Bug 2086461 - CNO probes MTU unnecessarily in Hypershift, making cluster startup take too long
Summary: CNO probes MTU unnecessarily in Hypershift, making cluster startup take too long
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: OpenShift Container Platform
Classification: Red Hat
Component: Networking
Version: 4.11
Hardware: Unspecified
OS: Unspecified
medium
medium
Target Milestone: ---
: 4.11.0
Assignee: aaleman
QA Contact: Ross Brattain
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2022-05-16 08:45 UTC by Casey Callendrello
Modified: 2022-08-10 11:12 UTC (History)
1 user (show)

Fixed In Version:
Doc Type: If docs needed, set a value
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Clone Of:
Environment:
Last Closed: 2022-08-10 11:12:00 UTC
Target Upstream Version:
Embargoed:

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Links
System ID Private Priority Status Summary Last Updated
Github openshift cluster-network-operator pull 1441 0 None open Bug 2086461: AWS: Use hardcoded MTU to speed up cluster creation 2022-05-16 08:46:01 UTC
Github openshift cluster-network-operator pull 1454 0 None open Bug 2086461: Hypershift: Also add default for Azure mtu 2022-05-19 19:05:32 UTC
Red Hat Product Errata RHSA-2022:5069 0 None None None 2022-08-10 11:12:11 UTC

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
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