This document discusses leveraging Micronaut, an open source Java framework, to build serverless applications on AWS Lambda. It demonstrates how to create a Micronaut function that converts temperatures between Celsius and Fahrenheit and deploy it to AWS Lambda. It also shows how to test the function locally and with unit tests using the Micronaut test support. The function can then be invoked remotely and from other applications using a generated client. Micronaut provides features like dependency injection that reduce overhead compared to traditional Lambda applications.

2. Leveraging Micronaut on AWS Lambda
Naresha K
Continuous Delivery Architect | Technical Excellence Coach
naresha.k@gmail.com
@naresha_k

3. IaaS
PaaS
SaaS

4. IaaS
PaaS
SaaS
FaaS
CaaS

5. IaaS
PaaS
SaaS
FaaS
CaaS

7. ➜ ~ sdk install micronaut
https://sdkman.io/

8. ➜ ~ mn

9. ➜ ~ mn
| Starting interactive mode...
| Enter a command name to run. Use TAB for completion:
mn>

10. ➜ ~ mn
| Starting interactive mode...
| Enter a command name to run. Use TAB for completion:
mn> create-function temperature-converter

11. ➜ ~ mn
| Starting interactive mode...
| Enter a command name to run. Use TAB for completion:
mn>create-function temperature-converter
| Generating Java project...
| Function created at /Users/naresha/practice/micronaut/
awsdaysblr/temperature-converter
| Initializing application. Please wait...
mn>

13. @Getter
@Setter
@NoArgsConstructor
@Introspected
public class Temperature {
private double inCelcius;
private double inFahrenheit;
public static Temperature ofCelcius(double celcius) {
Temperature temperature = new Temperature();
temperature.setInCelcius(celcius);
return temperature;
}
public static Temperature ofFahrenheit(double fahrenheit) {
Temperature temperature = new Temperature();
temperature.setInFahrenheit(fahrenheit);
return temperature;
}
}

14. @FunctionBean("temperature-converter")
public class TemperatureConverterFunction
}

15. @FunctionBean("temperature-converter")
public class TemperatureConverterFunction
implements Function<Temperature, Temperature> {
}

16. @FunctionBean("temperature-converter")
public class TemperatureConverterFunction
implements Function<Temperature, Temperature> {
@Override
public Temperature apply(Temperature input) {
return Temperature.ofFahrenheit(input.getInCelcius() * 9 / 5 + 32);
}
}

17. Deploying to AWS Lambda

18. ➜ temperature-converter ./gradlew assemble

19. ➜ temperature-converter ./gradlew assemble
> Task :compileJava
Note: Creating bean classes for 1 type elements
BUILD SUCCESSFUL in 5s
10 actionable tasks: 8 executed, 2 up-to-date
➜ temperature-converter

20. ➜ temperature-converter ./gradlew assemble
> Task :compileJava
Note: Creating bean classes for 1 type elements
BUILD SUCCESSFUL in 5s
10 actionable tasks: 8 executed, 2 up-to-date
➜ temperature-converter echo '{"inCelcius": 37}' | java -jar ./build/libs/
temperature-converter-0.1-all.jar

21. ➜ temperature-converter ./gradlew assemble
> Task :compileJava
Note: Creating bean classes for 1 type elements
BUILD SUCCESSFUL in 5s
10 actionable tasks: 8 executed, 2 up-to-date
➜ temperature-converter echo '{"inCelcius": 37}' | java -jar ./build/libs/
temperature-converter-0.1-all.jar
{"inCelcius":0.0,"inFahrenheit":98.6}

25. ➜ temperature-converter ./gradlew deploy
> Task :deploy
Function not found: arn:aws:lambda:us-east-1:341512844459:function:temperature-
converter-mn-java-2 (Service: AWSLambda; Status Code: 404; Error Code:
ResourceNotFoundException; Request ID: 0c789b90-e936-4663-ad68-2037c1a3b6ef)
Creating function... temperature-converter-mn-java-2
BUILD SUCCESSFUL in 57s
4 actionable tasks: 1 executed, 3 up-to-date
➜ temperature-converter

26. @FunctionBean("temperature-converter")
public class TemperatureConverterFunction extends FunctionInitializer
implements Function<Temperature, Temperature> {
@Override
public Temperature apply(Temperature input) {
return Temperature.ofFahrenheit(input.getInCelcius() * 9 / 5 + 32);
}
public static void main(String... args) throws IOException {
TemperatureConverterFunction function =
new TemperatureConverterFunction();
function.run(args, (context) ->
function.apply(context.get(Temperature.class)));
}
}

27. package com.nareshak.demo
Temperature temperatureConverter(Temperature input) {
new Temperature(inFahrenheit:
input.getInCelcius() * 9 / 5 + 32)
}

28. package com.nareshak.demo
import groovy.transform.Field
import javax.inject.Inject
@Field @Inject TemperatureConveterService temperatureConveterService
Temperature temperatureConverter(Temperature input) {
new Temperature(inFahrenheit:
temperatureConveterService
.celciusToFahrenheit(input.inCelcius))
}

29. package com.nareshak.demo
import javax.inject.Singleton
@Singleton
class TemperatureConveterService {
double celciusToFahrenheit(double celcius) {
celcius * 9 / 5 + 32
}
}

30. Testing Functions

31. package temperature.converter;
import io.micronaut.test.annotation.MicronautTest;
import org.junit.jupiter.api.Test;
import javax.inject.Inject;
import static org.junit.jupiter.api.Assertions.assertEquals;
@MicronautTest
public class TemperatureConverterFunctionTest {
@Inject
TemperatureConverterClient client;
@Test
public void testFunction() throws Exception {
Temperature body = Temperature.ofCelcius(37.0);
assertEquals(98.6, client.apply(body).blockingGet().getInFahrenheit());
}
}

32. package com.nareshak.demo
import io.micronaut.test.annotation.MicronautTest
import spock.lang.Specification
import javax.inject.Inject
@MicronautTest
class TemperatureConverterFunctionSpec extends Specification {
@Inject
TemperatureConverterClient client
void "test temperature-converter-groovy function"() {
given:
Temperature temperature = new Temperature(inCelcius: 37)
expect:
client.convertTemperature(temperature).blockingGet().inFahrenheit == 98.6
}
}

33. Function Client

34. @FunctionClient
interface TemperatureConverterClient {
@Named("temperature-converter")
Single<Temperature> convertTemperature(Temperature input)
}

35. micronaut:
application:
name: clientapp
---
aws:
lambda:
functions:
convertTemperature:
functionName: temperature-converter
region: us-east-1

36. @Controller
class MainController {
@Inject
TemperatureConverter temperatureConverter
@Get("/")
String index() {
def temperature = new Temperature(inCelcius: 37)
Temperature result = temperatureConverter
.convertTemperature(temperature)
.blockingGet()
result.toString()
}
}

37. Compile-time dependency injection
=>
less runtime overhead

38. https://github.com/naresha/awscommunitydayblr_micronaut_faas

39. Thank You