Clear Redis Cache on Spring Boot Application Startup

Question

On application (spring boot service) startup, need to clear the Redis cache.

Redis is running in a different docker container with own volume mapping. Since it retains the old cache, the application picks the data from Redis cache instead of Database even after the application restarts

• Tried @EventListener for ContextRefreshedEvent and it is never getting called.
• Tried with @PostConstruct in ApplicationMain class, but it doesn't clear the cache.

• Tried using @CacheEvict(allEntries = true), but still no luck

  @Component public class ApplicationStartUp {

  @Autowired
  private CacheManager cacheManager;
  
  @EventListener()
  public void onApplicationEvent(ContextStartedEvent event) {
      cacheManager.getCacheNames()
                  .parallelStream()
                  .forEach(n -> cacheManager.getCache(n).clear());
  }
  

  }

Suited

Have you verified onApplicationEvent is actually being triggered and you are able to get cache values in loop. ? – Salado

Do you see your cache name, if you print the result of cacheManager.getCacheNames()? It's possible the cache manager doesn't return any, on start up. As a test, try using @PostConstruct and cacheManger.getCache("your cache").clear(). – Kosiur

Answer 1

I was successfully able to clear the cache with ApplicationReadyEvent. As the CacheManager bean is available by the time, the cache is getting cleared properly on startup

@Autowired
private CacheManager cacheManager;

@EventListener
public void onApplicationEvent(ApplicationReadyEvent event) {
    cacheManager.getCacheNames()
                .parallelStream()
                .forEach(n -> cacheManager.getCache(n).clear());
}

Suited

Could you please provide me you cacheconfig class. I am implementing something similar to this and still facing some issue. – Sieber

Are you getting all cached data, because cacheManager.getCacheNames() doesn't return cached data. How you are getting? – Nevins

@senthil cacheManager.getCacheNames() returning empty data. How did this work for you ? I have same code – Octofoil

Answer 2

A simple practice to clear Redis DB at earlier life cycle stage. To config CacheManager @bean with argument RedisConnectionFactory passed in, calling flushDb() to delete all keys of the currently selected database before build up.

 @Bean
    public CacheManager cacheManager(RedisConnectionFactory redisConnectionFactory) {
        redisConnectionFactory.getConnection().flushDb(); //Delete all keys of the currently selected database
        return RedisCacheManager.builder(RedisCacheWriter.nonLockingRedisCacheWriter(redisConnectionFactory)).cacheDefaults(RedisCacheConfiguration.defaultCacheConfig()).build();
    }

Danseuse

Answer 3

For the Redis cache manager, if you want to clear the cache on boot, I think you will need to initialize the cache manager with a set of names. See the RedisCacheManagerBuilder docs

For example:

RedisCacheManagerBuilder.fromConnectionFactory(redisConnectionFactory)
                        .initialCacheNames(Set.of("cacheOne", "cacheTwo"))
                        .build();

Then you should be able to use @PostConstruct in you cache config class, for example.

@PostConstruct
public void clearCache() {
    cacheManager.getCacheNames()
                .parallelStream()
                .forEach(n -> cacheManager.getCache(n).clear());
}

Kosiur

Thanks for the suggestion. But I changed ContextRefreshedEvent listener to ApplicationReadyEvent listener, it worked properly – Suited

@Suited Cool, thanks for posting your solution as well. – Kosiur

Without initializing cache names is it possible to clear the cache? – Nevins