[FIXED] Reactive Redis:Spring Boot Application Start Fails, If Redis is Unavailable

Issue

We are using Reactive Redis to cache web-client response.If Redis server is up and running application works fine.But App start up is failing ,if we stop redis. Expected behavior is app should still go ahead and start even though redis connection fails.Does spring handles connection exception?or do we have to handle this kind of exceptions?

Here is the code I used to configure redis;

import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.ReactiveRedisConnection;
import org.springframework.data.redis.connection.ReactiveRedisConnectionFactory;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory;
import org.springframework.data.redis.core.ReactiveRedisTemplate;
import org.springframework.data.redis.serializer.RedisSerializationContext;

@Configuration
@ConditionalOnClass({ReactiveRedisTemplate.class, RedisConnectionFactory.class,
                     LettuceConnectionFactory.class, ReactiveRedisConnectionFactory.class})
public class RedisConfiguration {

    @Bean
    public ReactiveRedisConnectionFactory reactiveRedisConnectionFactory() {
        return new LettuceConnectionFactory();
    }

    @Bean
    public ReactiveRedisConnection reactiveRedisConnection(final ReactiveRedisConnectionFactory redisConnectionFactory) {
        return redisConnectionFactory.getReactiveConnection();
    }
    @Bean
    public ReactiveRedisTemplate<String, String> reactiveRedisTemplateString
            (ReactiveRedisConnectionFactory connectionFactory) {
        return new ReactiveRedisTemplate<>(connectionFactory, RedisSerializationContext.string());
    }
}

Exception

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'reactiveRedisConnection' defined in class path resource 
org.springframework.data.redis.RedisConnectionFailureException: Unable to connect to Redis; nested exception is io.lettuce.core.RedisConnectionException: Unable to connect to localhost:6379
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:655)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:635)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1338)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:893)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:879)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:551)
    at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.refresh(ReactiveWebServerApplicationContext.java:62)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:758)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:750)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226)
    at com.demo.obapi.redis.Application.main(Application.:30)
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.redis.connection.ReactiveRedisConnection]: Factory method 'reactiveRedisConnection' threw exception; nested exception is org.springframework.data.redis.RedisConnectionFailureException: Unable to connect to Redis; nested exception is io.lettuce.core.RedisConnectionException: Unable to connect to localhost:6379
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:650)
    ... 20 common frames omitted
Caused by: org.springframework.data.redis.RedisConnectionFailureException: Unable to connect to Redis; nested exception is io.lettuce.core.RedisConnectionException: Unable to connect to localhost:6379
    at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory$SharedConnection.getNativeConnection(LettuceConnectionFactory.java:1227)
    at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory$SharedConnection.getConnection(LettuceConnectionFactory.java:1206)
    at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory.getSharedReactiveConnection(LettuceConnectionFactory.java:980)
    at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory.getReactiveConnection(LettuceConnectionFactory.java:441)
    at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory.getReactiveConnection(LettuceConnectionFactory.java:95)
    at com.demo.example.redis.cache.config.RedisConfiguration.reactiveRedisConnection(RedisConfiguration.java:63)
    at com.demo.example.redis.cache.config.RedisConfiguration$$EnhancerBySpringCGLIB$$63b514a4.CGLIB$reactiveRedisConnection$0(<generated>)
    at com.demo.example.redis.cache.config.RedisConfiguration$$EnhancerBySpringCGLIB$$63b514a4$$FastClassBySpringCGLIB$$a05cf79e.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244)
    at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:331)
    at com.demo.obapi.redis.cache.config.RedisConfiguration$$EnhancerBySpringCGLIB$$63b514a4.reactiveRedisConnection(<generated>)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
    ... 21 common frames omitted
Caused by: io.lettuce.core.RedisConnectionException: Unable to connect to localhost:6379
    at io.lettuce.core.RedisConnectionException.create(RedisConnectionException.java:78)
    at io.lettuce.core.RedisConnectionException.create(RedisConnectionException.java:56)
    at io.lettuce.core.AbstractRedisClient.getConnection(AbstractRedisClient.java:234)
    at io.lettuce.core.RedisClient.connect(RedisClient.java:207)
    at org.springframework.data.redis.connection.lettuce.StandaloneConnectionProvider.lambda$getConnection$1(StandaloneConnectionProvider.java:115)
    at java.base/java.util.Optional.orElseGet(Optional.java:369)
    at org.springframework.data.redis.connection.lettuce.StandaloneConnectionProvider.getConnection(StandaloneConnectionProvider.java:115)
    at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory$SharedConnection.getNativeConnection(LettuceConnectionFactory.java:1225)
    ... 36 common frames omitted
Caused by: io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: localhost/127.0.0.1:6379
Caused by: java.net.ConnectException: Connection refused
    at java.base/sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
    at java.base/sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:779)
    at io.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:330)
    at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:334)
    at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:702)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:650)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:576)
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493)
    at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
    at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    at java.base/java.lang.Thread.run(Thread.java:834)

Solution

Spring boot automatically handles redis connection, we don't need our own custom class.Removed above class from my code, now I can see connection fails but app starts successfully.

Answered By - Rocky4Ever
Answer Checked By - Gilberto Lyons (JavaFixing Admin)