This currently just turns off validation of the kubelet cluster dns
flag, which should allow for experimenting with more complicated DNS
configurations such as local proxies, which may address shortcomings
of DNS retries with UDP.
Issue #5584
- switching to using code rather than a template for the systemd unit creation as requested in review
- as part of the review, changing the name of the ca from tls-ca to tls-client-ca
- changing the api from DisableAddressCheck to EnableAddressCheck and defaulting to true if no set
- fixing up the test for node-authorizer and shifting the parsing of the certificates as suggested in reviews to a method
a) The current implementation use's a static kubelet which doesn't not conform to the Node authorization mode (i.e. system:nodes:<nodename>)
b) As present the kubeconfig is static and reused across all the masters and nodes
The PR firstly introduces the ability for users to use bootstrap tokens and secondly when enabled ensure the kubelets for the masters as have unique usernames. Note, this PR does not attempt to address the distribution of the bootstrap tokens themselves, that's for cluster admins. One solution for this would be a daemonset on the masters running on hostNetwork and reuse dns-controller to annotated the pods and give as the DNS
Notes:
- the master node do not use bootstrap tokens, instead given they have access to the ca anyhow, we generate certificates for each.
- when bootstrap token is not enabled the behaviour will stay the same; i.e. a kubelet configuration brought down from the store.
- when bootstrap tokens are enabled, the Nodes sit in a timeout loop waiting for the configuration to appear (by third party).
- given the nodeup docker and manifests builders are executed before the kubelet builder, the assumption here is a unit file kicks of a custom container to bootstrap the rest.
- the current firewalls on between the master and nodes are fairly open so no need to open ports between the two
- much of the work was ported from @justinsb PR [here](https://github.com/kubernetes/kops/pull/4134/)
- we add a very presumptuous server and client certificates for use with an authorizer (node-bootstrap-internal.dns_zone)
I do have an additional PR which performs the entire thing. The process being a node_authorizer which runs on the master nodes via a daemonset, the service implements a series of authorizers (i.e. alwaysallow, aws, gce etc). For aws, the process is similar to how vault authorizes nodes [here](https://www.vaultproject.io/docs/auth/aws.html). Nodeup no then calls out to the node_authorizer on bootstrap and provisions the kubelet.
We also have to stop passing the flag on ContainerOS, because it's set
in /etc/docker/default.json and it's now an error to pass the flag.
That in turn means we move those options to code, which are the last of
those legacy config options. (We still have a few tasks declaratively
defined though)
Kubernetes 1.9 changed the default for etcd-quorum-read flag value to
true, in the hope of fixing some of the edge-case controller issues.
However, while this is cheap on etcd3, that fix was not backported to
etcd2, and performance there of quorum reads is poor.
For non-HA clusters with etcd2, it still goes through raft, but does not
need to - we set etcd-quorum-read to false, as this is just a missed
optimization in etcd2.
For HA clusters with etcd2, it's trickier, but at least for now we're
going to avoid the (crippling) performance regression. kops 1.10 should
have etcd-manager (allowing upgrades to etcd3), and the ability to
configure IOPS on the etcd volume, so we can revisit this in 1.10 /
1.11.
Justin SB
k8s-ci-robot
Rohith
Justin Santa Barbara
andrewsykim
Spike Curtis
Mike Splain
Tomas Virgl
Ripta Pasay
Davanum Srinivas
James McMinn
Maciej Kwiek