feat: Add Valkey Sentinel & HAProxy support in High Availability setup.

[khtee]

Feat #22

[dmaes]

Nice work!

I have some notes/questions:

• You'll want to disable the default statefulset when sentinel is enabled.
• Do you plan on adding a HAProxy deployment, so clients don't have to be aware of sentinel? ( See for example https://arystech.com/blog/setting-up-haproxy-with-redis-sentinel-for-high-availability-on-microk8s-kubernetes )

[khtee]

Nice work!

I have some notes/questions:

• You'll want to disable the default statefulset when sentinel is enabled.
• Do you plan on adding a HAProxy deployment, so clients don't have to be aware of sentinel? ( See for example https://arystech.com/blog/setting-up-haproxy-with-redis-sentinel-for-high-availability-on-microk8s-kubernetes )

Good points! Will work on both improvements.

[yoannrt]

Good job,

I have some questions too,
I assume to discover who is master, you have to ask sentinel SENTINEL GET-MASTER-ADDR-BY-NAME mymaster ?
(Currently, the replica service is sticked to pod-0 in the STS)

Also, would that make sense to run sentinel as a side container in the replica STS pods ?

[amontalban]

Thank you @khtee can't wait to get this merged in 🙏

[dmaes]

Also, would that make sense to run sentinel as a side container in the replica STS pods ?

You'll want to disable the default statefulset when sentinel is enabled

I got confused, thinking valkey-sentinel also runs the server process, it's been a while since I used redis/valkey. But yes, @khtee you'll want to run sentinel and the server side-to-side in the same pod, don't split them out in different statefulsets.

[yoannrt]

Do you plan on adding a HAProxy deployment, so clients don't have to be aware of sentinel?

@dmaes I guess when you suggest to implement HAproxy, it's for sentinel incompatible clients workloads ?
So this would be optional and the default implementation would be a valkey/sentinel HA setup ?

[khtee]

Also, would that make sense to run sentinel as a side container in the replica STS pods ?

You'll want to disable the default statefulset when sentinel is enabled

I got confused, thinking valkey-sentinel also runs the server process, it's been a while since I used redis/valkey. But yes, @khtee you'll want to run sentinel and the server side-to-side in the same pod, don't split them out in different statefulsets.

Added following enhancements.

• Sentinel now runs as a sidecar in valkey pod.
• HAProxy with sidecar watcher to track failover.

[dmaes]

Do you plan on adding a HAProxy deployment, so clients don't have to be aware of sentinel?

@dmaes I guess when you suggest to implement HAproxy, it's for sentinel incompatible clients workloads ? So this would be optional and the default implementation would be a valkey/sentinel HA setup ?

That's correct.

The truly kubernetes-native way would probably be to have a sentinel-master Service, using a sentinel.valkey.io/master: "true" label selector, and then some watcher that updates that label on the correct Pod,
but a HAproxy deployment is the easier option to implement, and is how most other Redis charts do it.