kubernetes: Masters should not be excluded from service load balancers

Is this a BUG REPORT or FEATURE REQUEST?: /kind bug

What happened: I’m running a single node cluster on AWS EC2, ie. scheduling work on the master as well. Now that I tried to add an ELB for my service, the EC2 instance is not associated with the ELB. The ELB gets created but there are 0 EC2 instances associated with it. I’m using ELB for SSL termination, if you wonder why I’d like to load balance a single node cluster.

The service controller logs this message:

I0628 17:54:48.853175       1 event.go:221] Event(v1.ObjectReference{Kind:"Service", Namespace:"default", Name:"nginx", UID:"59980933-7afc-11e8-9a8c-0621b993d602", APIVersion:"v1", ResourceVersion:"2052", FieldPath:""}): type: 'Warning' reason: 'UnAvailableLoadBalancer' There are no available nodes for LoadBalancer service default/nginx

What you expected to happen: The EC2 instance is associated with the ELB.

How to reproduce it (as minimally and precisely as possible):

• Boot an EC2 instance with correct IAM permissions
• Install a single node cluster using kubeadm and cloud-provider=aws
• Untaint the node
• Schedule eg. nginx
• Create an external load balancer for nginx
• View the ELB in AWS console and note the Status: 0 of 0 instances in service

Anything else we need to know?: The reason for this seems to be the node-role.kubernetes.io/master label. This blocks associating a load balancer with the node. On the other hand this changed what is included, because includeNodeFromNodeList did not check if a node is a master. I’m not sure what would be correct fix. I could try submit a PR, if you guide me how this should behave. Is my scenario even a supported one?

I think this bug should be reproducible on other clouds as well.

Environment:

• Kubernetes version (use kubectl version):

Client Version: version.Info{Major:"1", Minor:"11", GitVersion:"v1.11.0", GitCommit:"91e7b4fd31fcd3d5f436da26c980becec37ceefe", GitTreeState:"clean", BuildDate:"2018-06-27T20:17:28Z", GoVersion:"go1.10.2", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"11", GitVersion:"v1.11.0", GitCommit:"91e7b4fd31fcd3d5f436da26c980becec37ceefe", GitTreeState:"clean", BuildDate:"2018-06-27T20:08:34Z", GoVersion:"go1.10.2", Compiler:"gc", Platform:"linux/amd64"}

• Cloud provider or hardware configuration: AWS
• OS (e.g. from /etc/os-release):

PRETTY_NAME="Debian GNU/Linux 9 (stretch)"
NAME="Debian GNU/Linux"
VERSION_ID="9"
VERSION="9 (stretch)"
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"

• Kernel (e.g. uname -a):

Linux ip-x.eu-central-1.compute.internal 4.9.0-6-amd64 #1 SMP Debian 4.9.88-1+deb9u1 (2018-05-07) x86_64 GNU/Linux

• Install tools: kubeadm