Project: [Redis] High availability based on Sentinel

[spa-87]

Currently KubeDB Redis engine supports two modes:

• standalone: when only one Pod is running
• cluster: sharding with minimum 3 masters and 1 replica for every master

But Redis supports an intermediate mode which isn't supported by KubeDB - high availability without sharding:
https://redis.io/topics/sentinel
https://redislabs.com/redis-features/high-availability

Here's a brief comparison of Redis Cluster with Sentinel (taken from https://alex.dzyoba.com/blog/redis-ha/)

Cluster Pros:
Shards data across multiple nodes
Has replication support
Has builtin failover of the master

Cluster Cons:
Not every library supports it
May not be as robust (yet) as standalone Redis or Sentinel
Introduces an extra network hop in case we missed the shard.

Our use-case:
We want to connect to Redis in Kubernetes from external servers. In order to expose Redis service we use corresponding feature of Nginx ingress controller (https://github.com/kubernetes/ingress-nginx/blob/master/docs/user-guide/exposing-tcp-udp-services.md). It provides a single entrypoint for working with Redis database. But "Cluster" mod requires direct connection to a particular Redis shard master IP and possibility to handle "MOVED" responses, what is unachievable for an external applications. Thus we have a single option - "standalone" mode which doesn't provide any availability guarantees.
If KubeDB Redis engine supported HA based on Sentinel, it would work perfectly for us.

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[walk1ng]

Hi Kubedb team,
We have the same feature request about this.
Our application run in external server and want to connect the kubedb/redis cluster in different k8s cluster, but as @spa-87 said, the 'redirect' and 'MOVED' should be blocked and failed due to unachievable network connection.
Do you have any plan/suggestion for this use-case?
Thanks a lot!

Hi @spa-87 ,
How do you work out the use-case(external connection) which you mentioned above now?
Could you please share your thought/method with me? I'm struggling with this.
Thanks a lot!

[SerialVelocity]

Same issue here.

Redis Cluster is not supported by harbor or rspamd but Redis Sentinel is supported by both.