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PO to GMP Migration Tool: Service Resolution Functions - #2002

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karthunni/po-migrate-refactorfrom
karthunni/po-migrate-service-resolution
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PO to GMP Migration Tool: Service Resolution Functions#2002
karthunni wants to merge 5 commits into
karthunni/po-migrate-refactorfrom
karthunni/po-migrate-service-resolution

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This PR implements the core service and port resolution helper functions in pkg/migrate/helpers.go required for the upcoming ServiceMonitor migration work.

Key additions:

  • findServicesBySelector: Traverses the ResourceCache to return Service CRs matching a specified LabelSelector within target namespaces.
  • resolveServicePort: Inspects a Service's spec.ports list to map a target port reference (either a string name or a port number) to the Pod's actual container targetPort value.
  • convertServiceTargetLabels: Maps Service-level labels (as defined in spec.targetLabels of ServiceMonitor) to static metric relabeling rules (action: replace), appending the "exported_" prefix if it clashes with protected Prometheus labels.
  • Added comprehensive unit tests in helpers_test.go verifying all helper behaviors, error paths, and edge cases.

@karthunni karthunni self-assigned this Jul 24, 2026

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Code Review

This pull request introduces helper functions in pkg/migrate/helpers.go along with comprehensive unit tests in pkg/migrate/helpers_test.go to find Services by selector, resolve Service ports to target ports, and convert Service target labels to static metric relabeling rules. The reviewer provided valuable feedback, suggesting a nil check for the ResourceCache receiver to prevent panics, an explicit check for empty port strings to avoid accidental matches with unnamed ports, and handling additional numeric types (float64 and int) in the targetPort type switch to ensure robust parsing of unstructured objects.

Comment thread pkg/migrate/helpers.go Outdated
Comment thread pkg/migrate/helpers.go
Comment thread pkg/migrate/helpers.go Outdated
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/gemini review

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Code Review

This pull request introduces helper functions in pkg/migrate/helpers.go—including findServicesBySelector, resolveServicePort, and convertServiceTargetLabels—along with comprehensive unit tests to support Kubernetes Service resolution and label mapping during migration. The review feedback highlights that resolveServicePort uses a fragile type assertion for port numbers in unstructured objects and incorrectly propagates fatal errors instead of logging warnings and falling back to the port string. Consequently, the reviewer suggests refactoring resolveServicePort to handle type coercion safely and return fallbacks, and updating the unit tests accordingly.

Comment thread pkg/migrate/helpers.go
Comment thread pkg/migrate/helpers_test.go
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/gemini review

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Code Review

This pull request adds helper functions to find services by selector, resolve service ports to target ports, and convert service target labels to relabeling rules, along with comprehensive unit tests. The feedback suggests improving the robustness of the service port resolution by logging a warning and using a placeholder instead of returning a fatal error when encountering a malformed port, which prevents the entire migration process from failing.

Comment thread pkg/migrate/helpers.go
@karthunni
karthunni force-pushed the karthunni/po-migrate-service-resolution branch from 6d133c9 to 648b3e1 Compare July 24, 2026 19:33
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/gemini review

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Code Review

This pull request introduces helper functions to find services by selector, resolve service ports to target ports, and map service labels to metric relabeling rules, along with their corresponding unit tests. Feedback suggests modifying resolveServicePort to log a warning and inject a placeholder port instead of returning a fatal error when encountering a malformed port entry, preventing the entire migration process from failing.

Comment thread pkg/migrate/helpers.go
@karthunni
karthunni force-pushed the karthunni/po-migrate-service-resolution branch from 648b3e1 to 8c87394 Compare July 27, 2026 19:17
@karthunni
karthunni force-pushed the karthunni/po-migrate-service-resolution branch from 60e7cdc to 436c631 Compare July 28, 2026 15:36
@dashpole dashpole self-assigned this Jul 29, 2026
@karthunni
karthunni marked this pull request as ready for review July 29, 2026 20:46
@karthunni
karthunni force-pushed the karthunni/po-migrate-service-resolution branch from 436c631 to 4bdfc9f Compare July 29, 2026 21:07
@karthunni
karthunni requested a review from bernot-dev July 29, 2026 21:52
Comment thread pkg/migrate/helpers.go
}

// findServicesBySelector finds Services matching the selector in target namespaces (all if empty).
func (c *ResourceCache) findServicesBySelector(selector metav1.LabelSelector, namespaces []string) ([]*unstructured.Unstructured, error) {

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PR Scope Note: This PR diffs against main at 2,371 lines / 41 commits because its base is the unmerged karthunni/po-migrate-refactor branch. Retargeting the PR base to karthunni/po-migrate-refactor would isolate the 5 commits (~485 lines) specific to service resolution.

