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Microservices With Spring Boot and Spring Cloud
Netflix
Capgemini APPS Evolve! Summit 2016
Bad Soden, 3rd of March 2016
Krzysztof Sobkowiak ( )
The Apache Software Foundation Member
Senior Solution Architect at Capgemini
@ksobkowiak

Outline
Domain Architecture
Basic Technologies
Service Discovery
Load Balancing
Communication
Resilience

Architecture Considerations
Separate data storages
Lots of communication
Bounded Context
Don’t modularize microservices by data

HSQL Database
In memory database
Not really suited for production use
Keeps the example application easy

Spring Data JPA
Provides support to build repositories based on Spring and JPA
Support for Querydsl predicates and thus type-safe JPA queries
Pagination support, dynamic query execution, ability to integrate custom data access code
p u b l i c i n t e r f a c e P e r s o n R e p o s i t o r y e x t e n d s P a g i n g A n d S o r t i n g R e p o s i t o r y {
L i s t f i n d B y L a s t N a m e ( @ P a r a m ( " n a m e " ) S t r i n g n a m e ) ;
}

Spring Data REST
Provides the domain objects with little effort via REST
Can hide certain data elements
Can be con gured exibly
Tight coupling between the internal model and the interface can be decoupled
@ R e p o s i t o r y R e s t R e s o u r c e ( c o l l e c t i o n R e s o u r c e R e l = " p e o p l e " , p a t h = " p e o p l e " )
p u b l i c i n t e r f a c e P e r s o n R e p o s i t o r y e x t e n d s P a g i n g A n d S o r t i n g R e p o s i t o r y {
L i s t f i n d B y L a s t N a m e ( @ P a r a m ( " n a m e " ) S t r i n g n a m e ) ;
}

Spring Boot
It can be pretty small…
Prede ned packages/starters available
Can generate WAR or JAR le
@ R e s t C o n t r o l l e r
@ S p r i n g B o o t A p p l i c a t i o n
p u b l i c c l a s s C o n t r o l l e r A n d M a i n {
@ R e q u e s t M a p p i n g ( " / " )
p u b l i c S t r i n g h e l l o ( ) {
r e t u r n " h e l l o " ;
}
p u b l i c s t a t i c v o i d m a i n ( S t r i n g [ ] a r g s ) {
S p r i n g A p p l i c a t i o n . r u n (
C o n t r o l l e r A n d M a i n . c l a s s , a r g s ) ;
}
}

Writing a single service is nice…

…but no microservice is an island

Challenges of Distributed Systems
Con guration management
Service registration & discovery
Routing & balancing
Fault tolerance (Circuit Breakers!)
Monitoring

Spring Cloud Components
Security - supports the implementation of security mechanisms
Con g - centralizes and dynamically adjusts the con guration
Bus - sends dynamic con guration changes for Spring Cloud Con g
Sleuth - distributed tracing with tools like Zipkin or Htrace
Zookeeper - supports Apache Zookeeper
Consult - facilitates Services Discovery using Consul
Cluster - implements leader election and stateful patterns using technologies like Zookeeper or Consul
Stream - supports messaging using Redis, Rabbit or Kafka

Spring Cloud Netflix
Zuul - routing
Ribbon - Load Balancer.
Hystrix - resilience in Microservices.
Turbine - can consolidate monitoring data from different Hystrix servers.
Feign - option for an easier implementation of REST clients
Eureka - Service Discovery

Why Eureka?
REST based service registry
Supports replication
Caches on the client
Resilient
Fast, but not consistent
Foundation for other services

Eureka Client
Registers automatically with the Eureka server under a de ned name
Can access other Microservices
Integrates Load Balancing with Ribbon using
DiscoveryClient, FeignClient
Eureka aware RestTemplate(sample later)
@EnableDiscoveryClientor @EnableEurekaClient
Dependency to spring-cloud-starter-eureka
e u r e k a . c l i e n t . s e r v i c e U r l . d e f a u l t Z o n e = h t t p : / / e u r e k a : 8 7 6 1 / e u r e k a /
e u r e k a . i n s t a n c e . l e a s e R e n e w a l I n t e r v a l I n S e c o n d s = 5
s p r i n g . a p p l i c a t i o n . n a m e = c a t a l o g
e u r e k a . i n s t a n c e . m e t a d a t a M a p . i n s t a n c e I d = c a t a l o g : $ { r a n d o m . v a l u e }
e u r e k a . i n s t a n c e . p r e f e r I p A d d r e s s = t r u e

