Event driven architecture
- 1. EVENT DRIVEN ARCHITECTURE VINOD WILSON – ARCHITECT – CRESTRON ELECTRONICS
- 2. WHAT IS IN AN EVENT? An event is a notable thing that happens inside or outside your business. An event (business or system) may signify a problem or impending problem, an opportunity, a threshold, or a deviation.
- 3. SPECIFICATION AND OCCURRENCE The term event is often used interchangeably to refer to both the specification (definition) of the event, and each individual occurrence (instance) of the event.
- 4. WHAT IS IN AN EVENT? 1. Event specification ID 2. Event Type 3. Event Name 4. Event Timestamp 5. Event Occurrence Number 6. Event Creator HeaderBody
- 5. EVENT TYPES • ORDINARY EVENT • Example: Regular Temperature information • NOTABLE EVENT • Example: Temperature reaching above the threshold limit of 40 degrees
- 6. EVENT PROCESSING STYLES • SIMPLE EVENT PROCESSING • In simple event processing, a notable event happens, initiating downstream action(s) • STREAM EVENT PROCESSING • In stream event processing, both ordinary and notable events happen • COMPLEX EVENT PROCESSING • Complex event processing (CEP) deals with evaluating a confluence of events and then taking action • The events (notable or ordinary) may cross event types and occur over a long period of time. • CEP requires the employment of sophisticated event interpreters, event pattern definition and matching, and correlation techniques • CEP is commonly used to detect and respond to business anomalies, threats, and opportunities.
- 7. EVENT GENERATORS Every event is generated from a source Sources 1. Application 2. Data Store 3. Service 4. Business process 5. Transmitter 6. Sensor 7. Collaboration Tool
- 8. EVENT PREPROCESSOR • The processor can act as ROUTER or FILTER • An ordinary event may be evaluated for notability by an event preprocessor (router, filter), resulting in the generation of a new notable event.
- 9. EVENT CHANNEL • The event channel, typically a messaging backbone, transports standard formatted events between event generators, event processing engines, and downstream subscribers.
- 10. EVENT PROCESSING • In the event processing layer, upon receipt, events are evaluated against event processing rules, and actions are initiated • The event processing rules and actions are defined in accordance to the needs of the interested parties, not of the event generators. ACTIONS 1. PUBLISH 2. NOTIFY 3. INVOKE SERVICE 4. START BUSINESS PROCESS 5. CAPTURE 6. GENERATE EVENT publishing the event out to a subscription hub Directly notifying humans or systems
- 11. EVENT REACTIONS • Reactions to an event Reactions 1. Automated application responses 2. Automated notifications sent to either applications or people 3. Human reactions
- 12. MESSAGE FLOW
- 13. EVENT STREAM PROCESSING • Event stream processing involves event processors receiving a number of signals from event producers (via the event listeners) but only reacting when certain criteria are met
- 14. COMPLEX EVENT PROCESSING - REVERSING • Determine event sequence that created the desired event • CEP == AI (Artificial Intelligence)
- 15. EDA • sensitive, responsive, and teachable
- 16. LOOSE COUPLING • Loose coupling is the measurement of two fundamentals • Preconception • The amount of knowledge, prejudice, or fixed idea that a piece of software has about another piece of software • Maintainability (Changeability) • The level of rework required by all participants when one integrated component changes
- 17. ADAPTERS
- 18. EVENT FLOW
- 20. SITUATION • A situation is an event occurrence that might require a reaction • One of the main themes in event processing is the detection and reporting of situations so that they can be reacted to
- 21. EXAMPLE OF EVENT PROCESSING Event Generator Event Generator Event Generator Event Processor Event 1 Event 2 Event 3 If certain combinations are measurements are detected, then raise alert
- 22. ABSENCE PATTERN OR NON-EVENT • The fact that an event did not occur is one of the most common event processing patterns, called the absence pattern
- 23. CATEGORIES OF EVENT PROCESSING APPLICATIONS
- 24. EVENT PROCESSING AND ITS RELATIONSHIP TO THE REAL WORLD • Deterministic— There is an exact mapping between a situation in the real world and its representation in the event processing system. • Approximate— The event processing system provides an approximation to real world events.
- 25. STATELESS EVENT PROCESSING • An event processing agent is said to be stateless if the way it processes one event does not influence the way it processes any subsequent events • Filtering, routing and logging are all examples of stateless event processing
- 26. STATEFUL EVENT PROCESSING • An event processing agent is said to be stateful if the way it processes events is influenced by more than one input event • An incoming event may be split into multiple events, each containing a subset of the information from the original event • A stream of multiple incoming events may be aggregated to produce a stream of derived events. The derived events are typically computed from more than one event from the input stream • Two streams of incoming events may be composed to produce a stream of derived events
- 27. EVENTS AND MESSAGES • The difference here is that the event is the entity that records information about the event occurrence, whereas the message is the mechanism used to exchange that information
- 28. WHAT IS AN EVENT STREAM? • An event stream (or stream) is a set of associated events. It is often a temporally totally ordered set (that is to say, there is a well-defined timestamp-based order to the events in the stream) • Homogeneous event stream • A stream in which all the events must be of the same type • Heterogeneous event stream • A stream in which the events may be of different types • The stream concept can be particularly useful in applications that involve time series events, such as the periodic reading of a sensor or periodic quotes of a stock price
- 29. WINDOW • Stateful agents can be defined so that they operate only on subsets of the input events that they receive • In stream processing terminology, such a subset is often referred to as a window into the stream
- 30. SEVEN FUNDAMENTAL BUILDING BLOCKS OF EVENT PROCESSING
- 32. CHANNEL-BASED EVENT DISTRIBUTION • It could be an intermediary service or other piece of software (sometimes called a broker). • It could be implemented using a multicast protocol, such as IP Multicast. • It could be implemented using message-oriented middleware (MOM), such as a Java Message Service (JMS) provider.
- 33. AN EVENT TYPE SHOULD ANSWER • What happened? • When did it happen? • What other information is associated with this happening?
- 34. LOGICAL STRUCTURE OF AN EVENT INSTANCE
- 35. HEADER ATTRIBUTES • Attributes whose values are generally set by the application: occurrence time, event certainty, and event annotation • Attributes whose values can be system generated: event identity, detection time, and event source
- 36. Thank you