Comment thread pkg/migrate/helpers.go
continue
}

target := l

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convertServiceTargetLabels uses raw Kubernetes Service label keys (such as app.kubernetes.io/name) as TargetLabel. Kubernetes label keys often contain dots and slashes, which are invalid in Prometheus label names. Sanitize non-alphanumeric characters to underscores first, then check protectedLabels against the sanitized name.

Comment thread pkg/migrate/helpers.go
return intstr.IntOrString{}, fmt.Errorf("failed to read port field: %w", err)
}
if !foundField {
return intstr.IntOrString{}, errors.New("service port spec is missing the port number")

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In resolveServicePort, encountering a port entry missing port or with an invalid type returns a fatal error immediately. If a Service has multiple ports and an earlier entry is malformed, resolving a valid target port later in the slice fails. Consider skipping malformed entries and returning an error only if no matching port is resolved.

Comment thread pkg/migrate/helpers.go
}

// asInt32 coerces various Go numeric types into an int32.
func asInt32(val any) (int32, bool) {

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asInt32 converts int64 and float64 to int32 without bounds or range checks. Out-of-range values like 4294967297 truncate to 1 and can match the wrong port. Consider adding range validation for [1, 65535].

Comment thread pkg/migrate/helpers.go
}

// targetPort can be int, float64, or string.
if valStr, ok := targetPort.(string); ok {

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targetPort: "" returns intstr.FromString("") without validation, while numeric zero falls back to portNum. Empty string targetPorts should be treated as invalid or fall back to portNum.

Labels: labels,
},
}
u, _ := runtime.DefaultUnstructuredConverter.ToUnstructured(svc)

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addServiceToCache, makeTestService, and makeTestServiceWithLabels can be consolidated into a single builder taking labels and ports. Also, u, _ := swallows ToUnstructured conversion errors instead of using t.Fatal or returning the error.

if len(got) != len(tc.expected) {
t.Fatalf("expected %d rules, got %d", len(tc.expected), len(got))
}
for i, r := range got {

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TestConvertServiceTargetLabels manually compares fields one-by-one. Using cmp.Diff (as done elsewhere in helpers_test.go) improves assertion readability and diff diagnostic quality.

Comment thread pkg/migrate/helpers.go
}

// findServicesBySelector finds Services matching the selector in target namespaces (all if empty).
func (c *ResourceCache) findServicesBySelector(selector metav1.LabelSelector, namespaces []string) ([]*unstructured.Unstructured, error) {

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Parent Branch Bug Note (in convertRelabelingToMetricRelabeling): targetLabels.fromPod appends LabelMapping{From: p} without renaming protected labels to exported_<label>, unlike the sibling path. Pod labels matching protected labels (like job) cause operator validation failure.

Comment thread pkg/migrate/helpers.go
}

// findServicesBySelector finds Services matching the selector in target namespaces (all if empty).
func (c *ResourceCache) findServicesBySelector(selector metav1.LabelSelector, namespaces []string) ([]*unstructured.Unstructured, error) {

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Parent Branch Bug Note (in shouldSkipRelabelConfig): shouldSkipRelabelConfig lists labelkeep as supported, promoting it to metricRelabeling where it drops protected labels like __address__, cluster, namespace. Pre-scrape labelkeep/labeldrop act on __meta_* labels and should be dropped with a warning rather than promoted.

Comment thread pkg/migrate/helpers.go
}

// findServicesBySelector finds Services matching the selector in target namespaces (all if empty).
func (c *ResourceCache) findServicesBySelector(selector metav1.LabelSelector, namespaces []string) ([]*unstructured.Unstructured, error) {

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Parent Branch Bug Note (in convertSecretSelector): convertSecretSelector sets Namespace: c.namespace on secret references, but PodMonitoring CEL rules strictly forbid Namespace on secret references ("Namespace not allowed on PodMonitoring secret references.").

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