Bug 1963079

Summary:	KCM/KS: ability to enforce localhost communication with the API server.
Product:	OpenShift Container Platform	Reporter:	Lukasz Szaszkiewicz <lszaszki>
Component:	kube-controller-manager	Assignee:	Lukasz Szaszkiewicz <lszaszki>
Status:	CLOSED ERRATA	QA Contact:	zhou ying <yinzhou>
Severity:	high	Docs Contact:
Priority:	high
Version:	4.8	CC:	aos-bugs, mfojtik
Target Milestone:	---
Target Release:	4.8.0
Hardware:	Unspecified
OS:	Unspecified
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Last Closed:	2021-07-27 23:09:41 UTC	Type:	Bug
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
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Embargoed:

Description Lukasz Szaszkiewicz 2021-05-21 11:41:43 UTC

For the past months, we have been involved in many escalations that showed a misconfigured load balancer can cause a significant outages. One quick way of ruling a malfunctioning LB is to switch affected components to use localhost to communicate with Kube API.

We are going to use this BZ to merge a few PRs for KCM and KC to allow that. Once they merge the support engineers will have an easy way of enforcing localhost communication.

Comment 2 zhou ying 2021-06-01 10:56:18 UTC

Check for the KCM，  :
[root@localhost ~]# oc get kubecontrollermanager cluster -o yaml 
apiVersion: operator.openshift.io/v1
kind: KubeControllerManager
...
spec:
  logLevel: TraceAll
...
  unsupportedConfigOverrides:
    extendedArguments:
      master:
      - https://api-int.yinzhou601.qe.devcluster.openshift.com:1234
      unsupported-kube-api-over-localhost:
      - "true"

when setting with invalid api, still works well. 

Check for the KS:
[root@localhost ~]# oc get kubescheduler cluster -o yaml 
apiVersion: operator.openshift.io/v1
kind: KubeScheduler
....
spec:
  logLevel: TraceAll
...
  unsupportedConfigOverrides:
    arguments:
      master:
      - https://api-int.yinzhou601.qe.devcluster.openshift.com:1234/
      unsupported-kube-api-over-localhost:
      - "true"

when setting with invalid api, ks still works well.

Comment 5 errata-xmlrpc 2021-07-27 23:09:41 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Moderate: OpenShift Container Platform 4.8.2 bug fix and security update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2021:2438