Groovy / Maven

Consul and the Micronaut Framework - Microservices Service Discovery

Use Consul service discovery to expose your Micronaut applications.

Sergio del Amo

On this guide

In this section

Getting Started

In this guide, we will create three microservices and register them with Consul Service discovery.

Consul is a distributed service mesh to connect, secure, and configure services across any runtime platform and public or private cloud.

You will discover how the Micronaut framework eases Consul integration.

What you will need

To complete this guide, you will need the following:

Some time on your hands
A decent text editor or IDE (e.g. IntelliJ IDEA)
JDK 21 or greater installed with JAVA_HOME configured appropriately

Solution

We recommend that you follow the instructions in the next sections and create the application step by step. However, you can go right to the completed example.

Download and unzip the source

Writing the App

Let’s describe the microservices you will build through the guide.

bookcatalogue - It returns a list of books. It uses a domain consisting of a book name and an ISBN.
bookinventory - It exposes an endpoint to check whether a book has sufficient stock to fulfill an order. It uses a domain consisting of a stock level and an ISBN.
bookrecommendation - It consumes previous services and exposes an endpoint that recommends book names that are in stock.

Initially, we will hard-code the service addresses in the bookcatalogue service.

As shown in the previous image, the bookcatalogue hardcodes references to its collaborators.

In the second part of this guide, we will use a discovery service.

Note	About registration patterns We will use a self‑registration pattern. Thus, each service instance is responsible for registering and deregistering itself with the service registry. Also, if required, a service instance sends heartbeat requests to prevent its registration from expiring.

Services register when they start up:

We will use client‑side service discovery. Clients query the service registry, select an available instance, and make a request.

Setup IntelliJ IDEA to develop Micronaut Applications.

Catalogue Microservice

Create the bookcatalogue microservice using the Micronaut Command Line Interface or with Micronaut Launch.

mn create-app --features=discovery-consul,management,graalvm example.micronaut.bookcatalogue --build=maven --lang=groovy

Note	If you don’t specify the `--build` argument, Gradle with the Kotlin DSL is used as the build tool. If you don’t specify the `--lang` argument, Java is used as the language. If you don’t specify the `--test` argument, JUnit is used for Java and Kotlin, and Spock is used for Groovy.

If you use Micronaut Launch, select Micronaut Application as application type and add the discovery-consul, management, and graalvm features.

The previous command creates a directory named bookcatalogue and a Micronaut application inside it with default package example.micronaut.

Note	If you have an existing Micronaut application and want to add the functionality described here, you can view the dependency and configuration changes from the specified features, and apply those changes to your application.

Diff

Create a BooksController class to handle incoming HTTP requests into the bookcatalogue microservice:

bookcatalogue/groovy/src/main/groovy/example/micronaut/BooksController.groovy

package example.micronaut

import groovy.transform.CompileStatic
import io.micronaut.http.annotation.Controller
import io.micronaut.http.annotation.Get

@CompileStatic
@Controller("/books") // 
class BooksController {

    @Get // 
    List<Book> index() {
        [
            new Book("1491950358", "Building Microservices"),
            new Book("1680502395", "Release It!"),
            new Book("0321601912", "Continuous Delivery:")
        ]
    }
}

1	The class is defined as a controller with the @Controller annotation mapped to the path `/`.
2	The @Get annotation maps the `index` method to an HTTP GET request on `/books`.