Eureka Server
@EnableEurekaServer
Dependency to cloud-starter-eureka-server
@ E n a b l e E u r e k a S e r v e r
@ E n a b l e A u t o C o n f i g u r a t i o n
p u b l i c c l a s s E u r e k a A p p l i c a t i o n {
p u b l i c s t a t i c v o i d m a i n ( S t r i n g [ ] a r g s ) {
S p r i n g A p p l i c a t i o n . r u n ( E u r e k a A p p l i c a t i o n . c l a s s , a r g s ) ;
}
}

Ribbon
Decentralized, client side Load Balancing
No bottle neck
Resilient
Registration information might be inconsistent

RestTemplate& Load Balancing
@RibbonClient
Dependency to spring-cloud-starter-ribbon
@ R i b b o n C l i e n t ( n a m e = " r i b b o n A p p " )
. . . / / L e f t o u t o t h e r S p r i n g C l o u d / B o o t A n n o t a t i o n s
p u b l i c c l a s s R i b b o n A p p {
@ A u t o w i r e d
p r i v a t e R e s t T e m p l a t e r e s t T e m p l a t e ;
p u b l i c v o i d c a l l M i c r o s e r v i c e ( ) {
S t o r e s t o r e = r e s t T e m p l a t e . g e t F o r O b j e c t ( " h t t p : / / s t o r e s / s t o r e / 1 " , S t o r e . c l a s s ) ;
}
}

Zuul Routing
One URL to outside
Internal many microservices
Maps route to server registered on Eureka, e.g.
/customer/**to CUSTOMER
Allows to internally change the structure of the
Microservices
REST or HTML gui
@EnableZuulProxy, dependency to spring-cloud-starter-zuul
Alternatively @EnableZuulServer- no routing, uses lters

Eureka, Zuul & Ribbon Interactions

Microservices can deal with the failure of other Microservices
Even if a called Microservice is not available, they will still work

Hystrix
Enables resilient applications
Call in other thread
Won’t block request handler
Can implement timeout

Circuit Breaker with Hystrix
Circuit open after certain number (error threshold) of failed calls
If open, calls not directed to called system
After con gured window circuit closes

Hystrix with Annotations
Java proxies automaticaly created
Annotations of javanica library
@EnableCircuitBreakeror @EnableHystrix, dependency to spring-cloud-starter-hystrix
@ H y s t r i x C o m m a n d ( f a l l b a c k M e t h o d = " g e t I t e m s C a c h e " , c o m m a n d P r o p e r t i e s = {
@ H y s t r i x P r o p e r t y ( n a m e = " c i r c u i t B r e a k e r . r e q u e s t V o l u m e T h r e s h o l d " , v a l u e = " 2 " )
} )
p u b l i c C o l l e c t i o n f i n d A l l ( ) {
t h i s . i t e m s C a c h e = . . .
. . .
r e t u r n p a g e d R e s o u r c e s . g e t C o n t e n t ( ) ;
}
p r i v a t e C o l l e c t i o n g e t I t e m s C a c h e ( ) {
r e t u r n i t e m s C a c h e ;
}

Turbine
Aggregates data from different Hystrix systems
The state of all Circuit Breakers can be summarized on a single dashboard

Turbine
@EnableTurbineand @EnableEurekaClient, dependency to spring-cloud-starter-turbine
Can use @EnableHystrixDashboardto display dahsboard on the same instance
Consolidated data determined by the con guration
t u r b i n e :
a g g r e g a t o r :
c l u s t e r C o n f i g : O R D E R
a p p C o n f i g : o r d e r

Conclusion
Easy to create new project
REST integrated
messaging supported
Simple deployment
Uniform operations

Thanks!
Any questions?
Microservices demo -
Travel demo -
https://github.com/ewolff/microservice
https://github.com/microservices-summit-2016/resilience-demo

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