Springboot fail to start if Redis is down

Question

Redis is optional in my application & this is one of the requirement that even if Redis is down, application MUST be able to start without any issue.
I was able to handle this with spring-data-redis 1.8.1 version but it's causing issue when I upgraded to 2.0.1.
I was able to catch exception thrown during LettuceConnectionFactory but now it's throwing exception & control is not returned to calling class.
Please let me know how can I make Redis bean instantiation optional so that application server starts without any issue even if Redis is down.

SpringRedisConfig.java

   @Configuration
    public class SpringRedisConfig{
        private static final Logger logger = LoggerFactory.getLogger(SpringRedisConfig.class);

        @Value("${redis.config.file.path}")
        private String redisConfigFilePath;

        @Value("${redis.timeout}")
        private long redisTimeOut;

        public @Bean RedisTemplate redisTemplate(){
            RedisTemplate<String, Object> redisTemplate = null;
            try {
                redisTemplate = new RedisTemplate<>();
                redisTemplate.setKeySerializer(new StringRedisSerializer());
                redisTemplate.setHashKeySerializer(new StringRedisSerializer());
                redisTemplate.setHashValueSerializer(new GenericToStringSerializer<>(Long.class));
                redisTemplate.setConnectionFactory(connectionFactory());
            }catch(Exception e){
                logger.error("Error getting Redis Template connection ",e);
            }
            return redisTemplate;
        }

        @Bean
        public LettuceConnectionFactory connectionFactory() {
            LettuceConnectionFactory connectionFactory = null;
            try {
                ClientOptions clientOptions = ClientOptions.builder()
                        .cancelCommandsOnReconnectFailure(true)
                        .disconnectedBehavior(ClientOptions.DisconnectedBehavior.REJECT_COMMANDS)
                        .build();
                RedisStandaloneConfiguration standaloneConfig = new RedisStandaloneConfiguration("localhost",
                        6379);
                LettuceClientConfiguration lettuceClientConfiguration = LettuceClientConfiguration.builder().clientOptions(clientOptions).build();
                connectionFactory = new LettuceConnectionFactory(standaloneConfig, lettuceClientConfiguration);
            }catch(Exception e){
                logger.error("Error ",e);
            }
            return connectionFactory;
        }
    }

Console output:

main] o.s.boot.SpringApplication               : Application startup failed

    org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'redisCacheManagerController': Unsatisfied dependency expressed through field 'redisCacheManagerProvider'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'redisCacheManagerProvider': Unsatisfied dependency expressed through field 'redisTemplate'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'redisTemplate' defined in class path resource [com/kohls/jsl/cache/provider/config/SpringRedisConfig.class]: Invocation of init method failed; nested exception is java.lang.IllegalStateException: RedisConnectionFactory is required
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:588) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:366) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1264) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867) ~[spring-context-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543) ~[spring-context-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.5.8.RELEASE.jar:1.5.8.RELEASE]
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) [spring-boot-1.5.8.RELEASE.jar:1.5.8.RELEASE]
        at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) [spring-boot-1.5.8.RELEASE.jar:1.5.8.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) [spring-boot-1.5.8.RELEASE.jar:1.5.8.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) [spring-boot-1.5.8.RELEASE.jar:1.5.8.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) [spring-boot-1.5.8.RELEASE.jar:1.5.8.RELEASE]
        at com.kohls.browse.Application.main(Application.java:35) [classes/:na]
    Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'redisCacheManagerProvider': Unsatisfied dependency expressed through field 'redisTemplate'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'redisTemplate' defined in class path resource [com/kohls/jsl/cache/provider/config/SpringRedisConfig.class]: Invocation of init method failed; nested exception is java.lang.IllegalStateException: RedisConnectionFactory is required
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:588) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:366) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1264) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:208) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1138) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1066) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:585) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        ... 19 common frames omitted
    Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'redisTemplate' defined in class path resource [com/kohls/jsl/cache/provider/config/SpringRedisConfig.class]: Invocation of init method failed; nested exception is java.lang.IllegalStateException: RedisConnectionFactory is required
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1628) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:208) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1138) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1066) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:585) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        ... 32 common frames omitted
    Caused by: java.lang.IllegalStateException: RedisConnectionFactory is required
        at org.springframework.util.Assert.state(Assert.java:70) ~[spring-core-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.data.redis.core.RedisAccessor.afterPropertiesSet(RedisAccessor.java:38) ~[spring-data-redis-2.0.1.RELEASE.jar:2.0.1.RELEASE]
        at org.springframework.data.redis.core.RedisTemplate.afterPropertiesSet(RedisTemplate.java:123) ~[spring-data-redis-2.0.1.RELEASE.jar:2.0.1.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1687) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1624) ~[spring-beans-4.3.12.RELEASE.jar:4.3.12.RELEASE]
        ... 42 common frames omitted

Answer 1

Quick Solution: During spring initialization just catch the ERROR and return null. If Redis is down for any reason then it will return null. Catching an Error is not recommended but you can catch it technically. You have to make sure all the dependent services are null safe if you plan to return null as a fall back option. You can consider returning a mocked object as well.

@Bean 
public RedisTemplate redisTemplate(){          
RedisTemplate<String, Object> redisTemplate = null;
try {
    redisTemplate = new RedisTemplate<>();
    redisTemplate.setKeySerializer(new StringRedisSerializer());
    redisTemplate.setHashKeySerializer(new StringRedisSerializer());
    redisTemplate.setHashValueSerializer(new GenericToStringSerializer<>(Long.class));
    redisTemplate.setConnectionFactory(connectionFactory());
}catch(**Error** e){
    logger.error("Error getting Redis Template connection ",e);
}
return redisTemplate;
}

Preferred solution: Use different spring boot configurations depending on application profiles. You can find more about spring boot profiles here. You can set up different bean configurations for the development profile and just mock the required service without actually connecting to the Redis instance. You can also write logic conditionally. If the Redis service is up then return the actual instance or return the mocked object.

Potentially you can return mocked objects without using profiles but it is not recommended. Profiles will provide segregation of logic so that you don't enable such logic accidentally in the production environment.

Below is the sample code just to give some ideas. ActualRedisService and MockedRedisService will implement common interface RedisService.

MockedRedisService service will be having simple methods with no implementation whereas ActualRedisService will be connecting to the actual Redis instance.

@Bean 
@Profile("dev")
public RedisService redisService(){
  if(isEveryThingOkWithRedis()){
    return new ActualRedisService();
  }
  return new MockedRedisService();
}
   

I hope it is helpful.