Redis Sentinel support

[bootc]

Our production Redis clusters use Sentinel for High Availability. Please add Sentinel support so that Icinga DB can automatically route requests to active nodes in the cluster as necessary.

[lippserd]

Team, does anyone know what specifics we need to change to support this?

[julianbrost]

On the Go side, this should be rather trivial as the lib we use supports that, we'd just have to create the client: https://pkg.go.dev/github.com/go-redis/redis/v8#NewFailoverClient

However, on the C++ side, we'd have to implement all that failover stuff. I don't know how complex that would be.

Also, the current HA model for Icinga 2 + Icinga DB expects one Redis server per Icinga 2 instance, so if you want HA, you just add a second Redis instance. Also note that even if we supported this, you couldn't have two Icinga 2 instances write into the same cluster.

So I don't really see a benefit for Icinga DB in supporting this right now.

[Al2Klimov]

one Redis server per Icinga 2 instance

... which ideally runs on the same machine as Icinga 2, so IMAO that feature just doesn’t fit in our concept.

[yoshi314]

can an external redis cluster be used? i typically use redis-ha cluster in k8s for redis backends.

[julianbrost]

If it acts like a standard Redis server, it will be fine. I don't know if that's the case. Is redis-ha the same thing as Redis Sentinel?

[yoshi314]

it's composed of optional haproxy frontend (to manage connections from outside of k8s) and 3 nodes with sentinel.

[Al2Klimov]

Wait. If a Redis sentinel cluster can be frontended by a HAproxy, one could also use shuffling DNS or iptables. So we don’t necessarily have to support this by ourselves.