[target allocator] Avoid disruptions with default PDB

[cmergenthaler]

Component(s)

target allocator

Is your feature request related to a problem? Please describe.

In order to ensure HA for the target allocator when running with > 1 replicas, the operator should manage a default PodDisruptionBudget for the target allocator. Since it is recommended to run the TA with at least 2 replicas to ensure HA, this should be addressed. In case of a node/cluster upgrade, k8s might disrupt all running TA's at the same time, which would result in a non-HA target allocator.
With work being done on #2141, a PDB for the collector has been added already.

Describe the solution you'd like

Similar to #2141, a default PDB with maxUnavailable=1 should be created for the TA by the operator by default.

Describe alternatives you've considered

No response

Additional context

https://kubernetes.io/docs/tasks/run-application/configure-pdb/

[JorTurFer]

It seems that I misunderstood the TA when I supported PDB on the collector, but if it's an HA component, I'm willing to add the PDB to it too

[jaronoff97]

@JorTurFer would you be able to work on this?

[JorTurFer]

Yes I am, assign it to me and I'll try to do it this weekend. Is TA an HA component?

[jaronoff97]

yes, but only if the consistent-hashing strategy is set! So maybe we should only set this if that strategy is set. This actually pairs nicely with #1105 which I think would be good to do with this too. i.e. make the strategy an actual type, not just a kube builder enum and check if that type is set to consistent hashing in which case we should make a PDB with it.

[JorTurFer]

yes, but only if the consistent-hashing strategy is set! So maybe we should only set this if that strategy is set. This actually pairs nicely with #1105 which I think would be good to do with this too. i.e. make the strategy an actual type, not just a kube builder enum and check if that type is set to consistent hashing in which case we should make a PDB with it.

I've just added the PDB if the strategy is set because I don't have enough context for changing the strategy part, sorry :/
I could try to update it, but I'm not sure when I can address it

[jaronoff97]

no problem! I can do that in a follow up. Thank you!

[cmergenthaler]

@JorTurFer Thanks for your work! @jaronoff97 the issue can be closed right?

[jaronoff97]

yep! Thank you so much @JorTurFer

[JorTurFer]

no worries, happy to help :)