The previous controller responds with a List<Book>. Create the Book POJO:

bookcatalogue/groovy/src/main/groovy/example/micronaut/Book.groovy

package example.micronaut

import groovy.transform.CompileStatic
import groovy.transform.EqualsAndHashCode
import io.micronaut.core.annotation.Creator
import io.micronaut.core.annotation.NonNull
import io.micronaut.serde.annotation.Serdeable

import jakarta.validation.constraints.NotBlank

@CompileStatic
@EqualsAndHashCode
@Serdeable
class Book {

    @NonNull
    @NotBlank
    final String isbn

    @NonNull
    @NotBlank
    final String name

    @Creator
    Book(@NonNull @NotBlank String isbn,
         @NonNull @NotBlank String name) {
        this.isbn = isbn
        this.name = name
    }
}

Write a test:

bookcatalogue/groovy/src/test/groovy/example/micronaut/BooksControllerSpec.groovy

package example.micronaut

import io.micronaut.core.type.Argument
import io.micronaut.http.HttpRequest
import io.micronaut.http.client.HttpClient
import io.micronaut.http.client.annotation.Client
import io.micronaut.test.extensions.spock.annotation.MicronautTest
import jakarta.inject.Inject
import spock.lang.Specification

@MicronautTest // 
class BooksControllerSpec extends Specification {

    @Inject
    @Client("/")
    HttpClient client // 

    void "it is possible to retrieve books"() {
        when:
        HttpRequest request = HttpRequest.GET("/books") // 
        List<Book> books = client.toBlocking().retrieve(request, Argument.listOf(Book)) // 

        then:
        books.size() == 3
        books.contains(new Book("1491950358", "Building Microservices"))
        books.contains(new Book("1680502395", "Release It!"))
    }
}

1	Annotate the class with `@MicronautTest` so the Micronaut framework will initialize the application context and the embedded server. More info.
2	Inject the `HttpClient` bean and point it to the embedded server.
3	Creating HTTP Requests is easy thanks to the Micronaut framework fluid API.
4	Easily parse JSON into Java objects.

Edit application.properties

bookcatalogue/src/main/resources/application.properties

micronaut.application.name=bookcatalogue

1	Configure the application name. The application name will be used by the discovery service.

Modify the Application class to use dev as a default environment:

The Micronaut framework supports the concept of one or many default environments. A default environment is one that is only applied if no other environments are explicitly specified or deduced.

bookcatalogue/groovy/src/main/groovy/example/micronaut/Application.groovy

package example.micronaut

import groovy.transform.CompileStatic
import io.micronaut.runtime.Micronaut

import static io.micronaut.context.env.Environment.DEVELOPMENT

@CompileStatic
class Application {

    static void main(String[] args) {
        Micronaut.build(args)
                .mainClass(Application)
                .defaultEnvironments(DEVELOPMENT)
                .start()
    }
}

Create src/main/resources/application-dev.properties. The Micronaut framework applies this configuration file only for the dev environment.

bookcatalogue/src/main/resources/application-dev.properties

micronaut.server.port=8081

1	Configure the application to listen on port 8081.

Create a file named application-test.properties which is used in the test environment:

bookcatalogue/src/test/resources/application-test.properties

consul.client.registration.enabled=false

Run the unit test:

bookcatalogue

./mvnw test

Inventory Microservice

Create the bookinventory microservice using the Micronaut Command Line Interface or with Micronaut Launch.

mn create-app --features=discovery-consul,management,graalvm example.micronaut.bookinventory --build=maven --lang=groovy

Note	If you don’t specify the `--build` argument, Gradle with the Kotlin DSL is used as the build tool. If you don’t specify the `--lang` argument, Java is used as the language. If you don’t specify the `--test` argument, JUnit is used for Java and Kotlin, and Spock is used for Groovy.

If you use Micronaut Launch, select Micronaut Application as application type and add the discovery-consul, management, and graalvm features.

The previous command creates a directory named bookinventory and a Micronaut application inside it with default package example.micronaut.

Note	If you have an existing Micronaut application and want to add the functionality described here, you can view the dependency and configuration changes from the specified features, and apply those changes to your application.

