Consider Supporting Redis with CRaC

[charlie-harvey]

Feature description

import io.lettuce.core.RedisClient
import io.micronaut.crac.OrderedResource
import jakarta.inject.Named
import jakarta.inject.Singleton
import mu.KotlinLogging
import org.crac.Context
import org.crac.Resource

private val logger = KotlinLogging.logger {}

@Singleton
class RedisResource(
    @Named("redisClientA") private val redisClientA: RedisClient,
    @Named("redisClientB") private val redisClientB: RedisClient
) : OrderedResource {

    override fun beforeCheckpoint(context: Context<out Resource>?) {
        logger.info { "stopping redis clients before checkpoint" }
        redisClientA.shutdown()
        redisClientB.shutdown()
        logger.info { "done stopping redis clients before checkpoint" }
    }

    override fun afterRestore(context: Context<out Resource>?) {
        logger.info { "starting redis clients after restore (just logging for now)" }
        logger.info { "done starting redis clients after restore (just logging for now)" }
    }
}

This is what I have. But I'm really not sure if its right. I looked at the Hikari one but the RedisClient doesn't have as many methods. Just .shutdown() and .connect(). And .connect() in the afterRestore() doesn't do what I expect. I think the client is already started and connected so the .connect() fails.

Do I actually even need this OrderedResource? I'm not sure. Do the clients need to be shut down? Does someone else know more about this than I do? I hope so.

Thanks!

[timyates]

Hiya!

I'm working on a more general fix for Redis over here #78

The clients need to be closed, so that the checkpoint can be successfully taken, however as you've seen there's no way of "pausing" and "resuming" connections to Redis (which are StatefulRedisConnection objects based on Netty)

So in the above PR, what I'm doing is destroying the beans before the checkpoint. Then, so long as the Service which makes use of the beans is @Refreshable, the client should be re-created on restore.

It's working under test, and I'm now checking that it also works in a real application

/me brushes dust off his x86 machine

[timyates]

Fixed by #78 and released in v1.2.1

[rjaros87]

Hi @timyates,
Does your solution also support StatefulRedisPubSubConnection ?

For StatefulRedisConnection & @Refreshable annotation it works, but StatefulRedisPubSubConnection connection for me is still closed :/

[timyates]

Hi @rjaros87 thanks for the report!

This should fix it: #91

[rjaros87]

I've created separate issue for that #89. I will check it later and close.

[fhoner]

Hi @timyates , is something similar planned for MongoDB?

[timyates]

Can you raise an issue? And as always, PRs welcome 😉