JavaEE workshop #9

Kuba Hejda

(Strategy pattern, Microservices architecture, Spring cloud basics)

Previous workshop

• Web Services

• Swagger/OpenApi

Contents

• IDEA shortcut: refactoring - Ctrl+Alt+Shift+T
• Strategy pattern
• Monolith vs Microservices architecture
• Spring cloud

IDEA shortcut

• IDEA shortcut:
  • within a class press Ctrl+Alt+Shift+T
  • refactoring

Strategy pattern

• we need a different behavior based on the subject type but under the same interface
• example

Application achitecture

• Different approaches for different use-cases
• The decision can affect the success of the whole project
• Not a general rule
• Often based on clients requirements, runtime abilities and the budget

Application achitecture

Application achitecture

• Monolith
  • advantages
    • easier to maintain, learn and develop on smaller projects
    • easier deployment and integration
    • faster interoperability between modules
  • disadvantages
    • on larger projects can be a mess, harder to test
    • unable to scale only the module which is under load
    • on larger projects a lot on conflicts especially in the beginning of the implementation

Application achitecture

• Microservices
  • advantages
    • on larger project each part of the development team can focus on its own service
    • great for horizontal scaling, balancing of the load, out-of-the box prepared to run in cloud
  • disadvantages
    • higher demands on architecture and preparation
    • needs more to work properly (load balancing, routing, higher resources), especially in the early stage of the project

Spring cloud

• provides tools for developers to quickly build some of the common patterns in distributed systems (e.g. configuration management, service discovery, circuit breakers, intelligent routing, micro-proxy, control bus, one-time tokens, global locks, leadership election, distributed sessions, cluster state).

• Distributed/versioned configuration, Service registration and discovery, Routing, Service-to-service calls, Load balancing, Circuit Breakers, Global locks, Leadership election and cluster state, Distributed messaging

Spring cloud

Service registry

• In the cloud, applications can’t always know the exact location of other services.
• A service registry, such as Netflix Eureka, or a sidecar solution, such as HashiCorp Consul, can help. Spring Cloud provides DiscoveryClient implementations for popular registries such as Eureka, Consul, Zookeeper, and even Kubernetes' built-in system.
• There’s also a Spring Cloud Load Balancer to help  distribute the load carefully among  service instances.

API Gateway

• With so many clients and servers in play, it’s often helpful to include an API gateway in your cloud architecture.

• A gateway can take care of securing and routing messages, hiding services, throttling load, and many other useful things.

• Spring Cloud Gateway gives a precise control of the API layer, integrating Spring Cloud service discovery and client-side load-balancing solutions to simplify configuration and maintenance.

   

Cloud configuration

• Many services need different configurations which cannot be stored inside cloud apps

• The configuration has to be flexible enough to cope with multiple applications, environments, and service instances, as well as deal with dynamic changes without downtime

• SpringCloudConfig offers solution to these problems, can serve config from the git or filesystem

Tracing

• Debugging distributed applications can be complex and take a long time.

• For any given failure, you might need to piece together traces of information from several independent services.

• Spring Cloud Sleuth can instrument applications in a predictable and repeatable way. And when used in conjunction with Zipkin, you can zero in on any latency problems you might have.

Q&A