Diff

Create a Controller:

bookinventory/groovy/src/main/groovy/example/micronaut/BooksController.groovy

package example.micronaut

import groovy.transform.CompileStatic
import io.micronaut.http.annotation.Controller
import io.micronaut.http.annotation.Get
import io.micronaut.http.annotation.Produces

import jakarta.validation.constraints.NotBlank

import static io.micronaut.http.MediaType.TEXT_PLAIN

@CompileStatic
@Controller("/books") // 
class BooksController {

    @Produces(TEXT_PLAIN) // 
    @Get("/stock/{isbn}") // 
    Boolean stock(@NotBlank String isbn) {
        bookInventoryByIsbn(isbn).map(bi -> bi.stock > 0).orElse(null)
    }

    private Optional<BookInventory> bookInventoryByIsbn(String isbn) {
        if (isbn == "1491950358") {
            return Optional.of(new BookInventory(isbn, 4))
        }
        if (isbn == "1680502395") {
            return Optional.of(new BookInventory(isbn, 0))
        }
        Optional.empty()
    }
}

1	The class is defined as a controller with the @Controller annotation mapped to the path `/books`.
2	By default, `Content-Type` of a controller response is `application/json` : override this with `text/plain` since we are returning a String, not a JSON object.
3	The @Get annotation maps the `index` method to an HTTP GET request on `/books/stock/{isbn}`.

Create the POJO used by the controller:

bookinventory/groovy/src/main/groovy/example/micronaut/BookInventory.groovy

package example.micronaut

import groovy.transform.CompileStatic
import groovy.transform.EqualsAndHashCode
import io.micronaut.core.annotation.NonNull
import io.micronaut.serde.annotation.Serdeable

import jakarta.validation.constraints.NotBlank

@CompileStatic
@EqualsAndHashCode
@Serdeable
class BookInventory {

    @NonNull
    @NotBlank
    final String isbn

    final int stock

    BookInventory(@NonNull @NotBlank String isbn,
                  int stock) {
        this.isbn = isbn
        this.stock = stock
    }
}

Write a test:

bookinventory/groovy/src/test/groovy/example/micronaut/BooksControllerSpec.groovy

package example.micronaut

import io.micronaut.http.HttpRequest
import io.micronaut.http.HttpResponse
import io.micronaut.http.client.HttpClient
import io.micronaut.http.client.annotation.Client
import io.micronaut.http.client.exceptions.HttpClientResponseException
import io.micronaut.test.extensions.spock.annotation.MicronautTest
import jakarta.inject.Inject
import spock.lang.Specification

import static io.micronaut.http.HttpStatus.NOT_FOUND
import static io.micronaut.http.HttpStatus.OK

@MicronautTest
class BooksControllerSpec extends Specification {

    @Inject
    @Client("/")
    HttpClient httpClient

    void "for a book with inventory true is returned"() {
        when:
        HttpResponse<Boolean> rsp = httpClient.toBlocking().exchange(
                HttpRequest.GET("/books/stock/1491950358"), Boolean)

        then:
        rsp.status() == OK
        rsp.body()
    }

    void "for an invalid ISBN 404 is returned"() {
        when:
        httpClient.toBlocking().exchange(HttpRequest.GET("/books/stock/XXXXX"), Boolean)

        then:
        HttpClientResponseException e = thrown()
        e.response.status == NOT_FOUND
    }
}

Edit application.properties

bookinventory/src/main/resources/application.properties

micronaut.application.name=bookinventory

1	Configure the application name. The name will be used later in the guide.

Modify the Application class to use dev as a default environment:

The Micronaut framework supports the concept of one or many default environments. A default environment is one that is only applied if no other environments are explicitly specified or deduced.

bookinventory/groovy/src/main/groovy/example/micronaut/Application.groovy

package example.micronaut

import groovy.transform.CompileStatic
import io.micronaut.runtime.Micronaut

import static io.micronaut.context.env.Environment.DEVELOPMENT

@CompileStatic
class Application {

    static void main(String[] args) {
        Micronaut.build(args)
                .mainClass(Application)
                .defaultEnvironments(DEVELOPMENT)
                .start()
    }
}

Create src/main/resources/application-dev.properties. The Micronaut framework applies this configuration file only for the dev environment.

