven Systems
Centralized Message Driven System
Sample Solution
Sample Extended Solution
Autonomous Message Driven System
Sample Solution
Sample Extended Solution
Request Rate Controlling
Guaranteed Delivery - Directly via Broker
Guaranteed Delivery - via Mediation Engine
Guaranteed Delivery - Fault Handling
Monitoring and Alerting
Keeping up with the trends
Internet of Things (IoT)
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Internet of Things (IoT)
o There exists a plethora of devices which provide data in several contexts
o This data needs to be captured in order to analyze and derive intelligence and then take actions
o Point to point integration with each device is not a possibility
o Leads to the use of Event Driven Architecture through the use of protocols which work on publish-subscribe mechanisms - e.g. MQTT and also through handling large scale event analyzing
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Internet of Things (IoT)
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Microservices Architecture
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Microservices Architecture
o Microservices promote distributed data management
o Data in microservices - Are private to a specific microservice - Use polygot persistence - Might not expose generic APIs for all possible modes of use
o However, business transactions span multiple microservices which would need accessing private data of other microservices
o Leads to the use of Event Driven Architecture where distributed data management is handled through the use of events
o Variants are event tables, transaction log mining and event sourcing which try to reduce errors relating to atomicity
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Microservices Architecture
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Reactive Architecture
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Reactive Architecture
o To achieve being reactive, systems should be designed with containment of functionality in mind so that scaling, isolation of failures and adaptable fault tolerance happens
o Microservices Architecture can achieve this
o Also, for a system to be reactive it should be able to- React to Load through scalability- React to failure through recoverability- React to user experience effectively
o The ability to react to events and act accordingly becomes the main ingredient
o Leads to designing and building systems in an Event Driven manner
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Key take aways ...
Building Event Driven Systems
o What does your enterprise system look like ?- Determine how complex or simple your system flows are- Determine how autonomous your processing units are- Determine how isolated your processing units should be
o What do you need to do with event processing ? - Identify both functional as well as operational needs
o Which pattern would suit you best ?- Select based on enterprise system characteristics and needs
o Which components do you need ?- Identity which middleware components you need to achieve the
above
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Referenceso Event Processing in Action - Opher Etzion and Peter Niblett -
Manning
o https://msdn.microsoft.com/en-us/library/dd129913.aspx
o Software Architecture Patterns - Mark Richards - Orielly
o http://radar.oreilly.com/2015/02/variations-in-event-driven-architecture.html
o http://wso2.com/whitepapers/a-reference-architecture-for-the-internet-of-things/
o https://www.nginx.com/blog/event-driven-data-management-microservices/
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