How to set up a cache fallback in SpringBoot when unable to connect to Redis?

Question

There is a SpringBoot (v2.2.7) application, where a Redis cache is configured

fragment of pom.xml

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-cache</artifactId>
</dependency>

When the Redis service is up and available, caching works as expected: results of methods annotated with @Cacheable are being cached. Unfortunately, when Redis service is not available any call to a cacheable method leads to an exception RedisConnectionFailureException: Unable to connect to Redis.

I guess it is reasonable if the application could work (execute business logic) independently from the cache availability.

Possible solutions are:

1. custom implementation (i.e. a wrapper handling errors around the Redis cache)
2. standard configuration in Spring considering Redis cache service health (if there is such thing)

What is the proper way to set up a fallback cache in SpringBoot?

Answer 1

It can be done with the help of org.springframework.cache.interceptor.CacheErrorHandler

Out of the box you can use org.springframework.cache.interceptor.LoggingCacheErrorHandler implementation or make your own.

To register the CacheErrorHandler you configuration class must implement org.springframework.cache.annotation.CachingConfigurer interface.

See the following code excerpt as a reference

@Configuration
@EnableCaching
public class CacheConfiguration implements CachingConfigurer {

  @Override
  public CacheErrorHandler errorHandler() {
    return new LoggingCacheErrorHandler();
  }

  /*
  Just for reference.
   */
  @Bean
  public CacheManager cacheManager(LettuceConnectionFactory redisConnectionFactory) {
    return RedisCacheManager.RedisCacheManagerBuilder.fromConnectionFactory(redisConnectionFactory)
            .build();
  }
}