bookinventory/src/main/resources/application-dev.properties

micronaut.server.port=8082

1	Configure the application to listen on port 8082.

Create a file named application-test.properties which is used in the test environment:

bookinventory/src/test/resources/application-test.properties

consul.client.registration.enabled=false

Run the unit test:

bookinventory

./mvnw test

Recommendation Microservice

Create the bookrecommendation microservice using the Micronaut Command Line Interface or with Micronaut Launch.

mn create-app --features=discovery-consul,management,reactor,graalvm example.micronaut.bookrecommendation --build=maven --lang=groovy

Note	If you don’t specify the `--build` argument, Gradle with the Kotlin DSL is used as the build tool. If you don’t specify the `--lang` argument, Java is used as the language. If you don’t specify the `--test` argument, JUnit is used for Java and Kotlin, and Spock is used for Groovy.

If you use Micronaut Launch, select Micronaut Application as application type and add the discovery-consul, management, reactor, and graalvm features.

The previous command creates a directory named bookrecommendation and a Micronaut application inside it with default package example.micronaut.

Note	If you have an existing Micronaut application and want to add the functionality described here, you can view the dependency and configuration changes from the specified features, and apply those changes to your application.

Diff

Create an interface to map operations with bookcatalogue, and a Micronaut Declarative HTTP Client to consume it.

bookrecommendation/groovy/src/main/groovy/example/micronaut/BookCatalogueOperations.groovy

package example.micronaut

import org.reactivestreams.Publisher

interface BookCatalogueOperations {
    Publisher<Book> findAll()
}

bookrecommendation/groovy/src/main/groovy/example/micronaut/BookCatalogueClient.groovy

package example.micronaut

import io.micronaut.http.annotation.Get
import io.micronaut.http.client.annotation.Client
import io.micronaut.retry.annotation.Recoverable
import org.reactivestreams.Publisher

@Client("http://localhost:8081") // 
@Recoverable(api = BookCatalogueOperations)

interface BookCatalogueClient extends BookCatalogueOperations {

    @Get("/books")
    Publisher<Book> findAll()
}

1	Use `@Client` to use declarative HTTP Clients. You can annotate interfaces or abstract classes. You can use the `id` member to provide a service identifier or specify the URL directly as the annotation’s value.

The client returns a POJO. Create it in the bookrecommendation:

bookrecommendation/groovy/src/main/groovy/example/micronaut/Book.groovy

package example.micronaut

import groovy.transform.CompileStatic
import groovy.transform.EqualsAndHashCode
import io.micronaut.core.annotation.NonNull
import io.micronaut.serde.annotation.Serdeable

import jakarta.validation.constraints.NotBlank

@CompileStatic
@EqualsAndHashCode
@Serdeable
class Book {

    @NonNull
    @NotBlank
    final String isbn

    @NonNull
    @NotBlank
    final String name

    Book(@NonNull @NotBlank String isbn,
         @NonNull @NotBlank String name) {
        this.isbn = isbn
        this.name = name
    }
}

Create an interface to map operations with bookinventory, and a Micronaut Declarative HTTP Client to consume it.

bookrecommendation/groovy/src/main/groovy/example/micronaut/BookInventoryOperations.groovy

package example.micronaut

import io.micronaut.core.annotation.NonNull
import reactor.core.publisher.Mono

import jakarta.validation.constraints.NotBlank

interface BookInventoryOperations {
    Mono<Boolean> stock(@NonNull @NotBlank String isbn)
}

bookrecommendation/groovy/src/main/groovy/example/micronaut/BookInventoryClient.groovy

package example.micronaut

import io.micronaut.core.annotation.NonNull
import io.micronaut.http.annotation.Consumes
import io.micronaut.http.annotation.Get
import io.micronaut.http.client.annotation.Client
import io.micronaut.retry.annotation.Recoverable
import reactor.core.publisher.Mono

import jakarta.validation.constraints.NotBlank

import static io.micronaut.http.MediaType.TEXT_PLAIN

@Client("http://localhost:8082") // 
@Recoverable(api = BookInventoryOperations)

interface BookInventoryClient extends BookInventoryOperations {

    @Consumes(TEXT_PLAIN)
    @Get("/books/stock/{isbn}")
    Mono<Boolean> stock(@NonNull @NotBlank String isbn)
}

1	Use `@Client` to use declarative HTTP Clients. You can annotate interfaces or abstract classes. You can use the `id` member to provide a service identifier or specify the URL directly as the annotation’s value.

