This document discusses implementing cloud-native architectural patterns with Micronaut, including externalized configuration, service discovery, resiliency features like retries and circuit breakers, API versioning, and more. It provides code examples of configuring services for Consul-based service discovery and external configuration. It also shows how to add features like retries, timeouts, and fallbacks to make services more fault tolerant. The conclusion is that Micronaut makes it easier to implement cloud-native patterns and principles with built-in support for many of these features.

1. Implementing Cloud-Native
Architectural Patterns with
Micronaut
Naresha K
@naresha_k
https://blog.nareshak.com/

2. About me
Developer, Coach, Consultant
Founder & Organiser
Bangalore Groovy User Group

3. https://github.com/cncf/toc/blob/master/DEFINITION.md

4. https://www.redhat.com/en/topics/cloud-native-apps#

5. https://www.redhat.com/en/topics/cloud-native-apps#

6. Externalised Configuration

7. Configuration coupled with code
https://blog.nareshak.com/if-you-are-building-your-artifacts-per-environment-you-are-doing-it-wrong/

8. “Configuration should be
version controlled”

9. Configuration coupled with code

10. Externalising the configuration

11. @Controller("/hello")
public class HelloController {
@Value("${greeting.message}")
private String message;
@Get("/")
@Produces(MediaType.TEXT_PLAIN)
public String index() {
return message;
}
}

12. micronaut:
application:
name: hello-service
greeting:
message: Hello from Micronaut

13. java -Dmicronaut.environments=uat -jar
hello-service-0.1.jar

14. Configuration Injection

15. java -Dgreeting.message="Hello from External Config”
-jar hello-service-0.1.jar
java -Dmicronaut.config.files=“/tmp/external-config.yml"
-jar hello-service-0.1.jar

16. Is this not enough?

17. Config Server

18. Config
Server
Application
Application
Application

19. docker run -p 8500:8500 consul

22. bootstrap.yml

23. curl -X PUT -d @- localhost:8500/v1/kv/config/greet-service/greeting.message <<< "Hello from Consul"

24. ~ curl http://localhost:8080/greet
Hello from Consul

25. Service Discovery

26. Cloud Infrastructure

27. Microservices

28. Service
Registry
Service
X
Service A

29. Service
Registry
Service
X
Service A
Register

30. Service
Registry
Service
X
Service A
Register

31. Service
Registry
Service
X
Service A
Get routing information

32. Service
Registry
Service
X
Service A
REST call

35. ---
consul:
client:
registration:
enabled: true
defaultZone: "${CONSUL_HOST:localhost}:${CONSUL_PORT:8500}"
application.yml

36. sample-service ./gradlew run
> Task :run
05:12:07.121 [main] INFO io.micronaut.runtime.Micronaut - Startup completed in 1260ms. Server Running: http://localhost:8080
05:12:07.251 [nioEventLoopGroup-1-3] INFO i.m.d.registration.AutoRegistration - Registered service [sample-service] with Consul

37. http://localhost:8080/greet

38. @Controller("/hello")
class HelloController {
@Inject
GreetClient greetClient
@Get("/")
String index() {
greetClient.index()
}
}

40. Resiliency /
Fault Tolerance

41. https://en.wikipedia.org/wiki/Fallacies_of_distributed_computing

42. 07:19:19.838 [pool-1-thread-2] ERROR i.m.r.intercept.RecoveryInterceptor - Type
[com.nareshak.demo.GreetClient$Intercepted] attempting to resolve fallback for unavailable service
[sample-service]
07:19:19.843 [pool-1-thread-2] ERROR i.m.h.s.netty.RoutingInBoundHandler - Unexpected error occurred:
No available services for ID: sample-service
io.micronaut.discovery.exceptions.NoAvailableServiceException: No available services for ID: sample-
service at
io.micronaut.http.client.loadbalance.AbstractRoundRobinLoadBalancer.getNextAvailable(AbstractRoundRo
binLoadBalancer.java:50)

43. Timeout

44. 07:33:47.976 [pool-1-thread-3] ERROR i.m.r.intercept.RecoveryInterceptor - Type [com.nareshak.demo.GreetClient$Intercepted]
executed with error: Read Timeout
io.micronaut.http.client.exceptions.ReadTimeoutException: Read Timeout

45. Retry

46. @Retryable
String callExtService(){
}
@Retryable(attempts = "3", delay = "5s")
String callExtService(){
}

47. 07:26:27.347 [pool-1-thread-2] ERROR i.m.r.intercept.RecoveryInterceptor - Type [com.nareshak.demo.GreetClient$Intercepted]
attempting to resolve fallback for unavailable service [sample-service]
07:26:37.355 [pool-1-thread-2] ERROR i.m.r.intercept.RecoveryInterceptor - Type [com.nareshak.demo.GreetClient$Intercepted]
attempting to resolve fallback for unavailable service [sample-service]
07:26:52.361 [pool-1-thread-2] ERROR i.m.r.intercept.RecoveryInterceptor - Type [com.nareshak.demo.GreetClient$Intercepted]
attempting to resolve fallback for unavailable service [sample-service]
07:27:12.373 [pool-1-thread-2] ERROR i.m.r.intercept.RecoveryInterceptor - Type [com.nareshak.demo.GreetClient$Intercepted]
attempting to resolve fallback for unavailable service [sample-service]
07:27:12.378 [pool-1-thread-2] ERROR i.m.h.s.netty.RoutingInBoundHandler - Unexpected error occurred: No available services for
ID: sample-service
io.micronaut.discovery.exceptions.NoAvailableServiceException: No available services for ID: sample-service
at
io.micronaut.http.client.loadbalance.AbstractRoundRobinLoadBalancer.getNextAvailable(AbstractRoundRobinLoadBalancer.java:50)

48. Circuit Breakers

49. @CircuitBreaker
String callExtService(){
}
@CircuitBreaker(reset = "40s")
String callExtService(){
}

50. Fallback

51. @Fallback
class FallbackClient implements GreetClient{
@Override
String index() {
return "Default Message"
}
}

52. API Versioning

53. @Get(“/greet")
String index() {
"Hello"
}
@Get(“/greet")
Single<String> indexV2() {
Single.just("Hello V2")
}

54. @Get(“/greet")
@Version("1")
String index() {
"Hello"
}
@Get(“/greet")
@Version("2")
Single<String> indexV2() {
Single.just("Hello V2")
}

55. router:
versioning:
enabled: true
header:
enabled: true
names:
- 'X-API-VERSION'
- 'Accept-Version'
application.yml

56. ~curl http://localhost:8080/greet -H "X-API-VERSION: 1"
Hello%
~ curl http://localhost:8080/greet -H "X-API-VERSION: 2"
Hello V2%

57. @Client("sample-service")
@Version("1")
interface GreetClient {
@Get("/greet")
String index()
@Version("2")
@Get("/greet")
Single<String> indexV2()
}

58. When you in are in cloud-native world, features like fault tolerance,
service discovery, externalised configuration are necessary
Micronaut makes it easier to implement these patterns with its built-in support
Conclusion

59. Thank You