Bug 2086461

Summary:	CNO probes MTU unnecessarily in Hypershift, making cluster startup take too long
Product:	OpenShift Container Platform	Reporter:	Casey Callendrello <cdc>
Component:	Networking	Assignee:	aaleman
Networking sub component:	ovn-kubernetes	QA Contact:	Ross Brattain <rbrattai>
Status:	CLOSED ERRATA	Docs Contact:
Severity:	medium
Priority:	medium	CC:	rbrattai
Version:	4.11
Target Milestone:	---
Target Release:	4.11.0
Hardware:	Unspecified
OS:	Unspecified
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Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2022-08-10 11:12:00 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Casey Callendrello 2022-05-16 08:45:30 UTC

Because of the nature of the hypershift install flow, the time it takes CNO to probe MTU causes a lot of head-of-line blocking.

Now, in the general case, there's nothing we can do: we don't necessarily know the MTU of the worker nodes until they come online.

However, in certain cases, we can safely assume the MTU of the underlay, and remove this ~90 second delay.

Comment 5 Ross Brattain 2022-06-01 17:32:12 UTC

Verified on 4.11.0-0.nightly-2022-05-25-193227  AWS



268:[pod/cluster-network-operator-69b866655b-k6nl9/cluster-network-operator] I0601 13:20:41.719200       1 mtu_probe.go:44] AWS cluster, omitting MTU probing and using default of 9001
269:[pod/cluster-network-operator-69b866655b-k6nl9/cluster-network-operator] I0601 13:20:41.719223       1 log.go:195] Using detected MTU 9001
400:[pod/cluster-network-operator-69b866655b-k6nl9/cluster-network-operator] I0601 13:20:43.565223       1 mtu_probe.go:44] AWS cluster, omitting MTU probing and using default of 9001
401:[pod/cluster-network-operator-69b866655b-k6nl9/cluster-network-operator] I0601 13:20:43.565273       1 log.go:195] Using detected MTU 9001


It looks like MCO doesn't exist for the hosted cluster, so MTU migration of the hosted cluster is not supported.

Comment 7 errata-xmlrpc 2022-08-10 11:12:00 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 (Important: OpenShift Container Platform 4.11.0 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-2022:5069