Create a Controller which injects both clients.

bookrecommendation/groovy/src/main/groovy/example/micronaut/BookController.groovy

package example.micronaut

import groovy.transform.CompileStatic
import io.micronaut.http.annotation.Controller
import io.micronaut.http.annotation.Get
import org.reactivestreams.Publisher
import reactor.core.publisher.Flux

@CompileStatic
@Controller("/books") // 
class BookController {

    private final BookCatalogueOperations bookCatalogueOperations
    private final BookInventoryOperations bookInventoryOperations

    BookController(BookCatalogueOperations bookCatalogueOperations,
                   BookInventoryOperations bookInventoryOperations) { // 
        this.bookCatalogueOperations = bookCatalogueOperations
        this.bookInventoryOperations = bookInventoryOperations
    }

    @Get // 
    Publisher<BookRecommendation> index() {
        Flux.from(bookCatalogueOperations.findAll())
                .flatMap(b -> Flux.from(bookInventoryOperations.stock(b.isbn))
                        .filter(Boolean::booleanValue)
                        .map(rsp -> b)
                ).map(book -> new BookRecommendation(book.name))
    }
}

1	The class is defined as a controller with the @Controller annotation mapped to the path `/books`.
2	Clients are injected via constructor injection
3	The @Get annotation maps the `index` method to an HTTP GET request on `/books`.

The previous controller returns a Publisher<BookRecommendation>. Create the BookRecommendation POJO:

bookrecommendation/groovy/src/main/groovy/example/micronaut/BookRecommendation.groovy

package example.micronaut

import groovy.transform.CompileStatic
import groovy.transform.EqualsAndHashCode
import io.micronaut.core.annotation.NonNull
import io.micronaut.serde.annotation.Serdeable

import jakarta.validation.constraints.NotBlank

@CompileStatic
@EqualsAndHashCode
@Serdeable
class BookRecommendation {

    @NonNull
    @NotBlank
    final String name

    BookRecommendation(@NonNull @NotBlank String name) {
        this.name = name
    }
}

BookCatalogueClient and BookInventoryClient will fail to consume the bookcatalogue and bookinventory during the tests phase.

Using the @Fallback annotation, you can declare a fallback implementation of a client that will be picked up and used once all possible retries have been exhausted.

Create @Fallback alternatives in the test classpath.

bookrecommendation/groovy/src/test/groovy/example/micronaut/BookInventoryClientStub.groovy

package example.micronaut

import io.micronaut.context.annotation.Requires
import io.micronaut.core.annotation.NonNull
import io.micronaut.retry.annotation.Fallback
import jakarta.inject.Singleton
import reactor.core.publisher.Mono

import jakarta.validation.constraints.NotBlank

import static io.micronaut.context.env.Environment.TEST

@Requires(env = TEST) // 
@Fallback
@Singleton
class BookInventoryClientStub implements BookInventoryOperations {

    @Override
    Mono<Boolean> stock(@NonNull @NotBlank String isbn) {
        if (isbn == "1491950358") {
            return Mono.just(true) // 
        }
        if (isbn == "1680502395") {
            return Mono.just(false) // 
        }
        Mono.empty() // 
    }
}

1	Make this fallback class effective only when the Micronaut environment TEST is active.
2	Here we arbitrarily decide that if everything else fails, that book’s `stock` would be true.
3	Similarly, we decide that the other book’s `stock` method would be false.
4	Finally, any other book will have its `stock` method return an empty value.

