Enable activedefrag in Redis

[kdambekalns]

Over time, Redis's memory allocation can become fragmented, especially in environments with a large number and variety of write, delete, and update operations. Redis 4.0 and newer versions include an active memory defragmentation feature, which helps in reclaiming unused memory and reducing fragmentation.

[kdambekalns]

But https://cloud.google.com/memorystore/docs/redis/memory-management-best-practices#manage_your_system_memory_usage_ratio says:

If the system memory usage ratio exceeds 80%, turn on activedefrag. Defragmentation can take hours to release fragmented memory. If write traffic is high, defragmentation alone may not be enough to stop your instance from running out of memory.

Maybe we should monitor "system memory usage ratio" first? Or do we follow the people at Redis Labs (https://serverfault.com/a/971879)?

Active defrag has a performance cost, sure, but it is almost always negligible. Although it is disabled by default in the OSS distro, we (Redis Labs) have been using in production for ages ;)

[kitsunet]

I think this is fine for our usage scenarios as we typical projects on beach do not use redis under high (computing) pressure.

[robertlemke]

I also think we can just go for it, however if possible, I would like that we run a local test setup where we trigger Redis so that we can really observe the difference.

[kdambekalns]

I'll do some tests using https://redis.io/docs/latest/operate/oss_and_stack/management/optimization/benchmarks/, might show something useful…