How to minimize interaction with Redis when using it as a Spring Session cache? - spring-boot

Question

We are using Spring Cloud Gateway for OAuth2 authentication, after which it stores users session information in Redis with default settings set by #EnableRedisWebSession and
#Bean
fun redisConnectionFactory(): LettuceConnectionFactory {
return LettuceConnectionFactory("redis-cache", 6379);
}
#Bean
fun authorizedClientRepository(): ServerOAuth2AuthorizedClientRepository {
return WebSessionServerOAuth2AuthorizedClientRepository()
}
application.yml cache settings:
spring:
session:
store-type: redis
redis:
save-mode: on_set_attribute
flush-mode: on_save
It works fine, though I can see it makes requests to Redis on every user requests like it doesn't have in-memory cache at all. Is there any option to change this behaviour (i.e. make requests though the network to Redis only if current user session is not found in local memory cache)? May be I can reimplement some classes or there is no way to do it except of rewriting all cache logic? Sorry, for quite a broad question, but I didn't find any information on this topic in the documentation. Or maybe you could point me at classes in Spring Session source code, where this logic is implemented, so I could figure out what are my options.
I'm using spring-cloud-starter-gateway 2.2.5.RELEASE, spring-session-core 2.3.1.RELEASE, spring-boot-starter-data-redis-reactive and spring-session-data-redis.

Answer 1

From reading the documentation, I don't believe it is possible out of the box as using a local cache could result in inconsistent state amongst all connecting SCG instances to that Redis Instance.
You would need to define your own implementation of a SessionRepository that will try a local caffeine cache, and if not found then go to Redis instead. As a starting point, you could duplicate or trying extending the RedisSessionRepository.
The only thing you'd need to be careful of then is if you have multiple instances of SCG running how to handle if another instance updates redis, how the other instances would handle it if they have a locally cached instance already.