bookrecommendation/groovy/src/test/groovy/example/micronaut/BookCatalogueClientStub.groovy

package example.micronaut

import io.micronaut.context.annotation.Requires
import io.micronaut.retry.annotation.Fallback
import jakarta.inject.Singleton
import org.reactivestreams.Publisher
import reactor.core.publisher.Flux

import static io.micronaut.context.env.Environment.TEST

@Requires(env = TEST)
@Fallback
@Singleton
class BookCatalogueClientStub implements BookCatalogueOperations {

    @Override
    Publisher<Book> findAll() {
        Book buildingMicroservices = new Book("1491950358", "Building Microservices")
        Book releaseIt = new Book("1680502395", "Release It!")
        Flux.just(buildingMicroservices, releaseIt)
    }
}

Write a test:

bookrecommendation/groovy/src/test/groovy/example/micronaut/BookControllerSpec.groovy

package example.micronaut

import io.micronaut.http.HttpRequest
import io.micronaut.http.client.HttpClient
import io.micronaut.http.client.annotation.Client
import io.micronaut.test.extensions.spock.annotation.MicronautTest
import jakarta.inject.Inject
import io.micronaut.core.type.Argument
import spock.lang.IgnoreIf
import spock.lang.Specification

@MicronautTest
class BookControllerSpec extends Specification {

    @Inject
    @Client("/")
    HttpClient client

    @IgnoreIf({env['CI'] as boolean})
    void "retrieve books"() {
        when:
        List<BookRecommendation> books = client.toBlocking().retrieve(HttpRequest.GET("/books"), Argument.listOf(BookRecommendation))

        then:
        books.size() == 1
        books[0].name == "Building Microservices"
    }
}

Edit application.properties

bookrecommendation/src/main/resources/application.properties

micronaut.application.name=bookrecommendation

1	Configure the application name. The name will be used later in the guide.

Modify the Application class to use dev as a default environment:

The Micronaut framework supports the concept of one or many default environments. A default environment is one that is only applied if no other environments are explicitly specified or deduced.

bookrecommendation/groovy/src/main/groovy/example/micronaut/Application.groovy

package example.micronaut

import groovy.transform.CompileStatic
import io.micronaut.runtime.Micronaut

import static io.micronaut.context.env.Environment.DEVELOPMENT

@CompileStatic
class Application {

    static void main(String[] args) {
        Micronaut.build(args)
                .mainClass(Application)
                .defaultEnvironments(DEVELOPMENT)
                .start()
    }
}

Create src/main/resources/application-dev.properties. The Micronaut framework applies this configuration file only for the dev environment.

bookrecommendation/src/main/resources/application-dev.properties

micronaut.server.port=8080

1	Configure the application to listen on port 8080

Create a file named application-test.properties which is used in the test environment:

bookrecommendation/src/test/resources/application-test.properties

consul.client.registration.enabled=false

Run the unit test:

bookrecommendation

./mvnw test

Running the application

Run bookcatalogue microservice:

bookcatalogue

./mvnw mn:run

14:28:34.034 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 499ms. Server Running: http://localhost:8081

Run bookinventory microservice:

bookinventory

./mvnw mn:run

14:31:13.104 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 506ms. Server Running: http://localhost:8082

Run bookrecommendation microservice:

bookrecommendation

./mvnw mn:run

14:31:57.389 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 523ms. Server Running: http://localhost:8080

You can run a cURL command to test the whole application:

curl http://localhost:8080/books

[{"name":"Building Microservices"}]

Consul and the Micronaut framework

Install Consul via Docker

The quickest way to start using Consul is via Docker:

docker run -p 8500:8500 consul

Alternatively you can install and run a local Consul instance.

The following screenshots show how to install/run Consul via Kitematic, a UI for Docker.

