cmd/compute-domain-daemon: non-converging CD status due to lost node updates

[aditighag]

When multiple compute-domain daemon pods update ComputeDomain status from their own view of the object, syncNodeInfoToCD rewrites the full status.nodes list and can drop a peer node entry. The CD status fails to converge.

Add a unit test that reproduces this lost-update behavior by simulating two daemon instances reading the same initial ComputeDomain object and then writing their node info sequentially.

Snippets from a real cluster deployment highlighting the bug -

Status:
  Nodes:
    Clique Id: 9f410827-489f-46fd-8203-51266ca08eb7.32766
    Index: 0
    Ip Address: 10.42.3.138
    Name: cluster1-mgx-00011
    Status: NotReady
    Clique Id: 9f410827-489f-46fd-8203-51266ca08eb7.32766
    Index: 1
    Ip Address: 10.42.1.100
    Name: cluster1-mgx-00017
    Status: NotReady
  Status: NotReady
Events: <none>

I0415 16:14:28.038085 1 cdstatus.go:276] Successfully inserted/updated node in CD (nodeinfo: &{cluster1-mgx-00011 10.42.3.138 9f410827-489f-46fd-8203-51266ca08eb7.32766 0 NotReady})
I0415 16:14:28.038098 1 cdstatus.go:339] numNodes: 2, nodes seen: 1
I0415 16:14:28.044285 1 cdstatus.go:239] syncNodeInfoToCD noop: pod IP unchanged (10.42.3.138)
I0415 16:14:28.044300 1 cdstatus.go:339] numNodes: 2, nodes seen: 1
I0415 16:14:28.053413 1 cdstatus.go:239] syncNodeInfoToCD noop: pod IP unchanged (10.42.3.138)
I0415 16:14:28.053424 1 cdstatus.go:354] IP set for clique did not change

I0415 16:14:30.033811 1 cdstatus.go:259] CD status does not contain node name 'cluster1-mgx-00011' yet, try to insert myself: &{cluster1-mgx-00011 9f410827-489f-46fd-8203-51266ca08eb7.32766 0 NotReady}
I0415 16:14:30.037427 1 round_trippers.go:632] "Response" verb="PUT" url="https://10.43.0.1:443/apis/resource.nvidia.com/v1beta1/namespaces/default/computedomains/imex-channel-injection/status" status="200 OK" milliseconds=3
I0415 16:14:30.037620 1 cdstatus.go:276] Successfully inserted/updated node in CD (nodeinfo: &{cluster1-mgx-00011 10.42.3.138 9f410827-489f-46fd-8203-51266ca08eb7.32766 0 NotReady})
I0415 16:14:30.037656 1 cdstatus.go:339] numNodes: 2, nodes seen: 1
I0415 16:14:30.042979 1 cdstatus.go:239] syncNodeInfoToCD noop: pod IP unchanged (10.42.3.138)
I0415 16:14:30.042995 1 cdstatus.go:339] numNodes: 2, nodes seen: 1
I0415 16:14:30.052870 1 cdstatus.go:239] syncNodeInfoToCD noop: pod IP unchanged (10.42.3.138)
I0415 16:14:30.052888 1 cdstatus.go:354] IP set for clique did not change

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• ✅ login: aditighag / name: Aditi Ghag (8489b57)

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[ArangoGutierrez]

The repro is clean and the race is real. A few notes on the test shape before this lands.

1. noopMutationCache hides what a fix needs to do. Calling syncNodeInfoToCD directly with a no-op mutation cache exposes the writer race, but a fix that relies on the mutation cache (reading back the server's post-write object in onAddOrUpdate → m.Get()) is indistinguishable from a fix that just adds retry-on-conflict in the writer — both pass. Consider a second test that drives onAddOrUpdate through the real NewIntegerResourceVersionMutationCache and asserts a stale inbound UPDATE does not overwrite fresher state.

2. N=2 scenario only. The repro has two writers. The production failure mode is N writers racing after an informer resync burst. A fix that serializes only two writers (local mutex, etc.) would pass this test and still break at scale. Suggest parameterising on N, or asserting "all N entries survive" as the invariant.

3. Test-only PR, CI implications. This is the first _test.go under cmd/compute-domain-daemon/. If that path is on the default go test / make test, merging leaves CI red. Either land the fix in the same PR, or gate the repro behind t.Skip("tracked in #<issue>") with a follow-up issue.

4. Design question for the fix (non-blocking here). Full-object UpdateStatus from a stale snapshot is racy by construction. Two idiomatic paths: retry.RetryOnConflict with a ResourceVersion precondition, or a targeted patch that mutates only this daemon's own .status.nodes[i] entry. The latter eliminates the class of bug rather than retrying around it. Worth calling out in the fix PR so reviewers can anchor on one model.

Requesting changes pending the fix + broader-N test.

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[aditighag]

2. N=2 scenario only. The repro has two writers. The production failure mode is N writers racing after an informer resync burst. A fix that serializes only two writers (local mutex, etc.) would pass this test and still break at scale. Suggest parameterising on N, or asserting "all N entries survive" as the invariant.

Sure, I'll extend the test by parameterizing numofNodes.

3. Test-only PR, CI implications. This is the first _test.go under cmd/compute-domain-daemon/. If that path is on the default go test / make test, merging leaves CI red. Either land the fix in the same PR, or gate the repro behind t.Skip("tracked in #") with a follow-up issue.

I can take a stab at the fix in a follow-up PR. Any objections to merging this PR that adds a unit test repro for the bug?

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[aditighag]

@ArangoGutierrez Addressed review comments in the latest push. PTAL!

[aditighag]

@ArangoGutierrez Ping? :)

[dims]

/ok-to-test
/release-note-none

[dims]

/assign @shivamerla

[guptaNswati]

test failure is a flake.

[aditighag]

@dims / @guptaNswati

test failure is a flake.

Could you re-trigger the test? Thanks!

[dims]

/retest