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Support proxy_server_ready_backends metric #754

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Merged
merged 5 commits into from
Jul 3, 2025
Merged

Support proxy_server_ready_backends metric #754

merged 5 commits into from
Jul 3, 2025

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maqiuyujoyce
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@maqiuyujoyce maqiuyujoyce commented Jun 27, 2025 •
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Fixes #294
Prior art: #295

Added a new metric to track the total number of backends based on proxy strategy. To avoid circular import, I extracted out ProxyStrategy related types, functions and tests into a separate package.

I didn't overwrite the existent proxy_server_ready_backend_connections metric because of potential backwards compatibility concern brought up here: https://github.com/kubernetes-sigs/apiserver-network-proxy/pull/295/files#r872839718 Instead, I marked the problematic proxy_server_ready_backend_connections metric deprecated in the help message.

Tested locally following this example and got the following result when supporting both default and desthost backend managers:

# HELP konnectivity_network_proxy_server_ready_backend_connections Number of konnectivity agent connected to the proxy server
# TYPE konnectivity_network_proxy_server_ready_backend_connections gauge
konnectivity_network_proxy_server_ready_backend_connections 1
# HELP konnectivity_network_proxy_server_ready_backend_connections_total Total number of konnectivity agent connected to the proxy server
# TYPE konnectivity_network_proxy_server_ready_backend_connections_total gauge
konnectivity_network_proxy_server_ready_backend_connections_total{proxy_strategy="default"} 1
konnectivity_network_proxy_server_ready_backend_connections_total{proxy_strategy="destHost"} 1

Added unit tests for the new metric as well.

@k8s-ci-robot k8s-ci-robot added the cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. label Jun 27, 2025
@k8s-ci-robot k8s-ci-robot requested review from elmiko and tallclair June 27, 2025 03:12
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Hi @maqiuyujoyce. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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@k8s-ci-robot k8s-ci-robot added needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. size/M Denotes a PR that changes 30-99 lines, ignoring generated files. labels Jun 27, 2025
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jkh52 commented Jun 27, 2025

/ok-to-test

Did you consider using ProxyStrategy in the new metric? It would be nice to keep *Manager and *Storage types as implementation details. The proxy server already exposes --proxy-strategies to the cluster admin.

@k8s-ci-robot k8s-ci-robot added ok-to-test Indicates a non-member PR verified by an org member that is safe to test. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Jun 27, 2025
cheftako
cheftako reviewed Jun 27, 2025
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pkg/server/metrics/metrics.go Outdated
@@ -284,6 +299,11 @@ func (s *ServerMetrics) SetBackendCount(count int) {
s.backend.WithLabelValues().Set(float64(count))
}

// SetTotalBackendCount sets the total number of backend connection.
func (s *ServerMetrics) SetTotalBackendCount(managerName string, count int) {
s.totalBackendCount.WithLabelValues(managerName).Set(float64(count))
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Labels can generate cardinality issues. I don't think this is likely to be a problem but we can reassure/protect ourselves by changing managerName from a string (unbounded cardinality) to an enumeration with an observation on limiting the number of options.

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@maqiuyujoyce maqiuyujoyce Jun 27, 2025 •
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Done.

Based on @jkh52 's suggestion above, I used proxy strategy enum as the label. (Thank you @jkh52 !)
It introduced the circular dependency, so I extracted out ProxyStrategy related types and functions into a separate package, and many files were updated. I can split it out into a separate PR if you prefer!

@k8s-ci-robot k8s-ci-robot added size/L Denotes a PR that changes 100-499 lines, ignoring generated files. and removed size/M Denotes a PR that changes 30-99 lines, ignoring generated files. labels Jun 27, 2025
@maqiuyujoyce maqiuyujoyce mentioned this pull request Jun 28, 2025
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jkh52 commented Jun 30, 2025

I think there will remain a bug in ready_backend_connections (it gets clobbered when the server has more than one strategy). We could mark it deprecated (pkg/agent metrics has a help text example of this) if we think that will never get fixed.

@maqiuyujoyce maqiuyujoyce force-pushed the 202506-total-backend-metric branch from e72d63b to 565867c Compare July 1, 2025 21:10
@k8s-ci-robot k8s-ci-robot added size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. and removed size/L Denotes a PR that changes 100-499 lines, ignoring generated files. labels Jul 1, 2025
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I think there will remain a bug in ready_backend_connections (it gets clobbered when the server has more than one strategy). We could mark it deprecated (pkg/agent metrics has a help text example of this) if we think that will never get fixed.

Done.

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@jkh52 Also moved the tests into this PR according to your suggestion. Please take a look!

jkh52
jkh52 reviewed Jul 1, 2025
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pkg/server/metrics/metrics.go Outdated
prometheus.GaugeOpts{
Namespace: Namespace,
Subsystem: Subsystem,
Name: "ready_backend_connections_total",
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Final concern: the _total suffix here seems to contradict prometheus naming conventions (it implies a counter metric, not gauge).

Maybe just "ready_backends" or similar?

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Done.

@maqiuyujoyce maqiuyujoyce changed the title Support proxy_server_ready_backend_connections_total metric Support proxy_server_ready_backends metric Jul 2, 2025
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jkh52 commented Jul 3, 2025

/lgtm
/approve

@k8s-ci-robot k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Jul 3, 2025
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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jkh52, maqiuyujoyce

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@k8s-ci-robot k8s-ci-robot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Jul 3, 2025
@k8s-ci-robot k8s-ci-robot merged commit 71d3800 into kubernetes-sigs:master Jul 3, 2025
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[BUG] The backend ServerMetric is not correct
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