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Introduction to event based microservices
- 2. Grigoriadis Grigoris Co-Founder &Software Architect @ Microservices enthusiast !
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- 4. What we willcover ● What is Monolithic Architecture ● What is Microservices Architecture ● Pros/Cons ● Moving to Event Based Microservices
- 5. Monolithic Architecture DB UI Module Functioncalls Server ● Building block is the code modules ● Modules communicate with each other using function calls ● System is deployed and run as a single OS process ● A Database is used in order to store the system state, usually a relational database
- 6. Microservice Architecture -Bare Minimum UI Microservice HTTP calls API Gateway ● Building block is the microservices ● Services communicate with each other via a lightweight interoperable communication protocol, usually HTTP ● Each service MUST have its own database ● An API Gateway provides a unified API for our system
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- 8. Architectural Factors Scalability MaintainabilityEvolvability Fault Tolerance How well the system handles a growing amount of data/requests? Is the system simple and easy to understand? Is the system design in such a way that can evolve along with the product requirements and the changing ecosystem? When part of the system fails does it fail completely? Horizontal
- 9. Scalability Load Balancer API GatewayAPI Gateway Load Balancer ● The entire system must be scaled ● Different modules might have different resource requirements ● Services can be deployed on different machines ● Services can be scaled independently Monolithic Microservices ● Databases must be scaled along with microservices ● Service discovery ● Easier to scale
- 10. Maintainability Monolithic Microservices ● Easier todebug ● Each service is small in code size and easier to understand ● Easier to work with different teams ● Boundaries between modules tend to break ● Code size becomes intimidating ● A change can impact the whole system ● Communication between services might become complicated and difficult to follow ● Business logic might leak to API Gateway and can become complex API Gateway
- 11. Evolvability Monolithic Microservices ● Microservices canbe rewritten individually in different language using different database ● Changes in infrastructure can be applied gradually to each microservice ● Refactoring in Database is easier since each database is governed by 1 team ● Any change, such language change, db change etc. must be applied to the whole application ● Refactoring database requires coordination between multiple teams t t
- 12. Fault Tolerance Monolithic Microservices ● Partof the system will continue to work even if some services are not working ● If a module has a memory leak or malfunctions the whole system might stop working
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- 14. Microservice Architecture -Event Based ● An event is a fact, something that has already happened and cannot change ● Every state change must generate an event ● Events should NOT be overly generic (e.g. OrderUpdated), prefer more specific events like OrderStatusChanged or even better OrderDispatched etc. ● Events should contain only data relevant to the event. Event +entityId: string +time: DateTime +type: string
- 15. Microservice Architecture -Event Based UI Microservice Through Broker (Pub-Sub) API Gateway Broker ● Microservices publish events in the broker and consume events that are of interest in order to update their databases ● Services do not communicate with each other to exchange information, they duplicate the data they need from events ● System has Eventual Consistency ● Better performance ● Fault tolerant ● Service discovery only used by API Gateway ● Difficult to design ● API Gateway is still complex
- 16. Microservice Architecture -CQRS UI Command Microservices Through Broker API Gateway Broker Query Microservices ● Command microservices update the state of our system and publish events ● Query microservices deal with keeping the data in a schema appropriate for the UI ● Better performance ● Decoupled read from write schema ● API Gateway does not need to compose calls ● Still need to commit to multiple middleware
- 17. Microservice Architecture -Event Sourcing UI Through Event Store API Gateway Event Store Command Microservices Query Microservices ● All state changes in our system are represented as events. ● All events are persisted in an event store. ● Each microservice creates its state from the events in the event store and keeps a snapshot for faster access. ● Better performance ● Each microservice can recreate its state ● Difficult to implement
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