How to deployed autoscale use statefulset ?

[laik]

as title. i saw the code related to deploying using a statefulset, but couldn't find the relevant documentation.

[laik]

For example: I changed it to sts under my test cluster and reconfigured the bucket to 3. It works.

➜  /tmp k  get leases -n knative-serving | grep autoscaler-bucket
autoscaler-bucket-00-of-03                                                                        autoscaler-0_10.244.0.17                                                     107s
autoscaler-bucket-01-of-03                                                                        autoscaler-0_10.244.0.17                                                     106s
autoscaler-bucket-02-of-03                                                                        autoscaler-2_10.244.16.27                                                    106s
➜  /tmp kg pod -o wide
NAME                                    READY   STATUS    RESTARTS   AGE   IP             NODE       NOMINATED NODE   READINESS GATES
...
autoscaler-0                            1/1     Running   0          99s   10.244.0.17    debian01   <none>           <none>
autoscaler-1                            1/1     Running   0          99s   10.244.32.11   debian03   <none>           <none>
autoscaler-2                            1/1     Running   0          99s   10.244.16.27   debian02   <none>           <none>
....

ref code :https://github.com/knative/serving/blob/main/cmd/autoscaler/main.go#L182

[dprotaso]

It's an advance deployment option (that's really poorly documented) - the idea it shards the key space of objects to reconcile and it become fixed to that ordinal.

Thus when an instance fails you know it's limited to that ordinal/keyspace. In contrast the default setup uses leases and those will transfer between deployment instances - it doesn't rebalance so it's sorta like a 'hot' standby. But specifically for the autoscaler the standby won't have up to date metrics (since we forward metrics only to the leader).

I need to dig out the old design document but you can see in this repo an example statefulset

https://github.com/mattmoor/mink/blob/b9148a39b2d8bbc69ca9aaf5e89a7613c0b179d8/config/core/deployments/controlplane.yaml#L15

In this instance they are also merging a whole whack of controllers into one binary. But again let me find the original design document that highlights how to do this.