Clear Redis Cache on Spring Boot Application Startup - spring

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());
}
}

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());
}

Answer 2

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());
}

Answer 3

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();
}