I have a simple microservices based app. It has 3 microservices. Movie-Catalog-Service, Ratings-Data-Service, Movie-Info-Service. Movie-Catalog-Service is dependent on Ratings-Data-Service and Movie-Info-Service. I have a getUserRating() inside the UserRatingInfo servcie class which is protected by a CircuitBreaker. When I deliberately have not started the Ratings-Data-Service and hit /catalog/10 I see:

java.lang.IllegalStateException: No instances available for ratings-data-service instead of the fallback method being executed.

package com.example.discoveryserver2;

import .springframework.boot.SpringApplication;
import .springframework.boot.autoconfigure.SpringBootApplication;
import .springframework.cloudflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
@EnableEurekaServer
public class DiscoveryServer2Application {

    public static void main(String[] args) {
        SpringApplication.run(DiscoveryServer2Application.class, args);
    }

}

package com.example.moviecatalogservice2;

import .springframework.boot.SpringApplication;
import .springframework.boot.autoconfigure.SpringBootApplication;
import .springframework.cloud.client.loadbalancer.LoadBalanced;
import .springframework.context.annotation.Bean;
import .springframework.web.client.RestTemplate;

@SpringBootApplication
public class MovieCatalogService2Application {

    public static void main(String[] args) {
        SpringApplication.run(MovieCatalogService2Application.class, args);
    }
    
    @Bean
    @LoadBalanced
    public RestTemplate getRestTemplate() {
        return new RestTemplate();
    }

}

package com.example.movieinfoservice2;

import .springframework.boot.SpringApplication;
import .springframework.boot.autoconfigure.SpringBootApplication;
import .springframework.context.annotation.Bean;
import .springframework.http.client.HttpComponentsClientHttpRequestFactory;
import .springframework.web.client.RestTemplate;

@SpringBootApplication
public class MovieInfoService2Application {

    public static void main(String[] args) {
        SpringApplication.run(MovieInfoService2Application.class, args);
    }
    
    @Bean
    public RestTemplate getRestTemplate() {
        HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory();
        clientHttpRequestFactory.setConnectTimeout(3000);
        return new RestTemplate();
    }

}

package com.example.ratingsdataservice2;

import .springframework.boot.SpringApplication;
import .springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class RatingsDataService2Application {

    public static void main(String[] args) {
        SpringApplication.run(RatingsDataService2Application.class, args);
    }

}

package com.example.moviecatalogservice2.resources;

import java.util.List;
import java.util.stream.Collectors;

import .springframework.beans.factory.annotation.Autowired;
import .springframework.web.bind.annotation.PathVariable;
import .springframework.web.bind.annotation.RequestMapping;
import .springframework.web.bind.annotation.RestController;

import com.example.moviecatalogservice2.models.CatalogItem;
import com.example.moviecatalogservice2.models.UserRating;
import com.example.moviecatalogservice2.services.MovieInfo;
import com.example.moviecatalogservice2.services.UserRatingInfo;

@RestController
@RequestMapping("/catalog")
public class CatalogResource {
    
    @Autowired
    private MovieInfo movieInfo;
    
    @Autowired
    private UserRatingInfo userRatingInfo;

    @RequestMapping("/{userId}")
    public List<CatalogItem> getCatalog(@PathVariable("userId") String userId) {

        UserRating userRating = userRatingInfo.getUserRating(userId);

        return userRating.getRatings().stream()
                .map(rating -> {
                    return movieInfo.getCatalogItem(rating);
                })
                .collect(Collectors.toList());
    }
    
}

package com.example.moviecatalogservice2.services;

import java.util.Arrays;

import .springframework.beans.factory.annotation.Autowired;
import .springframework.stereotype.Service;
import .springframework.web.client.RestTemplate;

import com.example.moviecatalogservice2.models.Rating;
import com.example.moviecatalogservice2.models.UserRating;

import io.github.resilience4j.circuitbreaker.annotation.CircuitBreaker;


@Service
public class UserRatingInfo {
    
    @Autowired
    private RestTemplate restTemplate;

    @CircuitBreaker(name = "ratings-data-service-cb", fallbackMethod = "getFallbackUserRating")
    public UserRating getUserRating(String userId) {
        UserRating userRating = restTemplate.getForObject("http://ratings-data-service/ratingsdata/user/{userId}", UserRating.class, userId);
        return userRating;
    }
    
    public UserRating getFallbackUserRating(String userId, Exception exc) {
        UserRating userRating =  new UserRating();
        userRating.setUserId(userId);
        userRating.setRatings(Arrays.asList(new Rating("100", 0)));
        return userRating;
    }
    
}

pom.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns=".0.0" xmlns:xsi=";
    xsi:schemaLocation=".0.0 .0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.4.4</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>movie-catalog-service-2</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>
    <name>movie-catalog-service-2</name>
    <description>Demo spring project for practicing Resilience4j</description>
    <url/>
    <licenses>
        <license/>
    </licenses>
    <developers>
        <developer/>
    </developers>
    <scm>
        <connection/>
        <developerConnection/>
        <tag/>
        <url/>
    </scm>
    <properties>
        <java.version>21</java.version>
        <spring-cloud.version>2024.0.1</spring-cloud.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-circuitbreaker-resilience4j</artifactId>
        </dependency>
        <dependency>
            <groupId>.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>

        <dependency>
            <groupId>.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <annotationProcessorPaths>
                        <path>
                            <groupId>.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </path>
                    </annotationProcessorPaths>
                </configuration>
            </plugin>
            <plugin>
                <groupId>.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

application.properties:

spring.application.name=movie-catalog-service

server.port = 8081

# This property allows us to specify the hostname that the service registers with Eureka.
eureka.instance.hostname = localhost

# Circuit Breaker for movie-info-service-cb
resilience4j.circuitbreaker.instances.movie-info-service-cb.sliding-window-type=count_based
resilience4j.circuitbreaker.instances.movie-info-service-cb.sliding-window-size=15
resilience4j.circuitbreaker.instances.movie-info-service-cb.minimum-number-of-calls=10
resilience4j.circuitbreaker.instances.movie-info-service-cb.failure-rate-threshold=50
resilience4j.circuitbreaker.instances.movie-info-service-cb.slow-call-rate-threshold=90
resilience4j.circuitbreaker.instances.movie-info-service-cb.slow-call-duration-threshold=4000
resilience4j.circuitbreaker.instances.movie-info-service-cb.wait-duration-in-open-state=20000
resilience4j.circuitbreaker.instances.movie-info-service-cb.max-wait-duration-in-half-open-state=6000
resilience4j.circuitbreaker.instances.movie-info-service-cb.permitted-number-of-calls-in-half-open-state=3

# Circuit Breaker for ratings-data-service-cb
resilience4j.circuitbreaker.instances.ratings-data-service-cb.sliding-window-type=time_based
resilience4j.circuitbreaker.instances.ratings-data-service-cb.sliding-window-size=60
resilience4j.circuitbreaker.instances.ratings-data-service-cb.minimum-number-of-calls=10
resilience4j.circuitbreaker.instances.ratings-data-service-cb.failure-rate-threshold=40
resilience4j.circuitbreaker.instances.ratings-data-service-cb.slow-call-rate-threshold=60
resilience4j.circuitbreaker.instances.ratings-data-service-cb.slow-call-duration-threshold=2000
resilience4j.circuitbreaker.instances.ratings-data-service-cb.wait-duration-in-open-state=10000
resilience4j.circuitbreaker.instances.ratings-data-service-cb.max-wait-duration-in-half-open-state=6000
resilience4j.circuitbreaker.instances.ratings-data-service-cb.permitted-number-of-calls-in-half-open-state=3