Sw architectures 2018 on microservices and eda
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This document discusses microservices and event-driven architectures. It provides an example of a "smart road" system using these approaches. Events are used to communicate between isolated microservices to handle tasks like vehicle identification, traffic rate calculation, billing, and detecting stolen vehicles. The document also discusses using events to handle consistency requirements when processing salary increases across budget-checking and other microservices. Events allow microservices to remain independent while coping with global consistency needs through approaches like compensating transactions triggered by event notifications.
Sw architectures 2018 on microservices and eda
- 1. Speaker: Opher EtzionOn Microservices and Event Driven Architectures The 5th Israeli Conference on Software Architectures Opher Etzion
- 3. Event Driven Architecture Event driven architecture: asynchronous, decoupled; each component is autonomic.
- 4. 4 Complementary Architectures Microservices stand for component architecture; Event driven deals with the interaction among components
- 5. 5 Simple case – the smart road The road fare for each segment is determined by the volume of traffic in that segment in the previous time window Cameras in each segments identifies the cars for: counting, direct billing, tracking stolen cars
- 6. 6 Simple case – The smart road Identify vehicle Calculate segment rate Bill driver Detect payment avoider Detect stolen car Event broker No mutual consistency required
- 7. 7 Simple case – The smart road Identify vehicle Calculate segment rate Bill driver Detect payment avoider Detect stolen car Event broker Identify Vehicle emits events with segment and vehicle id. Calculate Segment rate, Bill driver, detect payment avoider and Detect stolen car subscribe to it
- 8. 8 Simple case – The smart road Identify vehicle Calculate segment rate Bill driver Detect payment avoider Detect stolen car Event broker Calculate segment rate emits at the end of every time window event with new rates. Bill driver subscribes to it.
- 9. 9 Simple case – The smart road Identify vehicle Calculate segment rate Bill driver Detect payment avoider Detect stolen car Event broker Detect stolen car and detect payment avoider emit events that the highway security subscribe to, in order to stop vehicle.
- 10. 10 Constrained case – Salary Increase Salary determination process results in salary increase. There are two integrity constraints: 1. Department total salaries and other expenses cannot exceed the budget 2.A manager salary must not be more than the equivalent to 25 salaries of the lowest paid subordinate (direct or indirect)
- 11. 11 Simple connection – the smart road Increase Salary Handle Budget Check manager constraint Event broker Mutual consistency requirements exist
- 12. 12 Consistency in the monolithic case One transaction – either all commit or all abort. Using ACP (Atomic Commitment Protocol) such as: 2PC, 3PC In the microservices case – breaks the independence if applied
- 13. 13 Consistency 101 Consistency modes: Fully consistent – all time consistency Quasi consistent – eventual consistency Loosely consistent – may give up consistency
- 14. 14 Consistency 101 Stabilizers: Restrict : Always abort inconsistencies Nullify: Nullify problematic attributes Repair Transaction: Typically minimal repair that satisfies all constraints Cascade: Repair existing data to satisfy constraints Forgive: Making it loosely consistent
- 15. 15 Back to the salary increase story Increase Salary Handle Budget Check manager constraint Event broker Always use eventual consistency. Consistency may be violated temporarily
- 16. 16 Back to the salary increase story Increase Salary Handle Budget Check manager constraint Event broker The – commit or abort decision (or quasi commit if supported) is emitted as event and may trigger compensating transaction in other microservice
- 17. 17 Back to the salary increase story Increase Salary Handle Budget Check manager constraint Event broker Example: Budget violation occurred. If RESTRICT applies - budget update aborts; event emitted to broker, published to Increase Salary and triggers compensating transaction to undo the salary increase
- 18. 18 Back to the salary increase story Increase Salary Handle Budget Check manager constraint Event broker Example: Budget violation occurred. If REPAIR TRANSACTION applies - Budget update emits an event with maximum salary increase allowed, Increase Salary subscribes to it and issues a compensating transaction to modify the increase
- 19. 19 Back to the salary increase story Increase Salary Handle Budget Check manager constraint Event broker Example: Budget violation occurred. If Cascade applies - Handle budget increases the budget in the minimal amount that satisfies the constraint
- 20. 20 Back to the salary increase story Increase Salary Handle Budget Check manager constraint Event broker Example: Budget violation occurred. If Forgive applies - The consistency violation is ignored.
- 21. 21 Summary Microservices and EDA co-exist and complement each other EDA serves as a vehicle to communicate among microservices without harming their isolation EDA is Vital to cope with global consistency requirements in a way that each microservice is isolated, with no global coordination mechanism or global protocol.
- 22. 22 My long term work is aimed to take advantage of the power of events to make a better world