Metallb: using layer2 is it possible to see which of the Kubernetes worker nodes is the primary?

[nodesocket]

First, huge thanks 👏 for MetalLB. I've been researching various LoadBalancer solutions when running Kubernetes on-premises and everything was horribly complicated until I came across MetalLB.

Using layer2 according to the documentation:

In layer 2 mode, one machine in the cluster takes ownership of the service

• Is it possible to see which worker node in the Kubernetes cluster is the primary for MetalLB?
• Secondly, if I want to perform scheduled maintenance on the primary worker node for MetalLB is there a way to manually switch to another Kubernetes worker node for MetalLB?

[jenciso]

In order to see the current worker node, I could use this command
kubectl describe svc name_service. E.g.

kubectl describe svc -n istio-system istio-ingressgateway ... External Traffic Policy: Cluster Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal IPAllocated 36m metallb-controller Assigned IP "10.64.13.130"
And to answer the second question.

First, I need to cordon the node (using kubectl cordon nodename) and then I should be move the pod using kubectl delete pod ....,

E.g.

[root@dcbvm090lb321 istio]# kubectl delete pod -n istio-system istio-ingressgateway-dfbdff6cc-l2jbm                                                                                                                
pod "istio-ingressgateway-dfbdff6cc-l2jbm" deleted                                                                                                                                                                 
[root@dcbvm090lb321 istio]# 

Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal IPAllocated 44m metallb-controller Assigned IP "10.64.13.130" Normal nodeAssigned 3m11s (x4 over 43m) metallb-speaker announcing from node "dcbvm090lb342.e-unicred.com.br" Normal nodeAssigned 112s metallb-speaker announcing from node "dcbvm090lb342.e-unicred.com.br" Normal nodeAssigned 10s (x3 over 13s) metallb-speaker announcing from node "dcbvm090lb341.e-unicred.com.br"

[adampl]

Well, what if you don't have istio?

[danderson]

This has nothing to do with istio. If you kubectl describe service on any LoadBalancer service, there is an event recorded that specifies who the announcing node is.

You can't move the announcer ahead of scheduled maintenance. The assignment of the announce is done in a distributed fashion, so there's no central point that you can tell "okay switch now". Failover will happen during the node drain.

[anton-johansson]

@danderson, sorry to revive an old issue. Is there a technical limitation that makes it impossible to force MetalLB to change the announcing node? It feels a bit hassly to cordon, delete all pods on the node that are exposed with LoadBalancer, then perform the maintenance and then uncordon.

It would be really nice if you could tell MetalLB to avoid a node, maybe through an API? That way, I don't really need to find all the pods that I need to delete (it could be a few).

[anton-johansson]

@danderson, sorry for shameless bumps!

But I still feel it's a bit weird to have to delete perfectly fine pods in order to "fail over" the announced IP address. Is there any way that a "force" could be introduced?

[johananl]

It would be really nice if you could tell MetalLB to avoid a node, maybe through an API? That way, I don't really need to find all the pods that I need to delete (it could be a few).

@anton-johansson we can re-evaluate this. I think it would be best if you could open a new issue describing the desired functionality in as much detail as possible. This will help us figure out if it's reasonable to implement. If there is an alternative solution (e.g. kubectl drain) which kind of works but in your opinion isn't good enough, it would be very helpful if you could explain why such a solution doesn't work for you.

In general we do our best to ensure a requested functionality is generic (i.e. it doesn't address a very "specialized" use case) and can be integrated into MetalLB in a reasonable way, i.e. without interacting negatively with other features and/or radically changing the project's design.

[anton-johansson]

Thanks for the reply @johananl, I'll submit a new issue with the request.