Configure ports:

Book Catalogue

Append the following snippet to the bookcatalogue service application.properties:

bookcatalogue/src/main/resources/application.properties

consul.client.registration.enabled=true
consul.client.defaultZone=${CONSUL_HOST:localhost}:${CONSUL_PORT:8500}

This configuration registers a Micronaut application with Consul with minimal configuration. Discover a more complete list of configuration options at ConsulConfiguration.

Book Inventory

Modify the application.properties of the bookinventory application with the following snippet:

bookinventory/src/main/resources/application.properties

consul.client.registration.enabled=true
consul.client.defaultZone=${CONSUL_HOST:localhost}:${CONSUL_PORT:8500}

Book Recommendation

Append the following snippet to the bookrecommendation service application.properties:

bookrecommendation/src/main/resources/application.properties

consul.client.registration.enabled=true
consul.client.defaultZone=${CONSUL_HOST:localhost}:${CONSUL_PORT:8500}

Modify BookInventoryClient and BookCatalogueClient to use the service id instead of a hard-coded URL.

bookrecommendation/groovy/src/main/groovy/example/micronaut/BookCatalogueClient.groovy

package example.micronaut

import io.micronaut.http.annotation.Get
import io.micronaut.http.client.annotation.Client
import io.micronaut.retry.annotation.Recoverable
import org.reactivestreams.Publisher

@Client(id = "bookcatalogue") // 
@Recoverable(api = BookCatalogueOperations)

interface BookCatalogueClient extends BookCatalogueOperations {

    @Get("/books")
    Publisher<Book> findAll()
}

1	Use the configuration value `micronaut.application.name` used in `bookcatalogue` as service `id`.

bookrecommendation/groovy/src/main/groovy/example/micronaut/BookInventoryClient.groovy

package example.micronaut

import io.micronaut.core.annotation.NonNull
import io.micronaut.http.annotation.Consumes
import io.micronaut.http.annotation.Get
import io.micronaut.http.client.annotation.Client
import io.micronaut.retry.annotation.Recoverable
import reactor.core.publisher.Mono

import jakarta.validation.constraints.NotBlank

import static io.micronaut.http.MediaType.TEXT_PLAIN

@Client(id = "bookinventory") // 
@Recoverable(api = BookInventoryOperations)

interface BookInventoryClient extends BookInventoryOperations {

    @Consumes(TEXT_PLAIN)
    @Get("/books/stock/{isbn}")
    Mono<Boolean> stock(@NonNull @NotBlank String isbn)
}

1	Use the configuration value `micronaut.application.name` used in `bookinventory` as service `id`.

Running the App

Run bookcatalogue microservice:

bookcatalogue

./gradlew run

14:28:34.034 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 499ms. Server Running: http://localhost:8081
14:28:34.084 [nioEventLoopGroup-1-3] INFO  i.m.d.registration.AutoRegistration - Registered service [bookcatalogue] with Consul

Run bookinventory microservice:

bookinventory

./gradlew run

14:31:13.104 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 506ms. Server Running: http://localhost:8082
14:31:13.154 [nioEventLoopGroup-1-3] INFO  i.m.d.registration.AutoRegistration - Registered service [bookinventory] with Consul

Run bookrecommendation microservice:

bookrecommendation

./gradlew run

14:31:57.389 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 523ms. Server Running: http://localhost:8080
14:31:57.439 [nioEventLoopGroup-1-3] INFO  i.m.d.registration.AutoRegistration - Registered service [bookrecommendation] with Consul

Consul comes with a HTML UI. Open http://localhost:8500/ui in your browser.

You will see the services registered in Consul:

You can run a cURL command to test the whole application:

curl http://localhost:8080/books

[{"name":"Building Microservices"}]

Next Steps

Read more about Consul support in the Micronaut framework.

Help with the Micronaut Framework

The Micronaut Foundation sponsored the creation of this Guide. A variety of consulting and support services are available.

License

Note	All guides are released with an Apache License 2.0 for the code and a Creative Commons Attribution 4.0 license for the writing and media (images).