There are two microservices deployed with docker compose. A dependecy between services is defined in docker compose file by depends_on property. Is it possible to achieve the same effect implicitly, inside the spring boot application?
Let's say the microservice 1 depends on microservice 2. Which means, microsearvice 1 doesn't boot up before microservice 2 is healthy or registered on Eureka server.
By doing some research, I found a solution to the problem.
Spring Retry resolves dependency on Spring Cloud Config Server. Maven dependency spring-retry should be added into the pom.xml, and the properties below into the .properties file:
spring.cloud.config.fail-fast=true
spring.cloud.config.retry.max-interval=2000
spring.cloud.config.retry.max-attempts=10
The following configuration class is used to resolve dependency on other microservices.
@Configuration
@ConfigurationProperties(prefix = "depends-on")
@Data
@Log
public class DependsOnConfig {
private List<String> services;
private Integer periodMs = 2000;
private Integer maxAttempts = 20;
@Autowired
private EurekaClient eurekaClient;
@Bean
public void dependentServicesRegisteredToEureka() throws Exception {
if (services == null || services.isEmpty()) {
log.info("No dependent services defined.");
return;
}
log.info("Checking if dependent services are registered to eureka.");
int attempts = 0;
while (!services.isEmpty()) {
services.removeIf(this::checkIfServiceIsRegistered);
TimeUnit.MILLISECONDS.sleep(periodMs);
if (maxAttempts.intValue() == ++attempts)
throw new Exception("Max attempts exceeded.");
}
}
private boolean checkIfServiceIsRegistered(String service) {
try {
eurekaClient.getNextServerFromEureka(service, false);
log.info(service + " - registered.");
return true;
} catch (Exception e) {
log.info(service + " - not registered yet.");
return false;
}
}
}
A list of services that the current microservice depends on are defined in .properties file:
depends-on.services[0]=service-id-1
depends-on.services[1]=service-id-2
A bean dependentServicesRegisteredToEureka is not being initialized until all services from the list register to Eureka. If needed, annotation @DependsOn("dependentServicesRegisteredToEureka") can be added to beans or components to prevent attempting an initialization before dependentServicesRegisteredToEureka initialize.
eureka.client.registry-fetch-interval-seconds property to 10s because the default value is the 90s and it's too long to wait for registry refresh.